On I2C_SLAVE_WRITE_REQUESTED event, Slave already ACK'ed on the address
phase. But as the backend driver is busy and unable to process any
request from Master, issue RxCmdLast for Slave to auto send NACK on
next incoming byte.

Signed-off-by: Quan Nguyen <quan@os.amperecomputing.com>
---
v10:
  + Issuing RxCmdLast command for all errnos     [Wolfram]

v9:
  + Update commit message and add comment to explain
    the effect of issuing RxCmdLast when Slave busy [Quan]

v7 -> v8:
  + None

v6:
  + New introduced in v6                            [Quan]
---
 drivers/i2c/busses/i2c-aspeed.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/drivers/i2c/busses/i2c-aspeed.c b/drivers/i2c/busses/i2c-aspeed.c
index 185dedfebbac..c64c381b69b7 100644
--- a/drivers/i2c/busses/i2c-aspeed.c
+++ b/drivers/i2c/busses/i2c-aspeed.c
@@ -244,6 +244,7 @@ static u32 aspeed_i2c_slave_irq(struct aspeed_i2c_bus *bus, u32 irq_status)
 	u32 command, irq_handled = 0;
 	struct i2c_client *slave = bus->slave;
 	u8 value;
+	int ret;
 
 	if (!slave)
 		return 0;
@@ -311,7 +312,13 @@ static u32 aspeed_i2c_slave_irq(struct aspeed_i2c_bus *bus, u32 irq_status)
 		break;
 	case ASPEED_I2C_SLAVE_WRITE_REQUESTED:
 		bus->slave_state = ASPEED_I2C_SLAVE_WRITE_RECEIVED;
-		i2c_slave_event(slave, I2C_SLAVE_WRITE_REQUESTED, &value);
+		ret = i2c_slave_event(slave, I2C_SLAVE_WRITE_REQUESTED, &value);
+		/*
+		 * Slave ACK's on this address phase already but as the backend driver
+		 * returns an errno, the bus driver should nack the next incoming byte.
+		 */
+		if (ret < 0)
+			writel(ASPEED_I2CD_M_S_RX_CMD_LAST, bus->base + ASPEED_I2C_CMD_REG);
 		break;
 	case ASPEED_I2C_SLAVE_WRITE_RECEIVED:
 		i2c_slave_event(slave, I2C_SLAVE_WRITE_RECEIVED, &value);
-- 
2.35.1

On Tue, Oct 04, 2022 at 04:31:06PM +0700, Quan Nguyen wrote:
> On I2C_SLAVE_WRITE_REQUESTED event, Slave already ACK'ed on the address
> phase. But as the backend driver is busy and unable to process any
> request from Master, issue RxCmdLast for Slave to auto send NACK on
> next incoming byte.
> 
> Signed-off-by: Quan Nguyen <quan@os.amperecomputing.com>

Applied to for-current, thanks!

Dear Wolfram,

Thank you for your patience with me through many versions.

Best regards,
- Quan


On 06/10/2022 02:06, Wolfram Sang wrote:
> On Tue, Oct 04, 2022 at 04:31:06PM +0700, Quan Nguyen wrote:
>> On I2C_SLAVE_WRITE_REQUESTED event, Slave already ACK'ed on the address
>> phase. But as the backend driver is busy and unable to process any
>> request from Master, issue RxCmdLast for Slave to auto send NACK on
>> next incoming byte.
>>
>> Signed-off-by: Quan Nguyen <quan@os.amperecomputing.com>
> 
> Applied to for-current, thanks!
>

> Thank you for your patience with me through many versions.

You are welcome. In the end, I think the update of the target interface
is an improvement, in deed. So, thank you for that!