[alsa-devel] [PATCH] drm: dw-hdmi-i2s: enable audio clock in audio_startup

[Jonas Karlman]

On 2019-08-29 06:29, Cheng-Yi Chiang wrote:
> In the designware databook, the sequence of enabling audio clock and
> setting format is not clearly specified.
> Currently, audio clock is enabled in the end of hw_param ops after
> setting format.
>
> On some monitors, there is a possibility that audio does not come out.
> Fix this by enabling audio clock in audio_startup ops
> before hw_param ops setting format.
>
> Signed-off-by: Cheng-Yi Chiang <cychiang at chromium.org>
> ---
>  drivers/gpu/drm/bridge/synopsys/dw-hdmi-i2s-audio.c | 9 +++++++++
>  1 file changed, 9 insertions(+)
>
> diff --git a/drivers/gpu/drm/bridge/synopsys/dw-hdmi-i2s-audio.c b/drivers/gpu/drm/bridge/synopsys/dw-hdmi-i2s-audio.c
> index 5cbb71a866d5..08b4adbb1ddc 100644
> --- a/drivers/gpu/drm/bridge/synopsys/dw-hdmi-i2s-audio.c
> +++ b/drivers/gpu/drm/bridge/synopsys/dw-hdmi-i2s-audio.c
> @@ -69,6 +69,14 @@ static int dw_hdmi_i2s_hw_params(struct device *dev, void *data,
>  	hdmi_write(audio, conf0, HDMI_AUD_CONF0);
>  	hdmi_write(audio, conf1, HDMI_AUD_CONF1);
>  
> +	return 0;
> +}
> +
> +static int dw_hdmi_i2s_audio_startup(struct device *dev, void *data)
> +{
> +	struct dw_hdmi_i2s_audio_data *audio = data;
> +	struct dw_hdmi *hdmi = audio->hdmi;
> +
>  	dw_hdmi_audio_enable(hdmi);
>  
>  	return 0;
> @@ -105,6 +113,7 @@ static int dw_hdmi_i2s_get_dai_id(struct snd_soc_component *component,
>  }
>  
>  static struct hdmi_codec_ops dw_hdmi_i2s_ops = {
> +	.audio_startup = dw_hdmi_i2s_audio_startup,

A small white space nit, there should be a tab and not space to align the equal sign above.
Also this patch do not cleanly apply to drm-misc-next or linux-next after
fc1ca6e01d0a "drm/bridge: dw-hdmi-i2s: add .get_eld support" was merged.

This patch does fix an issue I have observed on my Rockchip devices where audio would not always
came out after switching between audio streams having different rate and channels parameters.
I used to carry [1] to fix that issue, but this seems like a more sane fix.

[1] https://github.com/Kwiboo/linux-rockchip/commit/4862e4044532b8b480fa3a0faddc197586623808

With above fixed,

Reviewed-by: Jonas Karlman <jonas at kwiboo.se>

Regards,
Jonas

>  	.hw_params	= dw_hdmi_i2s_hw_params,
>  	.audio_shutdown	= dw_hdmi_i2s_audio_shutdown,
>  	.get_dai_id	= dw_hdmi_i2s_get_dai_id,