Re: [PATCH v6 03/15] drm/bridge: tc358767: Simplify polling in tc_link_training()

[Tomi Valkeinen]

On 04/12/2019 20:27, Tomi Valkeinen wrote:
> 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,
> > Â static int tc_wait_link_training(struct tc_data *tc)
> > Â {
> > -ÂÂÂ u32 timeout = 1000;
> > ÂÂÂÂÂ u32 value;
> > ÂÂÂÂÂ int ret;
> > -ÂÂÂ do {
> > -ÂÂÂÂÂÂÂ udelay(1);
> > -ÂÂÂÂÂÂÂ tc_read(DP0_LTSTAT, &value);
> > -ÂÂÂ } while ((!(value & LT_LOOPDONE)) && (--timeout));
> > -
> > -ÂÂÂ if (timeout == 0) {
> > +ÂÂÂ ret = tc_poll_timeout(tc, DP0_LTSTAT, LT_LOOPDONE,
> > +ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ 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.

Also the timeout in tc_aux_link_setup takes ~500us for me, and max is 1000us. So it works, but I 
think it's a bit tight.

 Tomi

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