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

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Message-ID: <CAAfSe-uv-PrUHXFT=LGQAr1=ptBpfkcfT1LODi5ALJR8qTjH7g@mail.gmail.com>
Date:   Thu, 31 Aug 2023 15:04:08 +0800
From:   Chunyan Zhang <zhang.lyra@...il.com>
To:     Huangzheng Lai <Huangzheng.Lai@...soc.com>
Cc:     Andi Shyti <andi.shyti@...nel.org>,
        Orson Zhai <orsonzhai@...il.com>,
        Baolin Wang <baolin.wang@...ux.alibaba.com>,
        linux-i2c@...r.kernel.org, linux-kernel@...r.kernel.org,
        huangzheng lai <laihuangzheng@...il.com>,
        Xiongpeng Wu <xiongpeng.wu@...soc.com>
Subject: Re: [PATCH 3/8] i2c: sprd: Use global variables to record IIC
 ack/nack status instead of local variables

On Thu, 17 Aug 2023 at 17:46, Huangzheng Lai <Huangzheng.Lai@...soc.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@...soc.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
>