linux-kernel - Re: [PATCH v4 6/7] drm/vc4: hdmi: Add more checks for 4k resolutions

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Date:   Wed, 26 Oct 2022 17:06:41 +0100
From:   Dave Stevenson <dave.stevenson@...pberrypi.com>
To:     maxime@...no.tech
Cc:     Daniel Vetter <daniel@...ll.ch>, Emma Anholt <emma@...olt.net>,
        Michael Turquette <mturquette@...libre.com>,
        Stephen Boyd <sboyd@...nel.org>,
        Maxime Ripard <mripard@...nel.org>,
        Ray Jui <rjui@...adcom.com>,
        Florian Fainelli <f.fainelli@...il.com>,
        David Airlie <airlied@...ux.ie>,
        Broadcom internal kernel review list 
        <bcm-kernel-feedback-list@...adcom.com>,
        Scott Branden <sbranden@...adcom.com>,
        Stefan Wahren <stefan.wahren@...e.com>,
        linux-kernel@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        Dom Cobley <popcornmix@...il.com>, linux-clk@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-rpi-kernel@...ts.infradead.org
Subject: Re: [PATCH v4 6/7] drm/vc4: hdmi: Add more checks for 4k resolutions

On Thu, 20 Oct 2022 at 10:14, <maxime@...no.tech> wrote:
>
> From: Dom Cobley <popcornmix@...il.com>
>
> At least the 4096x2160@...z mode requires some overclocking that isn't
> available by default, even if hdmi_enable_4kp60 is enabled.
>
> Let's add some logic to detect whether we can satisfy the core clock
> requirements for that mode, and prevent it from being used otherwise.
>
> Signed-off-by: Dom Cobley <popcornmix@...il.com>
> Signed-off-by: Maxime Ripard <maxime@...no.tech>

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

> ---
>  drivers/gpu/drm/vc4/vc4_drv.h  |  6 ++++++
>  drivers/gpu/drm/vc4/vc4_hdmi.c | 11 +++++++++--
>  drivers/gpu/drm/vc4/vc4_hvs.c  |  3 +++
>  3 files changed, 18 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/vc4/vc4_drv.h b/drivers/gpu/drm/vc4/vc4_drv.h
> index 8b2b1af565f9..72a6b7151d23 100644
> --- a/drivers/gpu/drm/vc4/vc4_drv.h
> +++ b/drivers/gpu/drm/vc4/vc4_drv.h
> @@ -347,6 +347,12 @@ struct vc4_hvs {
>          * available.
>          */
>         bool vc5_hdmi_enable_scrambling;
> +
> +       /*
> +        * 4096x2160@60 requires a core overclock to work, so register
> +        * whether that is sufficient.
> +        */
> +       bool vc5_hdmi_enable_4096by2160;
>  };
>
>  struct vc4_plane {
> diff --git a/drivers/gpu/drm/vc4/vc4_hdmi.c b/drivers/gpu/drm/vc4/vc4_hdmi.c
> index afe3daa2173e..fd3730ea976f 100644
> --- a/drivers/gpu/drm/vc4/vc4_hdmi.c
> +++ b/drivers/gpu/drm/vc4/vc4_hdmi.c
> @@ -1753,6 +1753,7 @@ vc4_hdmi_sink_supports_format_bpc(const struct vc4_hdmi *vc4_hdmi,
>
>  static enum drm_mode_status
>  vc4_hdmi_encoder_clock_valid(const struct vc4_hdmi *vc4_hdmi,
> +                            const struct drm_display_mode *mode,
>                              unsigned long long clock)
>  {
>         const struct drm_connector *connector = &vc4_hdmi->connector;
> @@ -1765,6 +1766,12 @@ vc4_hdmi_encoder_clock_valid(const struct vc4_hdmi *vc4_hdmi,
>         if (!vc4->hvs->vc5_hdmi_enable_scrambling && clock > HDMI_14_MAX_TMDS_CLK)
>                 return MODE_CLOCK_HIGH;
>
> +       /* 4096x2160@60 is not reliable without overclocking core */
> +       if (!vc4->hvs->vc5_hdmi_enable_4096by2160 &&
> +           mode->hdisplay > 3840 && mode->vdisplay >= 2160 &&
> +           drm_mode_vrefresh(mode) >= 50)
> +               return MODE_CLOCK_HIGH;
> +
>         if (info->max_tmds_clock && clock > (info->max_tmds_clock * 1000))
>                 return MODE_CLOCK_HIGH;
>
> @@ -1799,7 +1806,7 @@ vc4_hdmi_encoder_compute_clock(const struct vc4_hdmi *vc4_hdmi,
>         unsigned long long clock;
>
>         clock = vc4_hdmi_encoder_compute_mode_clock(mode, bpc, fmt);
> -       if (vc4_hdmi_encoder_clock_valid(vc4_hdmi, clock) != MODE_OK)
> +       if (vc4_hdmi_encoder_clock_valid(vc4_hdmi, mode, clock) != MODE_OK)
>                 return -EINVAL;
>
>         vc4_state->tmds_char_rate = clock;
> @@ -1962,7 +1969,7 @@ vc4_hdmi_encoder_mode_valid(struct drm_encoder *encoder,
>              (mode->hsync_end % 2) || (mode->htotal % 2)))
>                 return MODE_H_ILLEGAL;
>
> -       return vc4_hdmi_encoder_clock_valid(vc4_hdmi, mode->clock * 1000);
> +       return vc4_hdmi_encoder_clock_valid(vc4_hdmi, mode, mode->clock * 1000);
>  }
>
>  static const struct drm_encoder_helper_funcs vc4_hdmi_encoder_helper_funcs = {
> diff --git a/drivers/gpu/drm/vc4/vc4_hvs.c b/drivers/gpu/drm/vc4/vc4_hvs.c
> index 300ac0b57571..a68913f76687 100644
> --- a/drivers/gpu/drm/vc4/vc4_hvs.c
> +++ b/drivers/gpu/drm/vc4/vc4_hvs.c
> @@ -818,6 +818,9 @@ static int vc4_hvs_bind(struct device *dev, struct device *master, void *data)
>                 if (max_rate >= 550000000)
>                         hvs->vc5_hdmi_enable_scrambling = true;
>
> +               if (max_rate >= 600000000)
> +                       hvs->vc5_hdmi_enable_4096by2160 = true;
> +
>                 hvs->max_core_rate = max_rate;
>
>                 ret = clk_prepare_enable(hvs->core_clk);
>
> --
> b4 0.10.1