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

[Neil Armstrong]

On 13/01/2020 14:31, Tomi Valkeinen wrote:
> 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
> 

Reviewed-by: Neil Armstrong <narmstrong at baylibre.com>

Applied to drm-misc-fixes

Neil