The I2C driver gets an interrupt upon transfer completion.
For multiple messages in a single transfer, N interrupts will be
received for N messages, leading to significant software interrupt
latency. To mitigate this latency, utilize Block Event Interrupt (BEI)
only when an interrupt is necessary. This means large transfers can be
split into multiple chunks of 8 messages internally, without expecting
interrupts for the first 7 message completions, only the last one will
trigger an interrupt indicating 8 messages completed.
By implementing BEI, multi-message transfers can be divided into
chunks of 8 messages, improving overall transfer time.
This optimization reduces transfer time from 168 ms to 48 ms for a
series of 200 I2C write messages in a single transfer, with a
clock frequency support of 100 kHz.
BEI optimizations are currently implemented for I2C write transfers only,
as there is no use case for multiple I2C read messages in a single transfer
at this time.
Signed-off-by: Jyothi Kumar Seerapu <quic_jseerapu@quicinc.com>
---
v1 -> v2:
- Moved gi2c_gpi_xfer->msg_idx_cnt to separate local variable.
- Updated goto labels for error scenarios in geni_i2c_gpi function
- memset tx_multi_xfer to 0.
- Removed passing current msg index to geni_i2c_gpi.
- Fixed kernel test robot reported compilation issues.
drivers/i2c/busses/i2c-qcom-geni.c | 203 +++++++++++++++++++++++++----
1 file changed, 178 insertions(+), 25 deletions(-)
diff --git a/drivers/i2c/busses/i2c-qcom-geni.c b/drivers/i2c/busses/i2c-qcom-geni.c
index 7a22e1f46e60..04a7d926dadc 100644
--- a/drivers/i2c/busses/i2c-qcom-geni.c
+++ b/drivers/i2c/busses/i2c-qcom-geni.c
@@ -100,6 +100,10 @@ struct geni_i2c_dev {
struct dma_chan *rx_c;
bool gpi_mode;
bool abort_done;
+ bool is_tx_multi_xfer;
+ u32 num_msgs;
+ u32 tx_irq_cnt;
+ struct gpi_i2c_config *gpi_config;
};
struct geni_i2c_desc {
@@ -500,6 +504,7 @@ static int geni_i2c_tx_one_msg(struct geni_i2c_dev *gi2c, struct i2c_msg *msg,
static void i2c_gpi_cb_result(void *cb, const struct dmaengine_result *result)
{
struct geni_i2c_dev *gi2c = cb;
+ struct gpi_multi_xfer *tx_multi_xfer;
if (result->result != DMA_TRANS_NOERROR) {
dev_err(gi2c->se.dev, "DMA txn failed:%d\n", result->result);
@@ -508,7 +513,21 @@ static void i2c_gpi_cb_result(void *cb, const struct dmaengine_result *result)
dev_dbg(gi2c->se.dev, "DMA xfer has pending: %d\n", result->residue);
}
- complete(&gi2c->done);
+ if (gi2c->is_tx_multi_xfer) {
+ tx_multi_xfer = &gi2c->gpi_config->multi_xfer;
+
+ /*
+ * Send Completion for last message or multiple of NUM_MSGS_PER_IRQ.
+ */
+ if ((tx_multi_xfer->irq_msg_cnt == gi2c->num_msgs - 1) ||
+ (!((tx_multi_xfer->irq_msg_cnt + 1) % NUM_MSGS_PER_IRQ))) {
+ tx_multi_xfer->irq_cnt++;
+ complete(&gi2c->done);
+ }
+ tx_multi_xfer->irq_msg_cnt++;
+ } else {
+ complete(&gi2c->done);
+ }
}
static void geni_i2c_gpi_unmap(struct geni_i2c_dev *gi2c, struct i2c_msg *msg,
@@ -526,7 +545,42 @@ static void geni_i2c_gpi_unmap(struct geni_i2c_dev *gi2c, struct i2c_msg *msg,
}
}
-static int geni_i2c_gpi(struct geni_i2c_dev *gi2c, struct i2c_msg *msg,
+/**
+ * gpi_i2c_multi_desc_unmap() - unmaps the buffers post multi message TX transfers
+ * @dev: pointer to the corresponding dev node
+ * @gi2c: i2c dev handle
+ * @msgs: i2c messages array
+ * @peripheral: pointer to the gpi_i2c_config
+ */
+static void gpi_i2c_multi_desc_unmap(struct geni_i2c_dev *gi2c, struct i2c_msg msgs[],
+ struct gpi_i2c_config *peripheral)
+{
+ u32 msg_xfer_cnt, wr_idx = 0;
+ struct gpi_multi_xfer *tx_multi_xfer = &peripheral->multi_xfer;
+
+ /*
+ * In error case, need to unmap all messages based on the msg_idx_cnt.
+ * Non-error case unmap all the processed messages.
+ */
+ if (gi2c->err)
+ msg_xfer_cnt = tx_multi_xfer->msg_idx_cnt;
+ else
+ msg_xfer_cnt = tx_multi_xfer->irq_cnt * NUM_MSGS_PER_IRQ;
+
+ /* Unmap the processed DMA buffers based on the received interrupt count */
+ for (; tx_multi_xfer->unmap_msg_cnt < msg_xfer_cnt; tx_multi_xfer->unmap_msg_cnt++) {
+ if (tx_multi_xfer->unmap_msg_cnt == gi2c->num_msgs)
+ break;
+ wr_idx = tx_multi_xfer->unmap_msg_cnt % QCOM_GPI_MAX_NUM_MSGS;
+ geni_i2c_gpi_unmap(gi2c, &msgs[tx_multi_xfer->unmap_msg_cnt],
+ tx_multi_xfer->dma_buf[wr_idx],
+ tx_multi_xfer->dma_addr[wr_idx],
+ NULL, (dma_addr_t)NULL);
+ tx_multi_xfer->freed_msg_cnt++;
+ }
+}
+
+static int geni_i2c_gpi(struct geni_i2c_dev *gi2c, struct i2c_msg msgs[],
struct dma_slave_config *config, dma_addr_t *dma_addr_p,
void **buf, unsigned int op, struct dma_chan *dma_chan)
{
@@ -538,26 +592,48 @@ static int geni_i2c_gpi(struct geni_i2c_dev *gi2c, struct i2c_msg *msg,
enum dma_transfer_direction dma_dirn;
struct dma_async_tx_descriptor *desc;
int ret;
+ struct gpi_multi_xfer *gi2c_gpi_xfer;
+ dma_cookie_t cookie;
+ u32 msg_idx;
peripheral = config->peripheral_config;
-
- dma_buf = i2c_get_dma_safe_msg_buf(msg, 1);
- if (!dma_buf)
- return -ENOMEM;
+ gi2c_gpi_xfer = &peripheral->multi_xfer;
+ dma_buf = gi2c_gpi_xfer->dma_buf[gi2c_gpi_xfer->buf_idx];
+ addr = gi2c_gpi_xfer->dma_addr[gi2c_gpi_xfer->buf_idx];
+ msg_idx = gi2c_gpi_xfer->msg_idx_cnt;
+
+ dma_buf = i2c_get_dma_safe_msg_buf(&msgs[msg_idx], 1);
+ if (!dma_buf) {
+ ret = -ENOMEM;
+ goto out;
+ }
if (op == I2C_WRITE)
map_dirn = DMA_TO_DEVICE;
else
map_dirn = DMA_FROM_DEVICE;
- addr = dma_map_single(gi2c->se.dev->parent, dma_buf, msg->len, map_dirn);
+ addr = dma_map_single(gi2c->se.dev->parent, dma_buf,
+ msgs[msg_idx].len, map_dirn);
if (dma_mapping_error(gi2c->se.dev->parent, addr)) {
- i2c_put_dma_safe_msg_buf(dma_buf, msg, false);
- return -ENOMEM;
+ i2c_put_dma_safe_msg_buf(dma_buf, &msgs[msg_idx], false);
+ ret = -ENOMEM;
+ goto out;
+ }
+
+ if (gi2c->is_tx_multi_xfer) {
+ if (((msg_idx + 1) % NUM_MSGS_PER_IRQ))
+ peripheral->flags |= QCOM_GPI_BLOCK_EVENT_IRQ;
+ else
+ peripheral->flags &= ~QCOM_GPI_BLOCK_EVENT_IRQ;
+
+ /* BEI bit to be cleared for last TRE */
+ if (msg_idx == gi2c->num_msgs - 1)
+ peripheral->flags &= ~QCOM_GPI_BLOCK_EVENT_IRQ;
}
/* set the length as message for rx txn */
- peripheral->rx_len = msg->len;
+ peripheral->rx_len = msgs[msg_idx].len;
peripheral->op = op;
ret = dmaengine_slave_config(dma_chan, config);
@@ -575,7 +651,8 @@ static int geni_i2c_gpi(struct geni_i2c_dev *gi2c, struct i2c_msg *msg,
else
dma_dirn = DMA_DEV_TO_MEM;
- desc = dmaengine_prep_slave_single(dma_chan, addr, msg->len, dma_dirn, flags);
+ desc = dmaengine_prep_slave_single(dma_chan, addr, msgs[msg_idx].len,
+ dma_dirn, flags);
if (!desc) {
dev_err(gi2c->se.dev, "prep_slave_sg failed\n");
ret = -EIO;
@@ -585,15 +662,48 @@ static int geni_i2c_gpi(struct geni_i2c_dev *gi2c, struct i2c_msg *msg,
desc->callback_result = i2c_gpi_cb_result;
desc->callback_param = gi2c;
- dmaengine_submit(desc);
- *buf = dma_buf;
- *dma_addr_p = addr;
+ if (!((msgs[msg_idx].flags & I2C_M_RD) && op == I2C_WRITE)) {
+ gi2c_gpi_xfer->msg_idx_cnt++;
+ gi2c_gpi_xfer->buf_idx = (msg_idx + 1) % QCOM_GPI_MAX_NUM_MSGS;
+ }
+ cookie = dmaengine_submit(desc);
+ if (dma_submit_error(cookie)) {
+ dev_err(gi2c->se.dev,
+ "%s: dmaengine_submit failed (%d)\n", __func__, cookie);
+ ret = -EINVAL;
+ goto err_config;
+ }
+ if (gi2c->is_tx_multi_xfer) {
+ dma_async_issue_pending(gi2c->tx_c);
+ if ((msg_idx == (gi2c->num_msgs - 1)) ||
+ (gi2c_gpi_xfer->msg_idx_cnt >=
+ QCOM_GPI_MAX_NUM_MSGS + gi2c_gpi_xfer->freed_msg_cnt)) {
+ ret = gpi_multi_desc_process(gi2c->se.dev, gi2c_gpi_xfer,
+ gi2c->num_msgs, XFER_TIMEOUT,
+ &gi2c->done);
+ if (ret) {
+ dev_err(gi2c->se.dev,
+ "I2C multi write msg transfer timeout: %d\n",
+ ret);
+ gi2c->err = ret;
+ goto err_config;
+ }
+ }
+ } else {
+ /* Non multi descriptor message transfer */
+ *buf = dma_buf;
+ *dma_addr_p = addr;
+ }
return 0;
err_config:
- dma_unmap_single(gi2c->se.dev->parent, addr, msg->len, map_dirn);
- i2c_put_dma_safe_msg_buf(dma_buf, msg, false);
+ dma_unmap_single(gi2c->se.dev->parent, addr,
+ msgs[msg_idx].len, map_dirn);
+ i2c_put_dma_safe_msg_buf(dma_buf, &msgs[msg_idx], false);
+
+out:
+ gi2c->err = ret;
return ret;
}
@@ -605,6 +715,7 @@ static int geni_i2c_gpi_xfer(struct geni_i2c_dev *gi2c, struct i2c_msg msgs[], i
unsigned long time_left;
dma_addr_t tx_addr, rx_addr;
void *tx_buf = NULL, *rx_buf = NULL;
+ struct gpi_multi_xfer *tx_multi_xfer;
const struct geni_i2c_clk_fld *itr = gi2c->clk_fld;
config.peripheral_config = &peripheral;
@@ -618,6 +729,34 @@ static int geni_i2c_gpi_xfer(struct geni_i2c_dev *gi2c, struct i2c_msg msgs[], i
peripheral.set_config = 1;
peripheral.multi_msg = false;
+ gi2c->gpi_config = &peripheral;
+ gi2c->num_msgs = num;
+ gi2c->is_tx_multi_xfer = false;
+ gi2c->tx_irq_cnt = 0;
+
+ tx_multi_xfer = &peripheral.multi_xfer;
+ memset(tx_multi_xfer, 0, sizeof(struct gpi_multi_xfer));
+
+ /*
+ * If number of write messages are four and higher then
+ * configure hardware for multi descriptor transfers with BEI.
+ */
+ if (num >= MIN_NUM_OF_MSGS_MULTI_DESC) {
+ gi2c->is_tx_multi_xfer = true;
+ for (i = 0; i < num; i++) {
+ if (msgs[i].flags & I2C_M_RD) {
+ /*
+ * Multi descriptor transfer with BEI
+ * support is enabled for write transfers.
+ * Add BEI optimization support for read
+ * transfers later.
+ */
+ gi2c->is_tx_multi_xfer = false;
+ break;
+ }
+ }
+ }
+
for (i = 0; i < num; i++) {
gi2c->cur = &msgs[i];
gi2c->err = 0;
@@ -628,14 +767,16 @@ static int geni_i2c_gpi_xfer(struct geni_i2c_dev *gi2c, struct i2c_msg msgs[], i
peripheral.stretch = 1;
peripheral.addr = msgs[i].addr;
+ if (i > 0 && (!(msgs[i].flags & I2C_M_RD)))
+ peripheral.multi_msg = false;
- ret = geni_i2c_gpi(gi2c, &msgs[i], &config,
+ ret = geni_i2c_gpi(gi2c, msgs, &config,
&tx_addr, &tx_buf, I2C_WRITE, gi2c->tx_c);
if (ret)
goto err;
if (msgs[i].flags & I2C_M_RD) {
- ret = geni_i2c_gpi(gi2c, &msgs[i], &config,
+ ret = geni_i2c_gpi(gi2c, msgs, &config,
&rx_addr, &rx_buf, I2C_READ, gi2c->rx_c);
if (ret)
goto err;
@@ -643,18 +784,26 @@ static int geni_i2c_gpi_xfer(struct geni_i2c_dev *gi2c, struct i2c_msg msgs[], i
dma_async_issue_pending(gi2c->rx_c);
}
- dma_async_issue_pending(gi2c->tx_c);
-
- time_left = wait_for_completion_timeout(&gi2c->done, XFER_TIMEOUT);
- if (!time_left)
- gi2c->err = -ETIMEDOUT;
+ if (!gi2c->is_tx_multi_xfer) {
+ dma_async_issue_pending(gi2c->tx_c);
+ time_left = wait_for_completion_timeout(&gi2c->done, XFER_TIMEOUT);
+ if (!time_left) {
+ dev_err(gi2c->se.dev, "%s:I2C timeout\n", __func__);
+ gi2c->err = -ETIMEDOUT;
+ }
+ }
if (gi2c->err) {
ret = gi2c->err;
goto err;
}
- geni_i2c_gpi_unmap(gi2c, &msgs[i], tx_buf, tx_addr, rx_buf, rx_addr);
+ if (!gi2c->is_tx_multi_xfer) {
+ geni_i2c_gpi_unmap(gi2c, &msgs[i], tx_buf, tx_addr, rx_buf, rx_addr);
+ } else if (gi2c->tx_irq_cnt != tx_multi_xfer->irq_cnt) {
+ gi2c->tx_irq_cnt = tx_multi_xfer->irq_cnt;
+ gpi_i2c_multi_desc_unmap(gi2c, msgs, &peripheral);
+ }
}
return num;
@@ -663,7 +812,11 @@ static int geni_i2c_gpi_xfer(struct geni_i2c_dev *gi2c, struct i2c_msg msgs[], i
dev_err(gi2c->se.dev, "GPI transfer failed: %d\n", ret);
dmaengine_terminate_sync(gi2c->rx_c);
dmaengine_terminate_sync(gi2c->tx_c);
- geni_i2c_gpi_unmap(gi2c, &msgs[i], tx_buf, tx_addr, rx_buf, rx_addr);
+ if (gi2c->is_tx_multi_xfer)
+ gpi_i2c_multi_desc_unmap(gi2c, msgs, &peripheral);
+ else
+ geni_i2c_gpi_unmap(gi2c, &msgs[i], tx_buf, tx_addr, rx_buf, rx_addr);
+
return ret;
}
--
2.17.1On Mon, Nov 11, 2024 at 07:32:44PM +0530, Jyothi Kumar Seerapu wrote:
> The I2C driver gets an interrupt upon transfer completion.
> For multiple messages in a single transfer, N interrupts will be
> received for N messages, leading to significant software interrupt
> latency. To mitigate this latency, utilize Block Event Interrupt (BEI)
Please rewrite this to the tone that the reader doesn't know what Block
Event Interrupt is, or that it exists.
> only when an interrupt is necessary. This means large transfers can be
> split into multiple chunks of 8 messages internally, without expecting
> interrupts for the first 7 message completions, only the last one will
> trigger an interrupt indicating 8 messages completed.
>
> By implementing BEI, multi-message transfers can be divided into
> chunks of 8 messages, improving overall transfer time.
You already wrote this in the paragraph above.
Where is this number 8 coming from btw?
> This optimization reduces transfer time from 168 ms to 48 ms for a
> series of 200 I2C write messages in a single transfer, with a
> clock frequency support of 100 kHz.
>
> BEI optimizations are currently implemented for I2C write transfers only,
> as there is no use case for multiple I2C read messages in a single transfer
> at this time.
>
> Signed-off-by: Jyothi Kumar Seerapu <quic_jseerapu@quicinc.com>
> ---
>
> v1 -> v2:
> - Moved gi2c_gpi_xfer->msg_idx_cnt to separate local variable.
> - Updated goto labels for error scenarios in geni_i2c_gpi function
> - memset tx_multi_xfer to 0.
> - Removed passing current msg index to geni_i2c_gpi.
> - Fixed kernel test robot reported compilation issues.
>
> drivers/i2c/busses/i2c-qcom-geni.c | 203 +++++++++++++++++++++++++----
> 1 file changed, 178 insertions(+), 25 deletions(-)
>
> diff --git a/drivers/i2c/busses/i2c-qcom-geni.c b/drivers/i2c/busses/i2c-qcom-geni.c
> index 7a22e1f46e60..04a7d926dadc 100644
> --- a/drivers/i2c/busses/i2c-qcom-geni.c
> +++ b/drivers/i2c/busses/i2c-qcom-geni.c
> @@ -100,6 +100,10 @@ struct geni_i2c_dev {
> struct dma_chan *rx_c;
> bool gpi_mode;
> bool abort_done;
> + bool is_tx_multi_xfer;
> + u32 num_msgs;
> + u32 tx_irq_cnt;
> + struct gpi_i2c_config *gpi_config;
> };
>
> struct geni_i2c_desc {
> @@ -500,6 +504,7 @@ static int geni_i2c_tx_one_msg(struct geni_i2c_dev *gi2c, struct i2c_msg *msg,
> static void i2c_gpi_cb_result(void *cb, const struct dmaengine_result *result)
> {
> struct geni_i2c_dev *gi2c = cb;
> + struct gpi_multi_xfer *tx_multi_xfer;
>
> if (result->result != DMA_TRANS_NOERROR) {
> dev_err(gi2c->se.dev, "DMA txn failed:%d\n", result->result);
> @@ -508,7 +513,21 @@ static void i2c_gpi_cb_result(void *cb, const struct dmaengine_result *result)
> dev_dbg(gi2c->se.dev, "DMA xfer has pending: %d\n", result->residue);
> }
>
> - complete(&gi2c->done);
> + if (gi2c->is_tx_multi_xfer) {
Wouldn't it be cleaner to treat the !is_tx_multi_xfer case as a
multi-xfer of length 1?
> + tx_multi_xfer = &gi2c->gpi_config->multi_xfer;
> +
> + /*
> + * Send Completion for last message or multiple of NUM_MSGS_PER_IRQ.
> + */
> + if ((tx_multi_xfer->irq_msg_cnt == gi2c->num_msgs - 1) ||
> + (!((tx_multi_xfer->irq_msg_cnt + 1) % NUM_MSGS_PER_IRQ))) {
> + tx_multi_xfer->irq_cnt++;
> + complete(&gi2c->done);
Why? You're removing the wait_for_completion_timeout() from
geni_i2c_gpi_xfer() when is_tx_multi_xfer is set.
> + }
> + tx_multi_xfer->irq_msg_cnt++;
> + } else {
> + complete(&gi2c->done);
> + }
> }
>
> static void geni_i2c_gpi_unmap(struct geni_i2c_dev *gi2c, struct i2c_msg *msg,
> @@ -526,7 +545,42 @@ static void geni_i2c_gpi_unmap(struct geni_i2c_dev *gi2c, struct i2c_msg *msg,
> }
> }
>
> -static int geni_i2c_gpi(struct geni_i2c_dev *gi2c, struct i2c_msg *msg,
> +/**
> + * gpi_i2c_multi_desc_unmap() - unmaps the buffers post multi message TX transfers
> + * @dev: pointer to the corresponding dev node
> + * @gi2c: i2c dev handle
> + * @msgs: i2c messages array
> + * @peripheral: pointer to the gpi_i2c_config
> + */
> +static void gpi_i2c_multi_desc_unmap(struct geni_i2c_dev *gi2c, struct i2c_msg msgs[],
> + struct gpi_i2c_config *peripheral)
> +{
> + u32 msg_xfer_cnt, wr_idx = 0;
> + struct gpi_multi_xfer *tx_multi_xfer = &peripheral->multi_xfer;
> +
> + /*
> + * In error case, need to unmap all messages based on the msg_idx_cnt.
> + * Non-error case unmap all the processed messages.
What is the benefit of this optimization, compared to keeping things
simple and just unmap all buffers at the end of geni_i2c_gpi_xfer()?
> + */
> + if (gi2c->err)
> + msg_xfer_cnt = tx_multi_xfer->msg_idx_cnt;
> + else
> + msg_xfer_cnt = tx_multi_xfer->irq_cnt * NUM_MSGS_PER_IRQ;
> +
> + /* Unmap the processed DMA buffers based on the received interrupt count */
> + for (; tx_multi_xfer->unmap_msg_cnt < msg_xfer_cnt; tx_multi_xfer->unmap_msg_cnt++) {
> + if (tx_multi_xfer->unmap_msg_cnt == gi2c->num_msgs)
> + break;
> + wr_idx = tx_multi_xfer->unmap_msg_cnt % QCOM_GPI_MAX_NUM_MSGS;
> + geni_i2c_gpi_unmap(gi2c, &msgs[tx_multi_xfer->unmap_msg_cnt],
> + tx_multi_xfer->dma_buf[wr_idx],
> + tx_multi_xfer->dma_addr[wr_idx],
> + NULL, (dma_addr_t)NULL);
> + tx_multi_xfer->freed_msg_cnt++;
> + }
> +}
> +
> +static int geni_i2c_gpi(struct geni_i2c_dev *gi2c, struct i2c_msg msgs[],
> struct dma_slave_config *config, dma_addr_t *dma_addr_p,
> void **buf, unsigned int op, struct dma_chan *dma_chan)
> {
> @@ -538,26 +592,48 @@ static int geni_i2c_gpi(struct geni_i2c_dev *gi2c, struct i2c_msg *msg,
> enum dma_transfer_direction dma_dirn;
> struct dma_async_tx_descriptor *desc;
> int ret;
> + struct gpi_multi_xfer *gi2c_gpi_xfer;
> + dma_cookie_t cookie;
> + u32 msg_idx;
>
> peripheral = config->peripheral_config;
> -
> - dma_buf = i2c_get_dma_safe_msg_buf(msg, 1);
> - if (!dma_buf)
> - return -ENOMEM;
> + gi2c_gpi_xfer = &peripheral->multi_xfer;
> + dma_buf = gi2c_gpi_xfer->dma_buf[gi2c_gpi_xfer->buf_idx];
> + addr = gi2c_gpi_xfer->dma_addr[gi2c_gpi_xfer->buf_idx];
> + msg_idx = gi2c_gpi_xfer->msg_idx_cnt;
> +
> + dma_buf = i2c_get_dma_safe_msg_buf(&msgs[msg_idx], 1);
> + if (!dma_buf) {
> + ret = -ENOMEM;
> + goto out;
> + }
>
> if (op == I2C_WRITE)
> map_dirn = DMA_TO_DEVICE;
> else
> map_dirn = DMA_FROM_DEVICE;
>
> - addr = dma_map_single(gi2c->se.dev->parent, dma_buf, msg->len, map_dirn);
> + addr = dma_map_single(gi2c->se.dev->parent, dma_buf,
> + msgs[msg_idx].len, map_dirn);
> if (dma_mapping_error(gi2c->se.dev->parent, addr)) {
> - i2c_put_dma_safe_msg_buf(dma_buf, msg, false);
> - return -ENOMEM;
> + i2c_put_dma_safe_msg_buf(dma_buf, &msgs[msg_idx], false);
> + ret = -ENOMEM;
> + goto out;
> + }
> +
> + if (gi2c->is_tx_multi_xfer) {
> + if (((msg_idx + 1) % NUM_MSGS_PER_IRQ))
> + peripheral->flags |= QCOM_GPI_BLOCK_EVENT_IRQ;
> + else
> + peripheral->flags &= ~QCOM_GPI_BLOCK_EVENT_IRQ;
> +
> + /* BEI bit to be cleared for last TRE */
> + if (msg_idx == gi2c->num_msgs - 1)
> + peripheral->flags &= ~QCOM_GPI_BLOCK_EVENT_IRQ;
> }
>
> /* set the length as message for rx txn */
> - peripheral->rx_len = msg->len;
> + peripheral->rx_len = msgs[msg_idx].len;
> peripheral->op = op;
>
> ret = dmaengine_slave_config(dma_chan, config);
> @@ -575,7 +651,8 @@ static int geni_i2c_gpi(struct geni_i2c_dev *gi2c, struct i2c_msg *msg,
> else
> dma_dirn = DMA_DEV_TO_MEM;
>
> - desc = dmaengine_prep_slave_single(dma_chan, addr, msg->len, dma_dirn, flags);
> + desc = dmaengine_prep_slave_single(dma_chan, addr, msgs[msg_idx].len,
> + dma_dirn, flags);
> if (!desc) {
> dev_err(gi2c->se.dev, "prep_slave_sg failed\n");
> ret = -EIO;
> @@ -585,15 +662,48 @@ static int geni_i2c_gpi(struct geni_i2c_dev *gi2c, struct i2c_msg *msg,
> desc->callback_result = i2c_gpi_cb_result;
> desc->callback_param = gi2c;
>
> - dmaengine_submit(desc);
> - *buf = dma_buf;
> - *dma_addr_p = addr;
> + if (!((msgs[msg_idx].flags & I2C_M_RD) && op == I2C_WRITE)) {
> + gi2c_gpi_xfer->msg_idx_cnt++;
> + gi2c_gpi_xfer->buf_idx = (msg_idx + 1) % QCOM_GPI_MAX_NUM_MSGS;
> + }
> + cookie = dmaengine_submit(desc);
> + if (dma_submit_error(cookie)) {
> + dev_err(gi2c->se.dev,
> + "%s: dmaengine_submit failed (%d)\n", __func__, cookie);
> + ret = -EINVAL;
> + goto err_config;
> + }
>
> + if (gi2c->is_tx_multi_xfer) {
> + dma_async_issue_pending(gi2c->tx_c);
> + if ((msg_idx == (gi2c->num_msgs - 1)) ||
> + (gi2c_gpi_xfer->msg_idx_cnt >=
> + QCOM_GPI_MAX_NUM_MSGS + gi2c_gpi_xfer->freed_msg_cnt)) {
> + ret = gpi_multi_desc_process(gi2c->se.dev, gi2c_gpi_xfer,
A function call straight into the GPI driver? I'm not entirely familiar
with the details of the dmaengine API, but this doesn't look correct.
> + gi2c->num_msgs, XFER_TIMEOUT,
> + &gi2c->done);
> + if (ret) {
> + dev_err(gi2c->se.dev,
> + "I2C multi write msg transfer timeout: %d\n",
> + ret);
> + gi2c->err = ret;
> + goto err_config;
> + }
> + }
> + } else {
> + /* Non multi descriptor message transfer */
> + *buf = dma_buf;
> + *dma_addr_p = addr;
> + }
> return 0;
>
> err_config:
> - dma_unmap_single(gi2c->se.dev->parent, addr, msg->len, map_dirn);
> - i2c_put_dma_safe_msg_buf(dma_buf, msg, false);
> + dma_unmap_single(gi2c->se.dev->parent, addr,
> + msgs[msg_idx].len, map_dirn);
> + i2c_put_dma_safe_msg_buf(dma_buf, &msgs[msg_idx], false);
> +
> +out:
> + gi2c->err = ret;
> return ret;
> }
>
> @@ -605,6 +715,7 @@ static int geni_i2c_gpi_xfer(struct geni_i2c_dev *gi2c, struct i2c_msg msgs[], i
> unsigned long time_left;
> dma_addr_t tx_addr, rx_addr;
> void *tx_buf = NULL, *rx_buf = NULL;
> + struct gpi_multi_xfer *tx_multi_xfer;
> const struct geni_i2c_clk_fld *itr = gi2c->clk_fld;
>
> config.peripheral_config = &peripheral;
> @@ -618,6 +729,34 @@ static int geni_i2c_gpi_xfer(struct geni_i2c_dev *gi2c, struct i2c_msg msgs[], i
> peripheral.set_config = 1;
> peripheral.multi_msg = false;
>
> + gi2c->gpi_config = &peripheral;
> + gi2c->num_msgs = num;
> + gi2c->is_tx_multi_xfer = false;
> + gi2c->tx_irq_cnt = 0;
> +
> + tx_multi_xfer = &peripheral.multi_xfer;
> + memset(tx_multi_xfer, 0, sizeof(struct gpi_multi_xfer));
> +
> + /*
> + * If number of write messages are four and higher then
Why four?
> + * configure hardware for multi descriptor transfers with BEI.
> + */
> + if (num >= MIN_NUM_OF_MSGS_MULTI_DESC) {
> + gi2c->is_tx_multi_xfer = true;
> + for (i = 0; i < num; i++) {
> + if (msgs[i].flags & I2C_M_RD) {
> + /*
> + * Multi descriptor transfer with BEI
> + * support is enabled for write transfers.
> + * Add BEI optimization support for read
> + * transfers later.
Prefix this comment with "TODO:"
> + */
> + gi2c->is_tx_multi_xfer = false;
> + break;
> + }
> + }
> + }
> +
> for (i = 0; i < num; i++) {
> gi2c->cur = &msgs[i];
> gi2c->err = 0;
> @@ -628,14 +767,16 @@ static int geni_i2c_gpi_xfer(struct geni_i2c_dev *gi2c, struct i2c_msg msgs[], i
> peripheral.stretch = 1;
>
> peripheral.addr = msgs[i].addr;
> + if (i > 0 && (!(msgs[i].flags & I2C_M_RD)))
> + peripheral.multi_msg = false;
>
> - ret = geni_i2c_gpi(gi2c, &msgs[i], &config,
> + ret = geni_i2c_gpi(gi2c, msgs, &config,
> &tx_addr, &tx_buf, I2C_WRITE, gi2c->tx_c);
> if (ret)
> goto err;
>
> if (msgs[i].flags & I2C_M_RD) {
> - ret = geni_i2c_gpi(gi2c, &msgs[i], &config,
> + ret = geni_i2c_gpi(gi2c, msgs, &config,
> &rx_addr, &rx_buf, I2C_READ, gi2c->rx_c);
> if (ret)
> goto err;
> @@ -643,18 +784,26 @@ static int geni_i2c_gpi_xfer(struct geni_i2c_dev *gi2c, struct i2c_msg msgs[], i
> dma_async_issue_pending(gi2c->rx_c);
> }
>
> - dma_async_issue_pending(gi2c->tx_c);
> -
> - time_left = wait_for_completion_timeout(&gi2c->done, XFER_TIMEOUT);
> - if (!time_left)
> - gi2c->err = -ETIMEDOUT;
> + if (!gi2c->is_tx_multi_xfer) {
> + dma_async_issue_pending(gi2c->tx_c);
> + time_left = wait_for_completion_timeout(&gi2c->done, XFER_TIMEOUT);
By making this conditional on !is_tx_multi_xfer transfers, what makes
the loop wait for the transfer to complete before you below unmap the
buffers?
> + if (!time_left) {
> + dev_err(gi2c->se.dev, "%s:I2C timeout\n", __func__);
> + gi2c->err = -ETIMEDOUT;
> + }
> + }
>
> if (gi2c->err) {
> ret = gi2c->err;
> goto err;
> }
>
> - geni_i2c_gpi_unmap(gi2c, &msgs[i], tx_buf, tx_addr, rx_buf, rx_addr);
> + if (!gi2c->is_tx_multi_xfer) {
> + geni_i2c_gpi_unmap(gi2c, &msgs[i], tx_buf, tx_addr, rx_buf, rx_addr);
> + } else if (gi2c->tx_irq_cnt != tx_multi_xfer->irq_cnt) {
> + gi2c->tx_irq_cnt = tx_multi_xfer->irq_cnt;
> + gpi_i2c_multi_desc_unmap(gi2c, msgs, &peripheral);
> + }
> }
>
> return num;
> @@ -663,7 +812,11 @@ static int geni_i2c_gpi_xfer(struct geni_i2c_dev *gi2c, struct i2c_msg msgs[], i
> dev_err(gi2c->se.dev, "GPI transfer failed: %d\n", ret);
> dmaengine_terminate_sync(gi2c->rx_c);
> dmaengine_terminate_sync(gi2c->tx_c);
> - geni_i2c_gpi_unmap(gi2c, &msgs[i], tx_buf, tx_addr, rx_buf, rx_addr);
> + if (gi2c->is_tx_multi_xfer)
> + gpi_i2c_multi_desc_unmap(gi2c, msgs, &peripheral);
> + else
> + geni_i2c_gpi_unmap(gi2c, &msgs[i], tx_buf, tx_addr, rx_buf, rx_addr);
> +
As above, it would be nice if multi-xfer was just a special case with a
single buffer; rather than inflating the cyclomatic complexity.
Regards,
Bjorn
> return ret;
> }
>
> --
> 2.17.1
>
>
On 11/12/2024 10:03 AM, Bjorn Andersson wrote:
> On Mon, Nov 11, 2024 at 07:32:44PM +0530, Jyothi Kumar Seerapu wrote:
>> The I2C driver gets an interrupt upon transfer completion.
>> For multiple messages in a single transfer, N interrupts will be
>> received for N messages, leading to significant software interrupt
>> latency. To mitigate this latency, utilize Block Event Interrupt (BEI)
>
> Please rewrite this to the tone that the reader doesn't know what Block
> Event Interrupt is, or that it exists.
Sure, done.
>
>> only when an interrupt is necessary. This means large transfers can be
>> split into multiple chunks of 8 messages internally, without expecting
>> interrupts for the first 7 message completions, only the last one will
>> trigger an interrupt indicating 8 messages completed.
>>
>> By implementing BEI, multi-message transfers can be divided into
>> chunks of 8 messages, improving overall transfer time.
>
> You already wrote this in the paragraph above.
yeah removed it.
>
>
> Where is this number 8 coming from btw?
Its documented in "qcom-gpi-dma.h" file.
Trigger an interrupt, after the completion of 8 messages.
>
>> This optimization reduces transfer time from 168 ms to 48 ms for a
>> series of 200 I2C write messages in a single transfer, with a
>> clock frequency support of 100 kHz.
>>
>> BEI optimizations are currently implemented for I2C write transfers only,
>> as there is no use case for multiple I2C read messages in a single transfer
>> at this time.
>>
>> Signed-off-by: Jyothi Kumar Seerapu <quic_jseerapu@quicinc.com>
>> ---
>>
>> v1 -> v2:
>> - Moved gi2c_gpi_xfer->msg_idx_cnt to separate local variable.
>> - Updated goto labels for error scenarios in geni_i2c_gpi function
>> - memset tx_multi_xfer to 0.
>> - Removed passing current msg index to geni_i2c_gpi.
>> - Fixed kernel test robot reported compilation issues.
>>
>> drivers/i2c/busses/i2c-qcom-geni.c | 203 +++++++++++++++++++++++++----
>> 1 file changed, 178 insertions(+), 25 deletions(-)
>>
>> diff --git a/drivers/i2c/busses/i2c-qcom-geni.c b/drivers/i2c/busses/i2c-qcom-geni.c
>> index 7a22e1f46e60..04a7d926dadc 100644
>> --- a/drivers/i2c/busses/i2c-qcom-geni.c
>> +++ b/drivers/i2c/busses/i2c-qcom-geni.c
>> @@ -100,6 +100,10 @@ struct geni_i2c_dev {
>> struct dma_chan *rx_c;
>> bool gpi_mode;
>> bool abort_done;
>> + bool is_tx_multi_xfer;
>> + u32 num_msgs;
>> + u32 tx_irq_cnt;
>> + struct gpi_i2c_config *gpi_config;
>> };
>>
>> struct geni_i2c_desc {
>> @@ -500,6 +504,7 @@ static int geni_i2c_tx_one_msg(struct geni_i2c_dev *gi2c, struct i2c_msg *msg,
>> static void i2c_gpi_cb_result(void *cb, const struct dmaengine_result *result)
>> {
>> struct geni_i2c_dev *gi2c = cb;
>> + struct gpi_multi_xfer *tx_multi_xfer;
>>
>> if (result->result != DMA_TRANS_NOERROR) {
>> dev_err(gi2c->se.dev, "DMA txn failed:%d\n", result->result);
>> @@ -508,7 +513,21 @@ static void i2c_gpi_cb_result(void *cb, const struct dmaengine_result *result)
>> dev_dbg(gi2c->se.dev, "DMA xfer has pending: %d\n", result->residue);
>> }
>>
>> - complete(&gi2c->done);
>> + if (gi2c->is_tx_multi_xfer) {
>
> Wouldn't it be cleaner to treat the !is_tx_multi_xfer case as a
> multi-xfer of length 1?
Sure, addressed the change in V3 patch.
>
>> + tx_multi_xfer = &gi2c->gpi_config->multi_xfer;
>> +
>> + /*
>> + * Send Completion for last message or multiple of NUM_MSGS_PER_IRQ.
>> + */
>> + if ((tx_multi_xfer->irq_msg_cnt == gi2c->num_msgs - 1) ||
>> + (!((tx_multi_xfer->irq_msg_cnt + 1) % NUM_MSGS_PER_IRQ))) {
>> + tx_multi_xfer->irq_cnt++;
>> + complete(&gi2c->done);
>
> Why? You're removing the wait_for_completion_timeout() from
> geni_i2c_gpi_xfer() when is_tx_multi_xfer is set.
For (!is_tx_multi_xfer) case, need to wait for every message.
But whereas for multi-message (when is_tx_multi_xfer is set) cases,
"wait_for_completion_timeout" will trigger after queuing messages till
QCOM_GPI_MAX_NUM_MSGS (32) or total number of i2c msgs and
"wait_for_completion_timeout" for this case is handled in GPI driver.
>
>> + }
>> + tx_multi_xfer->irq_msg_cnt++;
>> + } else {
>> + complete(&gi2c->done);
>> + }
>> }
>>
>> static void geni_i2c_gpi_unmap(struct geni_i2c_dev *gi2c, struct i2c_msg *msg,
>> @@ -526,7 +545,42 @@ static void geni_i2c_gpi_unmap(struct geni_i2c_dev *gi2c, struct i2c_msg *msg,
>> }
>> }
>>
>> -static int geni_i2c_gpi(struct geni_i2c_dev *gi2c, struct i2c_msg *msg,
>> +/**
>> + * gpi_i2c_multi_desc_unmap() - unmaps the buffers post multi message TX transfers
>> + * @dev: pointer to the corresponding dev node
>> + * @gi2c: i2c dev handle
>> + * @msgs: i2c messages array
>> + * @peripheral: pointer to the gpi_i2c_config
>> + */
>> +static void gpi_i2c_multi_desc_unmap(struct geni_i2c_dev *gi2c, struct i2c_msg msgs[],
>> + struct gpi_i2c_config *peripheral)
>> +{
>> + u32 msg_xfer_cnt, wr_idx = 0;
>> + struct gpi_multi_xfer *tx_multi_xfer = &peripheral->multi_xfer;
>> +
>> + /*
>> + * In error case, need to unmap all messages based on the msg_idx_cnt.
>> + * Non-error case unmap all the processed messages.
>
> What is the benefit of this optimization, compared to keeping things
> simple and just unmap all buffers at the end of geni_i2c_gpi_xfer()?
The maximum number of messages can allocate and submit to GSI hardware
is 16 (QCOM_GPI_MAX_NUM_MSGS) and to handle more messages beyond this
need to unmap the processed messages.
If there is 200 messages or more in a transfer then we need to unmap the
processed messages for handling all messages in a transfer.
So, instead of Unmap all messages together, here unmapping the chunk of
messages.
>
>> + */
>> + if (gi2c->err)
>> + msg_xfer_cnt = tx_multi_xfer->msg_idx_cnt;
>> + else
>> + msg_xfer_cnt = tx_multi_xfer->irq_cnt * NUM_MSGS_PER_IRQ;
>> +
>> + /* Unmap the processed DMA buffers based on the received interrupt count */
>> + for (; tx_multi_xfer->unmap_msg_cnt < msg_xfer_cnt; tx_multi_xfer->unmap_msg_cnt++) {
>> + if (tx_multi_xfer->unmap_msg_cnt == gi2c->num_msgs)
>> + break;
>> + wr_idx = tx_multi_xfer->unmap_msg_cnt % QCOM_GPI_MAX_NUM_MSGS;
>> + geni_i2c_gpi_unmap(gi2c, &msgs[tx_multi_xfer->unmap_msg_cnt],
>> + tx_multi_xfer->dma_buf[wr_idx],
>> + tx_multi_xfer->dma_addr[wr_idx],
>> + NULL, (dma_addr_t)NULL);
>> + tx_multi_xfer->freed_msg_cnt++;
>> + }
>> +}
>> +
>> +static int geni_i2c_gpi(struct geni_i2c_dev *gi2c, struct i2c_msg msgs[],
>> struct dma_slave_config *config, dma_addr_t *dma_addr_p,
>> void **buf, unsigned int op, struct dma_chan *dma_chan)
>> {
>> @@ -538,26 +592,48 @@ static int geni_i2c_gpi(struct geni_i2c_dev *gi2c, struct i2c_msg *msg,
>> enum dma_transfer_direction dma_dirn;
>> struct dma_async_tx_descriptor *desc;
>> int ret;
>> + struct gpi_multi_xfer *gi2c_gpi_xfer;
>> + dma_cookie_t cookie;
>> + u32 msg_idx;
>>
>> peripheral = config->peripheral_config;
>> -
>> - dma_buf = i2c_get_dma_safe_msg_buf(msg, 1);
>> - if (!dma_buf)
>> - return -ENOMEM;
>> + gi2c_gpi_xfer = &peripheral->multi_xfer;
>> + dma_buf = gi2c_gpi_xfer->dma_buf[gi2c_gpi_xfer->buf_idx];
>> + addr = gi2c_gpi_xfer->dma_addr[gi2c_gpi_xfer->buf_idx];
>> + msg_idx = gi2c_gpi_xfer->msg_idx_cnt;
>> +
>> + dma_buf = i2c_get_dma_safe_msg_buf(&msgs[msg_idx], 1);
>> + if (!dma_buf) {
>> + ret = -ENOMEM;
>> + goto out;
>> + }
>>
>> if (op == I2C_WRITE)
>> map_dirn = DMA_TO_DEVICE;
>> else
>> map_dirn = DMA_FROM_DEVICE;
>>
>> - addr = dma_map_single(gi2c->se.dev->parent, dma_buf, msg->len, map_dirn);
>> + addr = dma_map_single(gi2c->se.dev->parent, dma_buf,
>> + msgs[msg_idx].len, map_dirn);
>> if (dma_mapping_error(gi2c->se.dev->parent, addr)) {
>> - i2c_put_dma_safe_msg_buf(dma_buf, msg, false);
>> - return -ENOMEM;
>> + i2c_put_dma_safe_msg_buf(dma_buf, &msgs[msg_idx], false);
>> + ret = -ENOMEM;
>> + goto out;
>> + }
>> +
>> + if (gi2c->is_tx_multi_xfer) {
>> + if (((msg_idx + 1) % NUM_MSGS_PER_IRQ))
>> + peripheral->flags |= QCOM_GPI_BLOCK_EVENT_IRQ;
>> + else
>> + peripheral->flags &= ~QCOM_GPI_BLOCK_EVENT_IRQ;
>> +
>> + /* BEI bit to be cleared for last TRE */
>> + if (msg_idx == gi2c->num_msgs - 1)
>> + peripheral->flags &= ~QCOM_GPI_BLOCK_EVENT_IRQ;
>> }
>>
>> /* set the length as message for rx txn */
>> - peripheral->rx_len = msg->len;
>> + peripheral->rx_len = msgs[msg_idx].len;
>> peripheral->op = op;
>>
>> ret = dmaengine_slave_config(dma_chan, config);
>> @@ -575,7 +651,8 @@ static int geni_i2c_gpi(struct geni_i2c_dev *gi2c, struct i2c_msg *msg,
>> else
>> dma_dirn = DMA_DEV_TO_MEM;
>>
>> - desc = dmaengine_prep_slave_single(dma_chan, addr, msg->len, dma_dirn, flags);
>> + desc = dmaengine_prep_slave_single(dma_chan, addr, msgs[msg_idx].len,
>> + dma_dirn, flags);
>> if (!desc) {
>> dev_err(gi2c->se.dev, "prep_slave_sg failed\n");
>> ret = -EIO;
>> @@ -585,15 +662,48 @@ static int geni_i2c_gpi(struct geni_i2c_dev *gi2c, struct i2c_msg *msg,
>> desc->callback_result = i2c_gpi_cb_result;
>> desc->callback_param = gi2c;
>>
>> - dmaengine_submit(desc);
>> - *buf = dma_buf;
>> - *dma_addr_p = addr;
>> + if (!((msgs[msg_idx].flags & I2C_M_RD) && op == I2C_WRITE)) {
>> + gi2c_gpi_xfer->msg_idx_cnt++;
>> + gi2c_gpi_xfer->buf_idx = (msg_idx + 1) % QCOM_GPI_MAX_NUM_MSGS;
>> + }
>> + cookie = dmaengine_submit(desc);
>> + if (dma_submit_error(cookie)) {
>> + dev_err(gi2c->se.dev,
>> + "%s: dmaengine_submit failed (%d)\n", __func__, cookie);
>> + ret = -EINVAL;
>> + goto err_config;
>> + }
>>
>> + if (gi2c->is_tx_multi_xfer) {
>> + dma_async_issue_pending(gi2c->tx_c);
>> + if ((msg_idx == (gi2c->num_msgs - 1)) ||
>> + (gi2c_gpi_xfer->msg_idx_cnt >=
>> + QCOM_GPI_MAX_NUM_MSGS + gi2c_gpi_xfer->freed_msg_cnt)) {
>> + ret = gpi_multi_desc_process(gi2c->se.dev, gi2c_gpi_xfer,
>
> A function call straight into the GPI driver? I'm not entirely familiar
> with the details of the dmaengine API, but this doesn't look correct.
"gpi_multi_desc_process" can be used for the other protocols as well and
so defined here. Please let me know if its not a good idea to make this
as common function for all required protocols and keep in GPI driver.
Also, gpi_multi_desc_process can't be fit into dmaengine API and so
invoked a function call to GPI driver.
>
>> + gi2c->num_msgs, XFER_TIMEOUT,
>> + &gi2c->done);
>> + if (ret) {
>> + dev_err(gi2c->se.dev,
>> + "I2C multi write msg transfer timeout: %d\n",
>> + ret);
>> + gi2c->err = ret;
>> + goto err_config;
>> + }
>> + }
>> + } else {
>> + /* Non multi descriptor message transfer */
>> + *buf = dma_buf;
>> + *dma_addr_p = addr;
>> + }
>> return 0;
>>
>> err_config:
>> - dma_unmap_single(gi2c->se.dev->parent, addr, msg->len, map_dirn);
>> - i2c_put_dma_safe_msg_buf(dma_buf, msg, false);
>> + dma_unmap_single(gi2c->se.dev->parent, addr,
>> + msgs[msg_idx].len, map_dirn);
>> + i2c_put_dma_safe_msg_buf(dma_buf, &msgs[msg_idx], false);
>> +
>> +out:
>> + gi2c->err = ret;
>> return ret;
>> }
>>
>> @@ -605,6 +715,7 @@ static int geni_i2c_gpi_xfer(struct geni_i2c_dev *gi2c, struct i2c_msg msgs[], i
>> unsigned long time_left;
>> dma_addr_t tx_addr, rx_addr;
>> void *tx_buf = NULL, *rx_buf = NULL;
>> + struct gpi_multi_xfer *tx_multi_xfer;
>> const struct geni_i2c_clk_fld *itr = gi2c->clk_fld;
>>
>> config.peripheral_config = &peripheral;
>> @@ -618,6 +729,34 @@ static int geni_i2c_gpi_xfer(struct geni_i2c_dev *gi2c, struct i2c_msg msgs[], i
>> peripheral.set_config = 1;
>> peripheral.multi_msg = false;
>>
>> + gi2c->gpi_config = &peripheral;
>> + gi2c->num_msgs = num;
>> + gi2c->is_tx_multi_xfer = false;
>> + gi2c->tx_irq_cnt = 0;
>> +
>> + tx_multi_xfer = &peripheral.multi_xfer;
>> + memset(tx_multi_xfer, 0, sizeof(struct gpi_multi_xfer));
>> +
>> + /*
>> + * If number of write messages are four and higher then
>
> Why four?
It changed to 2 in V3, so that if the number of messages in a transfer
are greter than 1, then "is_tx_multi_xfer" is set.
>
>> + * configure hardware for multi descriptor transfers with BEI.
>> + */
>> + if (num >= MIN_NUM_OF_MSGS_MULTI_DESC) {
>> + gi2c->is_tx_multi_xfer = true;
>> + for (i = 0; i < num; i++) {
>> + if (msgs[i].flags & I2C_M_RD) {
>> + /*
>> + * Multi descriptor transfer with BEI
>> + * support is enabled for write transfers.
>> + * Add BEI optimization support for read
>> + * transfers later.
>
> Prefix this comment with "TODO:"
Done
>
>> + */
>> + gi2c->is_tx_multi_xfer = false;
>> + break;
>> + }
>> + }
>> + }
>> +
>> for (i = 0; i < num; i++) {
>> gi2c->cur = &msgs[i];
>> gi2c->err = 0;
>> @@ -628,14 +767,16 @@ static int geni_i2c_gpi_xfer(struct geni_i2c_dev *gi2c, struct i2c_msg msgs[], i
>> peripheral.stretch = 1;
>>
>> peripheral.addr = msgs[i].addr;
>> + if (i > 0 && (!(msgs[i].flags & I2C_M_RD)))
>> + peripheral.multi_msg = false;
>>
>> - ret = geni_i2c_gpi(gi2c, &msgs[i], &config,
>> + ret = geni_i2c_gpi(gi2c, msgs, &config,
>> &tx_addr, &tx_buf, I2C_WRITE, gi2c->tx_c);
>> if (ret)
>> goto err;
>>
>> if (msgs[i].flags & I2C_M_RD) {
>> - ret = geni_i2c_gpi(gi2c, &msgs[i], &config,
>> + ret = geni_i2c_gpi(gi2c, msgs, &config,
>> &rx_addr, &rx_buf, I2C_READ, gi2c->rx_c);
>> if (ret)
>> goto err;
>> @@ -643,18 +784,26 @@ static int geni_i2c_gpi_xfer(struct geni_i2c_dev *gi2c, struct i2c_msg msgs[], i
>> dma_async_issue_pending(gi2c->rx_c);
>> }
>>
>> - dma_async_issue_pending(gi2c->tx_c);
>> -
>> - time_left = wait_for_completion_timeout(&gi2c->done, XFER_TIMEOUT);
>> - if (!time_left)
>> - gi2c->err = -ETIMEDOUT;
>> + if (!gi2c->is_tx_multi_xfer) {
>> + dma_async_issue_pending(gi2c->tx_c);
>> + time_left = wait_for_completion_timeout(&gi2c->done, XFER_TIMEOUT);
>
> By making this conditional on !is_tx_multi_xfer transfers, what makes
> the loop wait for the transfer to complete before you below unmap the
> buffers?
Yes, for (!is_tx_multi_xfer) case, need to wait for every message and
then unmap it and for is_tx_multi_xfer transfers shouldn't unmap per
message wise instead unmap the chunk of messages together.
>
>> + if (!time_left) {
>> + dev_err(gi2c->se.dev, "%s:I2C timeout\n", __func__);
>> + gi2c->err = -ETIMEDOUT;
>> + }
>> + }
>>
>> if (gi2c->err) {
>> ret = gi2c->err;
>> goto err;
>> }
>>
>> - geni_i2c_gpi_unmap(gi2c, &msgs[i], tx_buf, tx_addr, rx_buf, rx_addr);
>> + if (!gi2c->is_tx_multi_xfer) {
>> + geni_i2c_gpi_unmap(gi2c, &msgs[i], tx_buf, tx_addr, rx_buf, rx_addr);
>> + } else if (gi2c->tx_irq_cnt != tx_multi_xfer->irq_cnt) {
>> + gi2c->tx_irq_cnt = tx_multi_xfer->irq_cnt;
>> + gpi_i2c_multi_desc_unmap(gi2c, msgs, &peripheral);
>> + }
>> }
>>
>> return num;
>> @@ -663,7 +812,11 @@ static int geni_i2c_gpi_xfer(struct geni_i2c_dev *gi2c, struct i2c_msg msgs[], i
>> dev_err(gi2c->se.dev, "GPI transfer failed: %d\n", ret);
>> dmaengine_terminate_sync(gi2c->rx_c);
>> dmaengine_terminate_sync(gi2c->tx_c);
>> - geni_i2c_gpi_unmap(gi2c, &msgs[i], tx_buf, tx_addr, rx_buf, rx_addr);
>> + if (gi2c->is_tx_multi_xfer)
>> + gpi_i2c_multi_desc_unmap(gi2c, msgs, &peripheral);
>> + else
>> + geni_i2c_gpi_unmap(gi2c, &msgs[i], tx_buf, tx_addr, rx_buf, rx_addr);
>> +
>
> As above, it would be nice if multi-xfer was just a special case with a
> single buffer; rather than inflating the cyclomatic complexity.
For a single i2c message, data can be placed at contigious memory
locations, but for multiple i2c messages in a transfer, all the messages
offsets and data may not guarantee to placed at contigious memory
locations.
So, looks single large buffer is not helpful here.
>
> Regards,
> Bjorn
>
>> return ret;
>> }
>>
>> --
>> 2.17.1
>>
>>
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