linux-kernel - Re: [PATCH v4 11/12] drm/vc4: hdmi: Add a workqueue to set scrambling

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Message-ID: <CAPY8ntCmQOdXMPth_J3FmWi2a-GZuz5wTyfyQOWgpNBCWnUXFA@mail.gmail.com>
Date:   Fri, 21 May 2021 18:43:42 +0100
From:   Dave Stevenson <dave.stevenson@...pberrypi.com>
To:     Maxime Ripard <maxime@...no.tech>
Cc:     Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        DRI Development <dri-devel@...ts.freedesktop.org>,
        Daniel Vetter <daniel.vetter@...el.com>,
        David Airlie <airlied@...ux.ie>, Eric Anholt <eric@...olt.net>,
        Nicolas Saenz Julienne <nsaenz@...nel.org>,
        bcm-kernel-feedback-list@...adcom.com,
        linux-rpi-kernel@...ts.infradead.org,
        Phil Elwell <phil@...pberrypi.com>,
        Tim Gover <tim.gover@...pberrypi.com>,
        Dom Cobley <dom@...pberrypi.com>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v4 11/12] drm/vc4: hdmi: Add a workqueue to set scrambling

Hi Maxime

Thanks for the patch.

On Fri, 7 May 2021 at 16:06, Maxime Ripard <maxime@...no.tech> wrote:
>
> It looks like some displays (like the LG 27UL850-W) don't enable the
> scrambling when the HDMI driver enables it. However, if we set later the
> scrambler enable bit, the display will work as expected.
>
> Let's create delayed work queue to periodically look at the display
> scrambling status, and if it's not set yet try to enable it again.
>
> Signed-off-by: Maxime Ripard <maxime@...no.tech>

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

> ---
>  drivers/gpu/drm/vc4/vc4_hdmi.c | 25 +++++++++++++++++++++++++
>  drivers/gpu/drm/vc4/vc4_hdmi.h |  2 ++
>  2 files changed, 27 insertions(+)
>
> diff --git a/drivers/gpu/drm/vc4/vc4_hdmi.c b/drivers/gpu/drm/vc4/vc4_hdmi.c
> index bda12fea0dce..4fa7ea419594 100644
> --- a/drivers/gpu/drm/vc4/vc4_hdmi.c
> +++ b/drivers/gpu/drm/vc4/vc4_hdmi.c
> @@ -482,6 +482,8 @@ static bool vc4_hdmi_supports_scrambling(struct drm_encoder *encoder,
>         return true;
>  }
>
> +#define SCRAMBLING_POLLING_DELAY_MS    1000
> +
>  static void vc4_hdmi_enable_scrambling(struct drm_encoder *encoder)
>  {
>         struct drm_display_mode *mode = &encoder->crtc->state->adjusted_mode;
> @@ -498,6 +500,9 @@ static void vc4_hdmi_enable_scrambling(struct drm_encoder *encoder)
>
>         HDMI_WRITE(HDMI_SCRAMBLER_CTL, HDMI_READ(HDMI_SCRAMBLER_CTL) |
>                    VC5_HDMI_SCRAMBLER_CTL_ENABLE);
> +
> +       queue_delayed_work(system_wq, &vc4_hdmi->scrambling_work,
> +                          msecs_to_jiffies(SCRAMBLING_POLLING_DELAY_MS));
>  }
>
>  static void vc4_hdmi_disable_scrambling(struct drm_encoder *encoder)
> @@ -516,6 +521,9 @@ static void vc4_hdmi_disable_scrambling(struct drm_encoder *encoder)
>         if (crtc && !vc4_hdmi_mode_needs_scrambling(&crtc->mode))
>                 return;
>
> +       if (delayed_work_pending(&vc4_hdmi->scrambling_work))
> +               cancel_delayed_work_sync(&vc4_hdmi->scrambling_work);
> +
>         HDMI_WRITE(HDMI_SCRAMBLER_CTL, HDMI_READ(HDMI_SCRAMBLER_CTL) &
>                    ~VC5_HDMI_SCRAMBLER_CTL_ENABLE);
>
> @@ -523,6 +531,22 @@ static void vc4_hdmi_disable_scrambling(struct drm_encoder *encoder)
>         drm_scdc_set_high_tmds_clock_ratio(vc4_hdmi->ddc, false);
>  }
>
> +static void vc4_hdmi_scrambling_wq(struct work_struct *work)
> +{
> +       struct vc4_hdmi *vc4_hdmi = container_of(to_delayed_work(work),
> +                                                struct vc4_hdmi,
> +                                                scrambling_work);
> +
> +       if (drm_scdc_get_scrambling_status(vc4_hdmi->ddc))
> +               return;
> +
> +       drm_scdc_set_high_tmds_clock_ratio(vc4_hdmi->ddc, true);
> +       drm_scdc_set_scrambling(vc4_hdmi->ddc, true);
> +
> +       queue_delayed_work(system_wq, &vc4_hdmi->scrambling_work,
> +                          msecs_to_jiffies(SCRAMBLING_POLLING_DELAY_MS));
> +}
> +
>  static void vc4_hdmi_encoder_post_crtc_disable(struct drm_encoder *encoder,
>                                                struct drm_atomic_state *state)
>  {
> @@ -2031,6 +2055,7 @@ static int vc4_hdmi_bind(struct device *dev, struct device *master, void *data)
>         vc4_hdmi = devm_kzalloc(dev, sizeof(*vc4_hdmi), GFP_KERNEL);
>         if (!vc4_hdmi)
>                 return -ENOMEM;
> +       INIT_DELAYED_WORK(&vc4_hdmi->scrambling_work, vc4_hdmi_scrambling_wq);
>
>         dev_set_drvdata(dev, vc4_hdmi);
>         encoder = &vc4_hdmi->encoder.base.base;
> diff --git a/drivers/gpu/drm/vc4/vc4_hdmi.h b/drivers/gpu/drm/vc4/vc4_hdmi.h
> index 3cd021136402..00efcf291c5a 100644
> --- a/drivers/gpu/drm/vc4/vc4_hdmi.h
> +++ b/drivers/gpu/drm/vc4/vc4_hdmi.h
> @@ -126,6 +126,8 @@ struct vc4_hdmi {
>         struct vc4_hdmi_encoder encoder;
>         struct drm_connector connector;
>
> +       struct delayed_work scrambling_work;
> +
>         struct i2c_adapter *ddc;
>         void __iomem *hdmicore_regs;
>         void __iomem *hd_regs;
> --
> 2.31.1
>