Re: [PATCH v2 1/2] drm/vc4: hdmi: Make sure our clock rate is within limits

From: Dave Stevenson <dave.stevenson@raspberrypi.com>
To: Maxime Ripard <maxime@cerno.tech>
Cc: Mark Rutland <mark.rutland@arm.com>,
	devicetree@vger.kernel.org, Tim Gover <tim.gover@raspberrypi.com>,
	David Airlie <airlied@linux.ie>,
	DRI Development <dri-devel@lists.freedesktop.org>,
	Rob Herring <robh+dt@kernel.org>,
	bcm-kernel-feedback-list@broadcom.com,
	linux-rpi-kernel@lists.infradead.org,
	Thomas Zimmermann <tzimmermann@suse.de>,
	Daniel Vetter <daniel.vetter@intel.com>,
	Frank Rowand <frowand.list@gmail.com>,
	Phil Elwell <phil@raspberrypi.com>,
	linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH v2 1/2] drm/vc4: hdmi: Make sure our clock rate is within limits
Date: Thu, 19 Nov 2020 11:19:27 +0000	[thread overview]
Message-ID: <CAPY8ntDdRkNBayrhJX+9Dvvbx8PsnMGTuGPxEPZ2-ULcZg2y=w@mail.gmail.com> (raw)
In-Reply-To: <20201029122522.1917579-1-maxime@cerno.tech>

Hi Maxime

On Thu, 29 Oct 2020 at 12:25, Maxime Ripard <maxime@cerno.tech> wrote:
>
> The HDMI controller cannot go above a certain pixel rate limit depending on
> the generations, but that limit is only enforced in mode_valid at the
> moment, which means that we won't advertise modes that exceed that limit,
> but the userspace is still free to try to setup a mode that would.
>
> Implement atomic_check to make sure we check it in that scenario too.
>
> Signed-off-by: Maxime Ripard <maxime@cerno.tech>

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

> ---
>
> Changes from v1:
>   - Added that patch to resolve a conflict
> ---
>  drivers/gpu/drm/vc4/vc4_hdmi.c | 15 +++++++++++++++
>  1 file changed, 15 insertions(+)
>
> diff --git a/drivers/gpu/drm/vc4/vc4_hdmi.c b/drivers/gpu/drm/vc4/vc4_hdmi.c
> index e8f99e290655..3d0338822cd2 100644
> --- a/drivers/gpu/drm/vc4/vc4_hdmi.c
> +++ b/drivers/gpu/drm/vc4/vc4_hdmi.c
> @@ -760,6 +760,20 @@ static void vc4_hdmi_encoder_enable(struct drm_encoder *encoder)
>  {
>  }
>
> +static int vc4_hdmi_encoder_atomic_check(struct drm_encoder *encoder,
> +                                        struct drm_crtc_state *crtc_state,
> +                                        struct drm_connector_state *conn_state)
> +{
> +       struct drm_display_mode *mode = &crtc_state->adjusted_mode;
> +       struct vc4_hdmi *vc4_hdmi = encoder_to_vc4_hdmi(encoder);
> +       unsigned long long pixel_rate = mode->clock * 1000;
> +
> +       if (pixel_rate > vc4_hdmi->variant->max_pixel_clock)
> +               return -EINVAL;
> +
> +       return 0;
> +}
> +
>  static enum drm_mode_status
>  vc4_hdmi_encoder_mode_valid(struct drm_encoder *encoder,
>                             const struct drm_display_mode *mode)
> @@ -773,6 +787,7 @@ vc4_hdmi_encoder_mode_valid(struct drm_encoder *encoder,
>  }
>
>  static const struct drm_encoder_helper_funcs vc4_hdmi_encoder_helper_funcs = {
> +       .atomic_check = vc4_hdmi_encoder_atomic_check,
>         .mode_valid = vc4_hdmi_encoder_mode_valid,
>         .disable = vc4_hdmi_encoder_disable,
>         .enable = vc4_hdmi_encoder_enable,
> --
> 2.26.2
>
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