Am Mittwoch, dem 02.10.2024 um 13:19 +0200 schrieb Stefan Eichenberger:
> From: Stefan Eichenberger <stefan.eichenberger@xxxxxxxxxxx>
>
> According to the i.MX8M Mini reference manual chapter "16.1.4.2
> Generation of Start" it is only necessary to poll for bus busy and
> arbitration lost in multi master mode. This helps to avoid rescheduling
> while the i2c bus is busy and avoids SMBus devices to timeout.
>
This is a backward incompatible change, as far as I can see. Until now
the driver would properly handle a multi-mastered bus, without any
specific configuration. Now it requires the new multi-master DT
property to be set, which isn't even documented in the binding to be
understood by this driver.
Are you sure that every single instance of a i.MX i2c bus is only
single mastered?
If this is a worthwhile performance improvement I guess you need to
flip the logic around by adding a new single-master DT property (or
something along those lines), which should go through proper DT binding
review. You can then use this property for boards/busses to opt into
skipping the arbitration lost check.
Regards,
Lucas
> Signed-off-by: Stefan Eichenberger <stefan.eichenberger@xxxxxxxxxxx>
> Reviewed-by: Frank Li <Frank.Li@xxxxxxx>
> Acked-by: Oleksij Rempel <o.rempel@xxxxxxxxxxxxxx>
> ---
> drivers/i2c/busses/i2c-imx.c | 11 +++++++++--
> 1 file changed, 9 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/i2c/busses/i2c-imx.c b/drivers/i2c/busses/i2c-imx.c
> index 98539313cbc97..fbacdfaf6b28e 100644
> --- a/drivers/i2c/busses/i2c-imx.c
> +++ b/drivers/i2c/busses/i2c-imx.c
> @@ -216,6 +216,8 @@ struct imx_i2c_struct {
> struct i2c_client *slave;
> enum i2c_slave_event last_slave_event;
>
> + bool multi_master;
> +
> /* For checking slave events. */
> spinlock_t slave_lock;
> struct hrtimer slave_timer;
> @@ -481,6 +483,9 @@ 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;
> +
> while (1) {
> temp = imx_i2c_read_reg(i2c_imx, IMX_I2C_I2SR);
>
> @@ -540,8 +545,8 @@ static int i2c_imx_trx_complete(struct imx_i2c_struct *i2c_imx, bool atomic)
> return -ETIMEDOUT;
> }
>
> - /* check for arbitration lost */
> - if (i2c_imx->i2csr & I2SR_IAL) {
> + /* In multi-master mode check for arbitration lost */
> + if (i2c_imx->multi_master && (i2c_imx->i2csr & I2SR_IAL)) {
> dev_dbg(&i2c_imx->adapter.dev, "<%s> Arbitration lost\n", __func__);
> i2c_imx_clear_irq(i2c_imx, I2SR_IAL);
>
> @@ -1468,6 +1473,8 @@ static int i2c_imx_probe(struct platform_device *pdev)
> goto rpm_disable;
> }
>
> + i2c_imx->multi_master = of_property_read_bool(pdev->dev.of_node, "multi-master");
> +
> /* Set up clock divider */
> i2c_imx->bitrate = I2C_MAX_STANDARD_MODE_FREQ;
> ret = of_property_read_u32(pdev->dev.of_node,
