Re: [PATCH 1/2] i2c: imx: do not carry the interrupt status over to the next transfer

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found no new issues
in this patch, but noticed 1 related pre-existing issue it does not
introduce:
- [High] i2c: imx: incorrect message index for I2C_M_RECV_LEN check in
  i2c_imx_xfer_common() [1]
--

commit 264afe43ed92a8a97214ca4df23166f59bf1e387
Author: Mehmet Fide <mehmet.fide@screeningeagle.com>

i2c: imx: do not carry the interrupt status over to the next transfer

This commit clears i2c_imx->i2csr at the start of i2c_imx_xfer_common() so
that stale interrupt status from a failed DMA transfer does not cause a
subsequent DMA read to complete prematurely.

> diff --git a/drivers/i2c/busses/i2c-imx.c b/drivers/i2c/busses/i2c-imx.c
> index ccf08cd63151f..1987a0fd81329 100644
> --- a/drivers/i2c/busses/i2c-imx.c
> +++ b/drivers/i2c/busses/i2c-imx.c
> @@ -1657,6 +1657,8 @@ static int i2c_imx_xfer_common(struct i2c_adapter *adapter,
>  	if (result)
>  		return result;
>  
> +	i2c_imx->i2csr = 0;
> +
>  	/* Start I2C transfer */
>  	result = i2c_imx_start(i2c_imx, atomic);
>  	if (result) {

[Severity: High]
This problem wasn't introduced by this patch, but should block_data check
msgs[i].flags instead of msgs->flags [1] in the message loop of
i2c_imx_xfer_common()?

drivers/i2c/busses/i2c-imx.c:i2c_imx_xfer_common() {
    ...
		if (msgs[i].flags & I2C_M_RD) {
			int block_data = msgs->flags & I2C_M_RECV_LEN;

			if (atomic)
				result = i2c_imx_atomic_read(i2c_imx, &msgs[i], is_lastmsg);
			else if (use_dma && !block_data)
				result = i2c_imx_dma_read(i2c_imx, &msgs[i], is_lastmsg);
    ...
}

In a combined transfer such as an SMBus block read where msgs[0] is a
command write and msgs[1] is a DMA-eligible read with I2C_M_RECV_LEN set,
msgs->flags tests msgs[0].flags, so block_data is 0 for msgs[1].  That
routes msgs[1] to i2c_imx_dma_read(), which does not parse the initial
SMBus block length byte and corrupts or fails the read.

[1] https://sashiko.dev/#/bug/linux-f62df5ed-ad96-43f2-872a-ae2c0100b73f

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20261113073250.1037215-1-mehmet.fide@gmail.com?part=1