linux-kernel - Re: [PATCH v8 02/10] drm/vc4: hdmi: Fix HPD GPIO detection

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Message-ID: <CAPY8ntCu=wzXtNeDrnYNC8NH8WwjUY-qC=UsgqS_VQO1voR8SA@mail.gmail.com>
Date:   Tue, 2 Nov 2021 16:15:59 +0000
From:   Dave Stevenson <dave.stevenson@...pberrypi.com>
To:     Maxime Ripard <maxime@...no.tech>
Cc:     DRI Development <dri-devel@...ts.freedesktop.org>,
        Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        Daniel Vetter <daniel.vetter@...el.com>,
        David Airlie <airlied@...ux.ie>,
        linux-rpi-kernel@...ts.infradead.org,
        LKML <linux-kernel@...r.kernel.org>,
        Maxime Ripard <mripard@...nel.org>,
        Nicolas Saenz Julienne <nsaenz@...nel.org>,
        bcm-kernel-feedback-list@...adcom.com,
        Emma Anholt <emma@...olt.net>,
        Phil Elwell <phil@...pberrypi.com>,
        Tim Gover <tim.gover@...pberrypi.com>,
        Dom Cobley <dom@...pberrypi.com>
Subject: Re: [PATCH v8 02/10] drm/vc4: hdmi: Fix HPD GPIO detection

On Mon, 25 Oct 2021 at 16:29, Maxime Ripard <maxime@...no.tech> wrote:
>
> Prior to commit 6800234ceee0 ("drm/vc4: hdmi: Convert to gpiod"), in the
> detect hook, if we had an HPD GPIO we would only rely on it and return
> whatever state it was in.
>
> However, that commit changed that by mistake to only consider the case
> where we have a GPIO and it returns a logical high, and would fall back
> to the other methods otherwise.
>
> Since we can read the EDIDs when the HPD signal is low on some displays,
> we changed the detection status from disconnected to connected, and we
> would ignore an HPD pulse.
>
> Fixes: 6800234ceee0 ("drm/vc4: hdmi: Convert to gpiod")
> Signed-off-by: Maxime Ripard <maxime@...no.tech>

Reviewed-by: Dave Stevenson <dave.stevenson@...pberrypi.com>

> ---
>  drivers/gpu/drm/vc4/vc4_hdmi.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/gpu/drm/vc4/vc4_hdmi.c b/drivers/gpu/drm/vc4/vc4_hdmi.c
> index 338968275724..dde67b991ae7 100644
> --- a/drivers/gpu/drm/vc4/vc4_hdmi.c
> +++ b/drivers/gpu/drm/vc4/vc4_hdmi.c
> @@ -190,9 +190,9 @@ vc4_hdmi_connector_detect(struct drm_connector *connector, bool force)
>
>         WARN_ON(pm_runtime_resume_and_get(&vc4_hdmi->pdev->dev));
>
> -       if (vc4_hdmi->hpd_gpio &&
> -           gpiod_get_value_cansleep(vc4_hdmi->hpd_gpio)) {
> -               connected = true;
> +       if (vc4_hdmi->hpd_gpio) {
> +               if (gpiod_get_value_cansleep(vc4_hdmi->hpd_gpio))
> +                       connected = true;
>         } else {
>                 unsigned long flags;
>                 u32 hotplug;
> --
> 2.31.1
>