Hi Maxime!
Dne sreda, 20. september 2023 ob 16:35:22 CEST je Maxime Ripard napisal(a):
> A lot of HDMI drivers have some variation of the formula to calculate
> the TMDS character rate from a mode, but few of them actually take all
> parameters into account.
>
> Let's create a helper to provide that rate taking all parameters into
> account.
>
> Signed-off-by: Maxime Ripard <mripard@xxxxxxxxxx>
> ---
> drivers/gpu/drm/drm_connector.c | 31 +++++++++++++++++++++++++++++++
> include/drm/drm_connector.h | 5 +++++
> 2 files changed, 36 insertions(+)
>
> diff --git a/drivers/gpu/drm/drm_connector.c b/drivers/gpu/drm/drm_connector.c
> index b01cb4783ea6..4c1af97971bb 100644
> --- a/drivers/gpu/drm/drm_connector.c
> +++ b/drivers/gpu/drm/drm_connector.c
> @@ -2944,6 +2944,37 @@ void drm_connector_update_privacy_screen(const struct drm_connector_state *conne
> }
> EXPORT_SYMBOL(drm_connector_update_privacy_screen);
>
> +/**
> + * drm_connector_hdmi_compute_mode_clock() - Computes the TMDS Character Rate
> + * @mode: Display mode to compute the clock for
> + * @bpc: Bits per character
> + * @fmt: Output Pixel Format used
> + *
> + * Returns the TMDS Character Rate for a given mode, bpc count and output format.
> + *
> + * RETURNS:
> + * The TMDS Character Rate, in Hertz
> + */
> +unsigned long long
> +drm_connector_hdmi_compute_mode_clock(const struct drm_display_mode *mode,
> + unsigned int bpc,
> + enum hdmi_colorspace fmt)
> +{
> + unsigned long long clock = mode->clock * 1000ULL;
> +
> + if (mode->flags & DRM_MODE_FLAG_DBLCLK)
> + clock = clock * 2;
> +
> + if (fmt == HDMI_COLORSPACE_YUV422)
> + bpc = 8;
I think you're missing YUV420 handling, which needs half of clock speed. But
this is a thing of HDMI2.
Best regards,
Jernej
> +
> + clock = clock * bpc;
> + do_div(clock, 8);
> +
> + return clock;
> +}
> +EXPORT_SYMBOL(drm_connector_hdmi_compute_mode_clock);
> +
> int drm_connector_set_obj_prop(struct drm_mode_object *obj,
> struct drm_property *property,
> uint64_t value)
> diff --git a/include/drm/drm_connector.h b/include/drm/drm_connector.h
> index a66cb4e35d7b..d74e9c64ee88 100644
> --- a/include/drm/drm_connector.h
> +++ b/include/drm/drm_connector.h
> @@ -38,6 +38,7 @@ struct drm_connector_helper_funcs;
> struct drm_modeset_acquire_ctx;
> struct drm_device;
> struct drm_crtc;
> +struct drm_display_mode;
> struct drm_encoder;
> struct drm_panel;
> struct drm_property;
> @@ -2115,6 +2116,10 @@ void drm_connector_attach_privacy_screen_properties(struct drm_connector *conn);
> void drm_connector_attach_privacy_screen_provider(
> struct drm_connector *connector, struct drm_privacy_screen *priv);
> void drm_connector_update_privacy_screen(const struct drm_connector_state *connector_state);
> +unsigned long long
> +drm_connector_hdmi_compute_mode_clock(const struct drm_display_mode *mode,
> + unsigned int bpc,
> + enum hdmi_colorspace fmt);
>
> /**
> * struct drm_tile_group - Tile group metadata
>
>
