Re: [PATCH v5 13/15] drm/rockchip: dw_hdmi_qp: Support 10-bit YUV422 output format

[Daniel Stone]

Hi,

On Tue, 13 Oct 2026 at 23:52, Cristian Ciocaltea
<cristian.ciocaltea@xxxxxxxxxxxxx> wrote:
> @@ -229,7 +230,14 @@ dw_hdmi_qp_rockchip_encoder_atomic_check(struct drm_encoder *encoder,
>         }
>
>         phy_cfg.hdmi.tmds_char_rate = conn_state->hdmi.tmds_char_rate;
> -       phy_cfg.hdmi.bpc = conn_state->hdmi.output_bpc;
> +       /*
> +        * YUV422 always transmits two 12-bit components per clock cycle,
> +        * regardless of the color depth, which from a rate perspective is
> +        * equivalent to three 8-bit RGB components.  Force 8 bpc here to
> +        * keep the PHY PLL output aligned with the TMDS character rate.
> +        */
> +       phy_cfg.hdmi.bpc = (s->output_mode == ROCKCHIP_OUT_MODE_YUV422 ?
> +                               8 : conn_state->hdmi.output_bpc);

Same question as for the VOP2: why only special-case YUV422 when
YUV420 also needs special treatment? And presumably in a way which
can't just be mashed into bpc, because the maths doesn't work. So
would this be better off being handled as a separate output-mode
adjustment?

Cheers,
Daniel