Quoting Jacopo Mondi (2021-11-04 11:09:23)
> Valid pixel clock detection is performed by spinning on a register read
> which if repeated too frequently might fail. As the error is not fatal
> ignore it instead of bailing out to continue spinning until the timeout
> completion.
>
> Also relax the time between bus transactions and slightly increase the
> wait interval to mitigate the failure risk.
>
> Signed-off-by: Jacopo Mondi <jacopo+renesas@xxxxxxxxxx>
> Reviewed-by: Niklas Söderlund <niklas.soderlund+renesas@xxxxxxxxxxxx>
This seems good to me. In your testing did you identify how many
spins/how long it usually takes before it first detects the pixel clock?
I.e. - was it cutting it close at 10ms, and we should even still extend
this further? (as the usleep_range means we could still loop this 10 ms)
Anyway, this looks like a strong improvement.
Reviewed-by: Kieran Bingham <kieran.bingham+renesas@xxxxxxxxxxxxxxxx>
> ---
>
> v1->v2:
> - Do not continue but jump to a label to respect the sleep timout after a
> failed read
>
> Niklas I kept your tag anyway, hope it's ok.
>
> Thanks
> j
>
> ---
> drivers/media/i2c/max9271.c | 9 +++++----
> 1 file changed, 5 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/media/i2c/max9271.c b/drivers/media/i2c/max9271.c
> index ff86c8c4ea61..aa4add473716 100644
> --- a/drivers/media/i2c/max9271.c
> +++ b/drivers/media/i2c/max9271.c
> @@ -55,7 +55,7 @@ static int max9271_write(struct max9271_device *dev, u8 reg, u8 val)
> /*
> * max9271_pclk_detect() - Detect valid pixel clock from image sensor
> *
> - * Wait up to 10ms for a valid pixel clock.
> + * Wait up to 15ms for a valid pixel clock.
> *
> * Returns 0 for success, < 0 for pixel clock not properly detected
> */
> @@ -64,15 +64,16 @@ static int max9271_pclk_detect(struct max9271_device *dev)
> unsigned int i;
> int ret;
>
> - for (i = 0; i < 100; i++) {
> + for (i = 0; i < 10; i++) {
> ret = max9271_read(dev, 0x15);
> if (ret < 0)
> - return ret;
> + goto skip;
>
> if (ret & MAX9271_PCLKDET)
> return 0;
>
> - usleep_range(50, 100);
> +skip:
> + usleep_range(1000, 1500);
> }
>
> dev_err(&dev->client->dev, "Unable to detect valid pixel clock\n");
> --
> 2.33.1
>
