[PATCH] drm/bridge: tc358767: fix poll timeouts

[Tomi Valkeinen]

Hi Andrzej,

On 09/12/2019 16:45, Andrey Smirnov wrote:
> + Chris Healy
> 
> On Mon, Dec 9, 2019 at 12:27 AM Tomi Valkeinen <tomi.valkeinen at ti.com> wrote:
>>
>> Link training fails with:
>>
>>    Link training timeout waiting for LT_LOOPDONE!
>>    main link enable error: -110
>>
>> This is caused by too tight timeouts, which were changed recently in
>> aa92213f388b ("drm/bridge: tc358767: Simplify polling in tc_link_training()").
>>
>> With a quick glance, the commit does not change the timeouts. However,
>> the method of delaying/sleeping is different, and as the timeout in the
>> previous implementation was not explicit, the new version in practice
>> has much tighter timeout.
>>
>> The same change was made to other parts in the driver, but the link
>> training timeout is the only one I have seen causing issues.
>> Nevertheless, 1 us sleep is not very sane, and the timeouts look pretty
>> tight, so lets fix all the timeouts.
>>
>> One exception was the aux busy poll, where the poll sleep was much
>> longer than necessary (or optimal).
>>
>> I measured the times on my setup, and now the sleep times are set to
>> such values that they result in multiple loops, but not too many (say,
>> 5-10 loops). The timeouts were all increased to 100ms, which should be
>> more than enough for all of these, but in case of bad errors, shouldn't
>> stop the driver as multi-second timeouts could do.
>>
>> Signed-off-by: Tomi Valkeinen <tomi.valkeinen at ti.com>
>> Fixes: aa92213f388b ("drm/bridge: tc358767: Simplify polling in tc_link_training()")
> 
> Tested on RDU2 with TC358767/eDP panel, doesn't seem to break anything
> there, so:
> 
> Tested-by: Andrey Smirnov <andrew.smirnov at gmail.com>

Andrzej, can you pick this up for -fixes?

  Tomi

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