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SubjectRe: [PATCH v6 03/15] drm/bridge: tc358767: Simplify polling in tc_link_training()
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Hi Andrey,

On 19/06/2019 08:27, Andrey Smirnov wrote:

> @@ -748,22 +748,19 @@ static int tc_set_video_mode(struct tc_data *tc,
>
> static int tc_wait_link_training(struct tc_data *tc)
> {
> - u32 timeout = 1000;
> u32 value;
> int ret;
>
> - do {
> - udelay(1);
> - tc_read(DP0_LTSTAT, &value);
> - } while ((!(value & LT_LOOPDONE)) && (--timeout));
> -
> - if (timeout == 0) {
> + ret = tc_poll_timeout(tc, DP0_LTSTAT, LT_LOOPDONE,
> + LT_LOOPDONE, 1, 1000);

This seems to break DP at least with some monitors for me. I think it's just a timeout problem, as
increasing the values helps.

Using ktime, I can see that during link training, the first call takes ~2ms, the second ~7ms. I
think this worked before, as udelay(1) takes much longer than 1 us.

We have 1000us limit in a few other places too, which I don't see causing issues, but might need
increasing too.

Also, 1us sleep_us may be a bit too small to be sane. If the loops take milliseconds, probably 100us
or even more would make sense.

This didn't cause any issues with your display?

Tomi

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