linux-kernel - Re: [Intel-gfx] [PATCH v2] drm/i915/display/lspcon: Increase LSPCON mode settle timeout

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Message-ID: <a2b08289-e7d0-3003-5fd3-fe3a437cb967@intel.com>
Date:   Mon, 10 Jul 2023 09:32:59 +0530
From:   "Nautiyal, Ankit K" <ankit.k.nautiyal@...el.com>
To:     Pablo Ceballos <pceballos@...gle.com>
CC:     David Airlie <airlied@...il.com>, Daniel Vetter <daniel@...ll.ch>,
        <intel-gfx@...ts.freedesktop.org>, <linux-kernel@...r.kernel.org>,
        <dri-devel@...ts.freedesktop.org>,
        Rodrigo Vivi <rodrigo.vivi@...el.com>,
        Sam Ravnborg <sam@...nborg.org>
Subject: Re: [Intel-gfx] [PATCH v2] drm/i915/display/lspcon: Increase LSPCON
 mode settle timeout


On 7/8/2023 1:04 AM, Pablo Ceballos wrote:
> On Wed, Jun 14, 2023 at 9:35 PM Nautiyal, Ankit K
> <ankit.k.nautiyal@...el.com> wrote:
>> I was wondering if trying to set LS/PCON mode multiple time will have
>> any effect.
>>
>> Unfortunately I do not have access to machine with Parade LSPCON chip,
>> had suggested in yet another git lab issue [2].
>>
>> I have a patch for this, sent to try-bot, though not sent to intel-gfx
>> yet [3].
> I tested this patch and it did not resolve the problem. The error log
> was repeated multiple times and there were still link training issues
> afterwards.

Really appreciate to try this thing out, thanks. Too bad it didn't 
workout :(

I have seen increasing timeout does improves situation, but didn't have 
enough data points to come to a timeout value.

I agree with the change based on the experiments and data you have shared.

Lets just change the timeout to 800 ms when the lspcon->vendor is 
LSPCON_VENDOR_PARADE, so that it doesn't have any effect on platforms 
that don't have this.

IMHO a function to get timeout value based on lspcon vendor will be 
better (returns 800 ms for Parade, 400 otherwise.)

In the function itself, we can have the explanation of arriving at 800 
ms for the Parade chip (as given in the commit message) as a comment.


Thanks again for trying different solutions.

Regards,

Ankit


>> The timeout value was already increased from 100 ms to 400 ms earlier too.
>>
>> If there is indeed no other way, perhaps need to have this solution.
> Yes, can this please be merged?
>
> Regards,
> Pablo