Hi Stefan,
On Mon, Dec 16, 2024 at 04:16:40PM +0100, Stefan Eichenberger wrote:
> From: Stefan Eichenberger <stefan.eichenberger@xxxxxxxxxxx>
>
> A regression was introduced with the implementation of single-master
> mode, preventing proper stop conditions from being generated. Devices
> that require a valid stop condition, such as EEPROMs, fail to function
> correctly as a result.
>
> The issue only affects devices with the single-master property enabled.
>
> This commit resolves the issue by re-enabling I2C bus busy bit (IBB)
> polling for single-master mode when generating a stop condition. The fix
> further ensures that the i2c_imx->stopped flag is cleared at the start
> of each transfer, allowing the stop condition to be correctly generated
> in i2c_imx_stop().
>
> According to the reference manual (IMX8MMRM, Rev. 2, 09/2019, page
> 5270), polling the IBB bit to determine if the bus is free is only
> necessary in multi-master mode. Consequently, the IBB bit is not polled
> for the start condition in single-master mode.
>
> Fixes: 6692694aca86 ("i2c: imx: do not poll for bus busy in single master mode")
> Signed-off-by: Stefan Eichenberger <stefan.eichenberger@xxxxxxxxxxx>
> ---
> drivers/i2c/busses/i2c-imx.c | 8 +++-----
> 1 file changed, 3 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/i2c/busses/i2c-imx.c b/drivers/i2c/busses/i2c-imx.c
> index f751d231ded8..cbf66a69e20b 100644
> --- a/drivers/i2c/busses/i2c-imx.c
> +++ b/drivers/i2c/busses/i2c-imx.c
> @@ -534,20 +534,18 @@ static int i2c_imx_bus_busy(struct imx_i2c_struct *i2c_imx, int for_busy, bool a
> {
> unsigned long orig_jiffies = jiffies;
> unsigned int temp;
> -
> - if (!i2c_imx->multi_master)
> - return 0;
> + bool multi_master = i2c_imx->multi_master;
with this small adjustment, I have applied your patch to
i2c/i2c-host-fixes.
The idea behind the change is that variables are sorted by
length, forming a kind of reversed Christmas tree shape. It's
not a strict rule—some communities enforce it, others don't, and
some follow entirely different conventions.
Since it feels somewhat arbitrary to me, I don't enforce it
strictly. However, I personally try to adhere to the reversed
Christmas tree rule whenever possible.
Andi
>
> while (1) {
> temp = imx_i2c_read_reg(i2c_imx, IMX_I2C_I2SR);
>
> /* check for arbitration lost */
> - if (temp & I2SR_IAL) {
> + if (multi_master && (temp & I2SR_IAL)) {
> i2c_imx_clear_irq(i2c_imx, I2SR_IAL);
> return -EAGAIN;
> }
>
> - if (for_busy && (temp & I2SR_IBB)) {
> + if (for_busy && (!multi_master || (temp & I2SR_IBB))) {
> i2c_imx->stopped = 0;
> break;
> }
> --
> 2.45.2
>
