linux-kernel - Re: [PATCH 1/2] drm/bridge: parade-ps8640: Enable runtime power management

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Message-ID: <CAD=FV=V7+MzyjsLKE87c=8bkFiRbQkGoM4Jfm8jcsJBG0aYAWw@mail.gmail.com>
Date:   Mon, 18 Oct 2021 13:42:58 -0700
From:   Doug Anderson <dianders@...omium.org>
To:     Philip Chen <philipchen@...omium.org>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Stephen Boyd <swboyd@...omium.org>,
        Andrzej Hajda <a.hajda@...sung.com>,
        Daniel Vetter <daniel@...ll.ch>,
        David Airlie <airlied@...ux.ie>,
        Jernej Skrabec <jernej.skrabec@...il.com>,
        Jonas Karlman <jonas@...boo.se>,
        Laurent Pinchart <Laurent.pinchart@...asonboard.com>,
        Neil Armstrong <narmstrong@...libre.com>,
        Robert Foss <robert.foss@...aro.org>,
        dri-devel <dri-devel@...ts.freedesktop.org>
Subject: Re: [PATCH 1/2] drm/bridge: parade-ps8640: Enable runtime power management

Hi,

On Sat, Oct 16, 2021 at 9:57 AM Philip Chen <philipchen@...omium.org> wrote:
>
> @@ -319,81 +345,70 @@ static void ps8640_bridge_poweron(struct ps8640 *ps_bridge)
>          */
>         msleep(200);
>
> -       ret = regmap_read_poll_timeout(map, PAGE2_GPIO_H, status,
> -                                      status & PS_GPIO9, 20 * 1000, 200 * 1000);
> -
> -       if (ret < 0) {
> -               DRM_ERROR("failed read PAGE2_GPIO_H: %d\n", ret);
> -               goto err_regulators_disable;
> -       }

Above the "msleep(200)" I see a comment that says "and then check the
MCU ready flag every 20ms". That probably refers to the code that
you're moving here. Maybe change the comment above the "msleep(200);"
to something like this if you like it:

/*
 * Mystery 200 ms delay for the "MCU to be ready". It's unclear if
 * this is truly necessary since the MCU will already signal that
 * things are "good to go" by signaling HPD on "gpio 9". See
 * ps8640_ensure_hpd(). For now we'll keep this mystery delay just in
 * case.
 */

Other than that this looks good to me, which isn't really a surprise
since I was involved in helping with / reviewing early versions of
this change. In any case, I'm happy with:

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