linux-kernel - Re: [PATCH v2 4/4] drm/bridge: ti-sn65dsi86: Update reply on aux failures

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Date:   Mon, 2 Nov 2020 08:30:35 -0800
From:   Doug Anderson <dianders@...omium.org>
To:     Stephen Boyd <swboyd@...omium.org>
Cc:     Andrzej Hajda <a.hajda@...sung.com>,
        Neil Armstrong <narmstrong@...libre.com>,
        LKML <linux-kernel@...r.kernel.org>,
        dri-devel <dri-devel@...ts.freedesktop.org>,
        Laurent Pinchart <Laurent.pinchart@...asonboard.com>,
        Jonas Karlman <jonas@...boo.se>,
        Jernej Skrabec <jernej.skrabec@...l.net>,
        Sean Paul <seanpaul@...omium.org>
Subject: Re: [PATCH v2 4/4] drm/bridge: ti-sn65dsi86: Update reply on aux failures

Hi,

On Thu, Oct 29, 2020 at 6:17 PM Stephen Boyd <swboyd@...omium.org> wrote:
>
> We should be setting the drm_dp_aux_msg::reply field if a NACK or a
> SHORT reply happens. Update the error bit handling logic in
> ti_sn_aux_transfer() to handle these cases and notify upper layers that
> such errors have happened. This helps the retry logic understand that a
> timeout has happened, or to shorten the read length if the panel isn't
> able to handle the longest read possible.
>
> Note: I don't have any hardware that exhibits these code paths so this
> is written based on reading the datasheet for this bridge and inspecting
> the code and how this is called.
>
> Changes in v2:
>  - Handle WRITE_STATUS_UPDATE properly
>
> Cc: Douglas Anderson <dianders@...omium.org>
> Cc: Laurent Pinchart <Laurent.pinchart@...asonboard.com>
> Cc: Jonas Karlman <jonas@...boo.se>
> Cc: Jernej Skrabec <jernej.skrabec@...l.net>
> Cc: Sean Paul <seanpaul@...omium.org>
> Signed-off-by: Stephen Boyd <swboyd@...omium.org>
> ---
>  drivers/gpu/drm/bridge/ti-sn65dsi86.c | 36 ++++++++++++++++++++++++---
>  1 file changed, 32 insertions(+), 4 deletions(-)

This looks right to me, now.  Hopefully if/when someone ends up with
hardware that exercises these codepaths they'll at least be in a
better state and maybe they will all just work!  :-)

Reviewed-by: Douglas Anderson <dianders@...omium.org>