Am Donnerstag, 17. Juli 2025, 23:56:18 Mitteleuropäische Sommerzeit schrieb
Detlev Casanova:
> To configure audio registers, the clock of the video port in use must be
> enabled.
> As those clocks are managed by the VOP driver, they can't be enabled here
> to write the registers even when the HDMI cable is disconnected.
>
> Furthermore, the registers values are computed from the TMDS char rate,
> which is not available when disconnected.
>
> Returning -ENODEV seemed reasonable at first, but ASoC will log an error
> multiple times if dw_hdmi_qp_audio_prepare() return an error.
> Userspace might also retry multiple times, filling the kernel log with:
>
> hdmi-audio-codec hdmi-audio-codec.0.auto: ASoC error (-19): at
> snd_soc_dai_prepare() on i2s-hifi
>
> This has become even worse with the support of the second HDMI TX port.
>
> Activating the clocks to write fake data (fake because the TMDS char
> rate is unavailable) would require API changes to communicate between
> VOP and HDMI, which doesn't really make sense.
>
> Using a cached regmap to be dumped when a cable is connected won't work
> because writing order is important and some data needs to be retrieved
> from registers to write others.
>
> Returning 0 to silently fail sounds like the best and simplest solution.
>
> Signed-off-by: Detlev Casanova <detlev.casan...@collabora.com>
> ---
> drivers/gpu/drm/bridge/synopsys/dw-hdmi-qp.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/bridge/synopsys/dw-hdmi-qp.c
> b/drivers/gpu/drm/bridge/synopsys/dw-hdmi-qp.c
> index 5e5f8c2f95be1..7d3d7b5084c8d 100644
> --- a/drivers/gpu/drm/bridge/synopsys/dw-hdmi-qp.c
> +++ b/drivers/gpu/drm/bridge/synopsys/dw-hdmi-qp.c
> @@ -459,7 +459,7 @@ static int dw_hdmi_qp_audio_prepare(struct drm_connector
> *connector,
> bool ref2stream = false;
>
> if (!hdmi->tmds_char_rate)
> - return -ENODEV;
> + return 0;
nit: part of me would like a short comment stating the requirment of the
running video-clock.
Heiko
>
> if (fmt->bit_clk_provider | fmt->frame_clk_provider) {
> dev_err(hdmi->dev, "unsupported clock settings\n");
>
