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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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