Hi Patrice, Pierre-Yves, Alain

On Tue, Jun 1, 2021 at 7:43 PM Patrice CHOTARD patrice.chotard@foss.st.com wrote:

Hi Dillon

On 5/14/21 1:02 PM, dillon.minfei@gmail.com wrote:

...

From: Dillon Min dillon.minfei@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 bring in side effect, introduce IIC_LAST_BYTE_POS to support xip kernel or zImage.

Fixes: 62817fc8d282 ("i2c: stm32f4: add driver") Link: https://lore.kernel.org/lkml/1591709203-12106-5-git-send-email-dillon.minfei... Signed-off-by: Dillon Min dillon.minfei@gmail.com

---

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 4933fc8ce3fd..2e41231b9037 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
  
  

I tested this patch on STM32F429-Disco, it fixes the issue described by Dillon. But i think it's not a good idea to make usage of #if !defined(CONFIG_MMU) && !defined(CONFIG_XIP_KERNEL) inside the driver code.

Hi Patrice, Thanks for your time.

How about introducing a dts node for this purpose. like stm32-i2c,last-byte-pos = <1>; or stm32-i2c,last-byte-pos = <2>;

if not set, the default value is 2

Best Regards Dillon

Pierre-Yves, Alain, as i am not I2C expert, can you have a look at this patch and propose another solution to fix the original issue described by Dillon ?

Thanks Patrice