linux-kernel - Re: [PATCH] drm/bridge: ps8640: Add software to support aux defer

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Message-ID: <CAD=FV=Xauvh1XhMUQZc8cp3-Wo4TRgD1waLiwAXP5z8EBW9Nrg@mail.gmail.com>
Date:   Thu, 29 Sep 2022 08:41:05 -0700
From:   Doug Anderson <dianders@...omium.org>
To:     Jason Yen <jason.yen@...adetech.corp-partner.google.com>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Andrzej Hajda <andrzej.hajda@...el.com>,
        Neil Armstrong <neil.armstrong@...aro.org>,
        Robert Foss <robert.foss@...aro.org>,
        Laurent Pinchart <Laurent.pinchart@...asonboard.com>,
        Jonas Karlman <jonas@...boo.se>,
        Jernej Skrabec <jernej.skrabec@...il.com>,
        David Airlie <airlied@...il.com>,
        Daniel Vetter <daniel@...ll.ch>,
        dri-devel <dri-devel@...ts.freedesktop.org>,
        Pin-yen Lin <treapking@...gle.com>
Subject: Re: [PATCH] drm/bridge: ps8640: Add software to support aux defer

Hi,

On Wed, Sep 28, 2022 at 6:29 PM Jason Yen
<jason.yen@...adetech.corp-partner.google.com> wrote:
>
> This chip can not handle aux defer if the host directly program
> its aux registers to access edid/dpcd. So we need let software
> to handle the aux defer situation.
>
> Signed-off-by: Jason Yen <jason.yen@...adetech.corp-partner.google.com>
> ---
>
>  drivers/gpu/drm/bridge/parade-ps8640.c | 8 ++++++++
>  1 file changed, 8 insertions(+)
>
> diff --git a/drivers/gpu/drm/bridge/parade-ps8640.c b/drivers/gpu/drm/bridge/parade-ps8640.c
> index 31e88cb39f8a..967dec840b91 100644
> --- a/drivers/gpu/drm/bridge/parade-ps8640.c
> +++ b/drivers/gpu/drm/bridge/parade-ps8640.c
> @@ -303,6 +303,14 @@ static ssize_t ps8640_aux_transfer_msg(struct drm_dp_aux *aux,
>         case SWAUX_STATUS_ACKM:
>                 len = data & SWAUX_M_MASK;
>                 break;
> +       case SWAUX_STATUS_DEFER:
> +       case SWAUX_STATUS_I2C_DEFER:
> +               if (is_native_aux)
> +                       msg->reply |= DP_AUX_NATIVE_REPLY_DEFER;
> +               else
> +                       msg->reply |= DP_AUX_I2C_REPLY_DEFER;
> +               len = data & SWAUX_M_MASK;
> +               break;

Overall this looks OK to me, but please send a v2 that removes the
line above that states:

/* Ignore the DEFER cases as they are already handled in hardware */

-Doug