i2c: sprd: Modification of UNIOC Platform IIC Driver

[PATCH 3/8] i2c: sprd: Use global variables to record IIC ack/nack status instead of local variables

Posted by Huangzheng Lai 2 years, 4 months ago

We found that when the interrupt bit of the IIC controller is cleared,
the ack/nack bit is also cleared at the same time. After clearing the
interrupt bit in sprd_i2c_isr(), incorrect ack/nack information will be
obtained in sprd_i2c_isr_thread(), resulting in incorrect communication
when nack cannot be recognized. To solve this problem, we used a global
variable to record ack/nack information before clearing the interrupt
bit instead of a local variable.

Signed-off-by: Huangzheng Lai <Huangzheng.Lai@unisoc.com>
---
 drivers/i2c/busses/i2c-sprd.c | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/drivers/i2c/busses/i2c-sprd.c b/drivers/i2c/busses/i2c-sprd.c
index 066b3a9c30c8..549b60dd3273 100644
--- a/drivers/i2c/busses/i2c-sprd.c
+++ b/drivers/i2c/busses/i2c-sprd.c
@@ -85,6 +85,7 @@ struct sprd_i2c {
 	struct clk *clk;
 	u32 src_clk;
 	u32 bus_freq;
+	bool ack_flag;
 	struct completion complete;
 	struct reset_control *rst;
 	u8 *buf;
@@ -384,7 +385,6 @@ static irqreturn_t sprd_i2c_isr_thread(int irq, void *dev_id)
 {
 	struct sprd_i2c *i2c_dev = dev_id;
 	struct i2c_msg *msg = i2c_dev->msg;
-	bool ack = !(readl(i2c_dev->base + I2C_STATUS) & I2C_RX_ACK);
 	u32 i2c_tran;
 
 	if (msg->flags & I2C_M_RD)
@@ -400,7 +400,7 @@ static irqreturn_t sprd_i2c_isr_thread(int irq, void *dev_id)
 	 * For reading data, ack is always true, if i2c_tran is not 0 which
 	 * means we still need to contine to read data from slave.
 	 */
-	if (i2c_tran && ack) {
+	if (i2c_tran && i2c_dev->ack_flag) {
 		sprd_i2c_data_transfer(i2c_dev);
 		return IRQ_HANDLED;
 	}
@@ -411,7 +411,7 @@ static irqreturn_t sprd_i2c_isr_thread(int irq, void *dev_id)
 	 * If we did not get one ACK from slave when writing data, we should
 	 * return -EIO to notify users.
 	 */
-	if (!ack)
+	if (!i2c_dev->ack_flag)
 		i2c_dev->err = -EIO;
 	else if (msg->flags & I2C_M_RD && i2c_dev->count)
 		sprd_i2c_read_bytes(i2c_dev, i2c_dev->buf, i2c_dev->count);
@@ -428,7 +428,6 @@ static irqreturn_t sprd_i2c_isr(int irq, void *dev_id)
 {
 	struct sprd_i2c *i2c_dev = dev_id;
 	struct i2c_msg *msg = i2c_dev->msg;
-	bool ack = !(readl(i2c_dev->base + I2C_STATUS) & I2C_RX_ACK);
 	u32 i2c_tran;
 
 	if (msg->flags & I2C_M_RD)
@@ -447,7 +446,8 @@ static irqreturn_t sprd_i2c_isr(int irq, void *dev_id)
 	 * means we can read all data in one time, then we can finish this
 	 * transmission too.
 	 */
-	if (!i2c_tran || !ack) {
+	i2c_dev->ack_flag = !(readl(i2c_dev->base + I2C_STATUS) & I2C_RX_ACK);
+	if (!i2c_tran || !i2c_dev->ack_flag) {
 		sprd_i2c_clear_start(i2c_dev);
 		sprd_i2c_clear_irq(i2c_dev);
 	}
-- 
2.17.1

Re: [PATCH 3/8] i2c: sprd: Use global variables to record IIC ack/nack status instead of local variables

Posted by Andi Shyti 2 years, 3 months ago

Hi Huangzheng,

On Thu, Aug 17, 2023 at 05:45:15PM +0800, Huangzheng Lai wrote:
> We found that when the interrupt bit of the IIC controller is cleared,
> the ack/nack bit is also cleared at the same time. After clearing the
> interrupt bit in sprd_i2c_isr(), incorrect ack/nack information will be
> obtained in sprd_i2c_isr_thread(), resulting in incorrect communication
> when nack cannot be recognized. To solve this problem, we used a global
> variable to record ack/nack information before clearing the interrupt
> bit instead of a local variable.
> 
> Signed-off-by: Huangzheng Lai <Huangzheng.Lai@unisoc.com>

Is this a fix? Then please consider adding

Fixes: 8b9ec0719834 ("i2c: Add Spreadtrum I2C controller driver")
Cc: <stable@vger.kernel.org> # v4.14+

> ---
>  drivers/i2c/busses/i2c-sprd.c | 10 +++++-----
>  1 file changed, 5 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/i2c/busses/i2c-sprd.c b/drivers/i2c/busses/i2c-sprd.c
> index 066b3a9c30c8..549b60dd3273 100644
> --- a/drivers/i2c/busses/i2c-sprd.c
> +++ b/drivers/i2c/busses/i2c-sprd.c
> @@ -85,6 +85,7 @@ struct sprd_i2c {
>  	struct clk *clk;
>  	u32 src_clk;
>  	u32 bus_freq;
> +	bool ack_flag;

smells a bit racy... however we are in the same interrupt cycle.

Do you think we might need a spinlock around here?

>  	struct completion complete;
>  	struct reset_control *rst;
>  	u8 *buf;
> @@ -384,7 +385,6 @@ static irqreturn_t sprd_i2c_isr_thread(int irq, void *dev_id)
>  {
>  	struct sprd_i2c *i2c_dev = dev_id;
>  	struct i2c_msg *msg = i2c_dev->msg;
> -	bool ack = !(readl(i2c_dev->base + I2C_STATUS) & I2C_RX_ACK);
>  	u32 i2c_tran;
>  
>  	if (msg->flags & I2C_M_RD)
> @@ -400,7 +400,7 @@ static irqreturn_t sprd_i2c_isr_thread(int irq, void *dev_id)
>  	 * For reading data, ack is always true, if i2c_tran is not 0 which
>  	 * means we still need to contine to read data from slave.
>  	 */
> -	if (i2c_tran && ack) {
> +	if (i2c_tran && i2c_dev->ack_flag) {
>  		sprd_i2c_data_transfer(i2c_dev);
>  		return IRQ_HANDLED;
>  	}
> @@ -411,7 +411,7 @@ static irqreturn_t sprd_i2c_isr_thread(int irq, void *dev_id)
>  	 * If we did not get one ACK from slave when writing data, we should
>  	 * return -EIO to notify users.
>  	 */
> -	if (!ack)
> +	if (!i2c_dev->ack_flag)
>  		i2c_dev->err = -EIO;
>  	else if (msg->flags & I2C_M_RD && i2c_dev->count)
>  		sprd_i2c_read_bytes(i2c_dev, i2c_dev->buf, i2c_dev->count);
> @@ -428,7 +428,6 @@ static irqreturn_t sprd_i2c_isr(int irq, void *dev_id)
>  {
>  	struct sprd_i2c *i2c_dev = dev_id;
>  	struct i2c_msg *msg = i2c_dev->msg;
> -	bool ack = !(readl(i2c_dev->base + I2C_STATUS) & I2C_RX_ACK);
>  	u32 i2c_tran;
>  
>  	if (msg->flags & I2C_M_RD)
> @@ -447,7 +446,8 @@ static irqreturn_t sprd_i2c_isr(int irq, void *dev_id)
>  	 * means we can read all data in one time, then we can finish this
>  	 * transmission too.
>  	 */
> -	if (!i2c_tran || !ack) {
> +	i2c_dev->ack_flag = !(readl(i2c_dev->base + I2C_STATUS) & I2C_RX_ACK);

there is a question from Chunyan here.

I like more

	val = readl(...);
	i2c_dev->ack_flag = !(val & I2C_RX_ACK);

a matter of taste, your choice.

Andi

> +	if (!i2c_tran || !i2c_dev->ack_flag) {
>  		sprd_i2c_clear_start(i2c_dev);
>  		sprd_i2c_clear_irq(i2c_dev);
>  	}
> -- 
> 2.17.1
>

Re: [PATCH 3/8] i2c: sprd: Use global variables to record IIC ack/nack status instead of local variables

Posted by huangzheng lai 2 years, 3 months ago

Hi Andi,

On Sun, Sep 3, 2023 at 5:05 AM Andi Shyti <andi.shyti@kernel.org> wrote:
>
> Hi Huangzheng,
>
> On Thu, Aug 17, 2023 at 05:45:15PM +0800, Huangzheng Lai wrote:
> > We found that when the interrupt bit of the IIC controller is cleared,
> > the ack/nack bit is also cleared at the same time. After clearing the
> > interrupt bit in sprd_i2c_isr(), incorrect ack/nack information will be
> > obtained in sprd_i2c_isr_thread(), resulting in incorrect communication
> > when nack cannot be recognized. To solve this problem, we used a global
> > variable to record ack/nack information before clearing the interrupt
> > bit instead of a local variable.
> >
> > Signed-off-by: Huangzheng Lai <Huangzheng.Lai@unisoc.com>
>
> Is this a fix? Then please consider adding
>
> Fixes: 8b9ec0719834 ("i2c: Add Spreadtrum I2C controller driver")
> Cc: <stable@vger.kernel.org> # v4.14+

Thank you for your prompt. In the next version of the patch, I will
add the fixes tag.

>
> > ---
> >  drivers/i2c/busses/i2c-sprd.c | 10 +++++-----
> >  1 file changed, 5 insertions(+), 5 deletions(-)
> >
> > diff --git a/drivers/i2c/busses/i2c-sprd.c b/drivers/i2c/busses/i2c-sprd.c
> > index 066b3a9c30c8..549b60dd3273 100644
> > --- a/drivers/i2c/busses/i2c-sprd.c
> > +++ b/drivers/i2c/busses/i2c-sprd.c
> > @@ -85,6 +85,7 @@ struct sprd_i2c {
> >       struct clk *clk;
> >       u32 src_clk;
> >       u32 bus_freq;
> > +     bool ack_flag;
>
> smells a bit racy... however we are in the same interrupt cycle.
>
> Do you think we might need a spinlock around here?

The fifo empty and full interrupt enable will be turned off in
sprd_i2c_isr(), and will not be reset until sprd_i2c_isr_thread()
finishes processing, depending on the situation. Apart from these two
interrupt types, there are only two types left: transmission
completion and transmission failure. Both interrupts need to be re
initiated for transmission to occur, and transmission will not be re
initiated until the current data processing is completed.

Thanks,
Huangzheng

Re: [PATCH 3/8] i2c: sprd: Use global variables to record IIC ack/nack status instead of local variables

Posted by Chunyan Zhang 2 years, 3 months ago

On Thu, 17 Aug 2023 at 17:46, Huangzheng Lai <Huangzheng.Lai@unisoc.com> wrote:
>
> We found that when the interrupt bit of the IIC controller is cleared,
> the ack/nack bit is also cleared at the same time. After clearing the
> interrupt bit in sprd_i2c_isr(), incorrect ack/nack information will be
> obtained in sprd_i2c_isr_thread(), resulting in incorrect communication
> when nack cannot be recognized. To solve this problem, we used a global
> variable to record ack/nack information before clearing the interrupt
> bit instead of a local variable.
>
> Signed-off-by: Huangzheng Lai <Huangzheng.Lai@unisoc.com>
> ---
>  drivers/i2c/busses/i2c-sprd.c | 10 +++++-----
>  1 file changed, 5 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/i2c/busses/i2c-sprd.c b/drivers/i2c/busses/i2c-sprd.c
> index 066b3a9c30c8..549b60dd3273 100644
> --- a/drivers/i2c/busses/i2c-sprd.c
> +++ b/drivers/i2c/busses/i2c-sprd.c
> @@ -85,6 +85,7 @@ struct sprd_i2c {
>         struct clk *clk;
>         u32 src_clk;
>         u32 bus_freq;
> +       bool ack_flag;
>         struct completion complete;
>         struct reset_control *rst;
>         u8 *buf;
> @@ -384,7 +385,6 @@ static irqreturn_t sprd_i2c_isr_thread(int irq, void *dev_id)
>  {
>         struct sprd_i2c *i2c_dev = dev_id;
>         struct i2c_msg *msg = i2c_dev->msg;
> -       bool ack = !(readl(i2c_dev->base + I2C_STATUS) & I2C_RX_ACK);
>         u32 i2c_tran;
>
>         if (msg->flags & I2C_M_RD)
> @@ -400,7 +400,7 @@ static irqreturn_t sprd_i2c_isr_thread(int irq, void *dev_id)
>          * For reading data, ack is always true, if i2c_tran is not 0 which
>          * means we still need to contine to read data from slave.
>          */
> -       if (i2c_tran && ack) {
> +       if (i2c_tran && i2c_dev->ack_flag) {
>                 sprd_i2c_data_transfer(i2c_dev);
>                 return IRQ_HANDLED;
>         }
> @@ -411,7 +411,7 @@ static irqreturn_t sprd_i2c_isr_thread(int irq, void *dev_id)
>          * If we did not get one ACK from slave when writing data, we should
>          * return -EIO to notify users.
>          */
> -       if (!ack)
> +       if (!i2c_dev->ack_flag)
>                 i2c_dev->err = -EIO;
>         else if (msg->flags & I2C_M_RD && i2c_dev->count)
>                 sprd_i2c_read_bytes(i2c_dev, i2c_dev->buf, i2c_dev->count);
> @@ -428,7 +428,6 @@ static irqreturn_t sprd_i2c_isr(int irq, void *dev_id)
>  {
>         struct sprd_i2c *i2c_dev = dev_id;
>         struct i2c_msg *msg = i2c_dev->msg;
> -       bool ack = !(readl(i2c_dev->base + I2C_STATUS) & I2C_RX_ACK);
>         u32 i2c_tran;
>
>         if (msg->flags & I2C_M_RD)
> @@ -447,7 +446,8 @@ static irqreturn_t sprd_i2c_isr(int irq, void *dev_id)
>          * means we can read all data in one time, then we can finish this
>          * transmission too.
>          */
> -       if (!i2c_tran || !ack) {
> +       i2c_dev->ack_flag = !(readl(i2c_dev->base + I2C_STATUS) & I2C_RX_ACK);

Do we need clear i2c_dev->ack_flag in sprd_i2c_clear_ack()?

> +       if (!i2c_tran || !i2c_dev->ack_flag) {
>                 sprd_i2c_clear_start(i2c_dev);
>                 sprd_i2c_clear_irq(i2c_dev);
>         }
> --
> 2.17.1
>

[PATCH 1/8] i2c: sprd: Add configurations that support 1Mhz and 3.4Mhz frequencies
[PATCH 2/8] i2c: sprd: Add I2C driver to use 'reset framework' function
[PATCH 3/8] i2c: sprd: Use global variables to record IIC ack/nack status instead of local variables
[PATCH 4/8] i2c: sprd: Add IIC controller driver to support dynamic switching of 400K/1M/3.4M frequency
[PATCH 5/8] i2c: sprd: Configure the enable bit of the IIC controller before each transmission initiation
[PATCH 6/8] i2c: sprd: Add additional IIC control bit configuration to adapt to the new IP version of the UNISOC platform
[PATCH 7/8] i2c: sprd: Set I2C_RX_ACK when clear irq
[PATCH 8/8] i2c: sprd: Increase the waiting time for IIC transmission to avoid system crash issues