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@xxxxxxxxxx>
Is this a fix? Then please consider adding
Fixes: 8b9ec0719834 ("i2c: Add Spreadtrum I2C controller driver")
Cc: <stable@xxxxxxxxxxxxxxx> # 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
>
