[PATCH v4 4/4] i2c: stm32f4: Fix stmpe811 get xyz data timeout issue

[dillon min]

Hi All,

Just a gentle ping.

Regards.

On Tue, Jun 9, 2020 at 9:27 PM <dillon.minfei at gmail.com> wrote:
>
> From: dillon min <dillon.minfei at gmail.com>
>
> as stm32f429's internal flash is 2Mbytes and compiled kernel
> image bigger than 2Mbytes, so we have to load kernel image
> to sdram on stm32f429-disco board which has 8Mbytes sdram space.
>
> based on above context, as you knows kernel running on external
> sdram is more slower than internal flash. besides, we need read 4
> bytes to get touch screen xyz(x, y, pressure) coordinate data in
> stmpe811 interrupt.
>
> so, in stm32f4_i2c_handle_rx_done, as i2c read slower than running
> in xip mode, have to adjust 'STOP/START bit set position' from last
> two bytes to last one bytes. else, will get i2c timeout in reading
> touch screen coordinate.
>
> to not take side effect, introduce IIC_LAST_BYTE_POS to support xip
> kernel or has mmu platform.
>
> Signed-off-by: dillon min <dillon.minfei at gmail.com>
> ---
>
> V4: indroduce 'IIC_LAST_BYTE_POS' to compatible with xipkernel boot
>
>  drivers/i2c/busses/i2c-stm32f4.c | 12 +++++++++---
>  1 file changed, 9 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/i2c/busses/i2c-stm32f4.c b/drivers/i2c/busses/i2c-stm32f4.c
> index d6a69dfcac3f..97cf42ae7fa0 100644
> --- a/drivers/i2c/busses/i2c-stm32f4.c
> +++ b/drivers/i2c/busses/i2c-stm32f4.c
> @@ -93,6 +93,12 @@
>  #define STM32F4_I2C_MAX_FREQ           46U
>  #define HZ_TO_MHZ                      1000000
>
> +#if !defined(CONFIG_MMU) && !defined(CONFIG_XIP_KERNEL)
> +#define IIC_LAST_BYTE_POS 1
> +#else
> +#define IIC_LAST_BYTE_POS 2
> +#endif
> +
>  /**
>   * struct stm32f4_i2c_msg - client specific data
>   * @addr: 8-bit slave addr, including r/w bit
> @@ -439,7 +445,7 @@ static void stm32f4_i2c_handle_rx_done(struct stm32f4_i2c_dev *i2c_dev)
>         int i;
>
>         switch (msg->count) {
> -       case 2:
> +       case IIC_LAST_BYTE_POS:
>                 /*
>                  * In order to correctly send the Stop or Repeated Start
>                  * condition on the I2C bus, the STOP/START bit has to be set
> @@ -454,7 +460,7 @@ static void stm32f4_i2c_handle_rx_done(struct stm32f4_i2c_dev *i2c_dev)
>                 else
>                         stm32f4_i2c_set_bits(reg, STM32F4_I2C_CR1_START);
>
> -               for (i = 2; i > 0; i--)
> +               for (i = IIC_LAST_BYTE_POS; i > 0; i--)
>                         stm32f4_i2c_read_msg(i2c_dev);
>
>                 reg = i2c_dev->base + STM32F4_I2C_CR2;
> @@ -463,7 +469,7 @@ static void stm32f4_i2c_handle_rx_done(struct stm32f4_i2c_dev *i2c_dev)
>
>                 complete(&i2c_dev->complete);
>                 break;
> -       case 3:
> +       case (IIC_LAST_BYTE_POS+1):
>                 /*
>                  * In order to correctly generate the NACK pulse after the last
>                  * received data byte, we have to enable NACK before reading N-2
> --
> 2.7.4
>