Re: [PATCH] drm/bridge: dw-hdmi: handle ELD when DRM_BRIDGE_ATTACH_NO_CONNECTOR

[Neil Armstrong <narmstrong@baylibre.com>]

Hi drm/bridge maintainers,

On 29/10/2021 15:59, Neil Armstrong wrote:
> The current ELD handling takes the internal connector ELD buffer and
> shares it to the I2S and AHB sub-driver.
> 
> But with DRM_BRIDGE_ATTACH_NO_CONNECTOR, the connector is created
> elsewhere (not not), and an eventual connector is known only
> if the bridge chain up to a connector is enabled.
> 
> The current dw-hdmi code gets the current connector from
> atomic_enable() so use the already stored connector pointer and
> replace the buffer pointer with a callback returning the current
> connector ELD buffer.
> 
> Since a connector is not always available, either pass an empty
> ELD to the alsa HDMI driver or don't call snd_pcm_hw_constraint_eld()
> in AHB driver.
> 
> Reported-by: Martin Blumenstingl <martin.blumenstingl@googlemail.com>
> Signed-off-by: Neil Armstrong <narmstrong@baylibre.com>
> ---
>  drivers/gpu/drm/bridge/synopsys/dw-hdmi-ahb-audio.c | 10 +++++++---
>  drivers/gpu/drm/bridge/synopsys/dw-hdmi-audio.h     |  4 ++--
>  drivers/gpu/drm/bridge/synopsys/dw-hdmi-i2s-audio.c |  9 ++++++++-
>  drivers/gpu/drm/bridge/synopsys/dw-hdmi.c           | 12 ++++++++++--
>  4 files changed, 27 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/gpu/drm/bridge/synopsys/dw-hdmi-ahb-audio.c b/drivers/gpu/drm/bridge/synopsys/dw-hdmi-ahb-audio.c
> index d0db1acf11d7..7d2ed0ed2fe2 100644
> --- a/drivers/gpu/drm/bridge/synopsys/dw-hdmi-ahb-audio.c
> +++ b/drivers/gpu/drm/bridge/synopsys/dw-hdmi-ahb-audio.c
> @@ -320,13 +320,17 @@ static int dw_hdmi_open(struct snd_pcm_substream *substream)
>  	struct snd_pcm_runtime *runtime = substream->runtime;
>  	struct snd_dw_hdmi *dw = substream->private_data;
>  	void __iomem *base = dw->data.base;
> +	u8 *eld;
>  	int ret;
>  
>  	runtime->hw = dw_hdmi_hw;
>  
> -	ret = snd_pcm_hw_constraint_eld(runtime, dw->data.eld);
> -	if (ret < 0)
> -		return ret;
> +	eld = dw->data.get_eld(dw->data.hdmi);
> +	if (eld) {
> +		ret = snd_pcm_hw_constraint_eld(runtime, eld);
> +		if (ret < 0)
> +			return ret;
> +	}
>  
>  	ret = snd_pcm_limit_hw_rates(runtime);
>  	if (ret < 0)
> diff --git a/drivers/gpu/drm/bridge/synopsys/dw-hdmi-audio.h b/drivers/gpu/drm/bridge/synopsys/dw-hdmi-audio.h
> index cb07dc0da5a7..f72d27208ebe 100644
> --- a/drivers/gpu/drm/bridge/synopsys/dw-hdmi-audio.h
> +++ b/drivers/gpu/drm/bridge/synopsys/dw-hdmi-audio.h
> @@ -9,15 +9,15 @@ struct dw_hdmi_audio_data {
>  	void __iomem *base;
>  	int irq;
>  	struct dw_hdmi *hdmi;
> -	u8 *eld;
> +	u8 *(*get_eld)(struct dw_hdmi *hdmi);
>  };
>  
>  struct dw_hdmi_i2s_audio_data {
>  	struct dw_hdmi *hdmi;
> -	u8 *eld;
>  
>  	void (*write)(struct dw_hdmi *hdmi, u8 val, int offset);
>  	u8 (*read)(struct dw_hdmi *hdmi, int offset);
> +	u8 *(*get_eld)(struct dw_hdmi *hdmi);
>  };
>  
>  #endif
> 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 feb04f127b55..f50b47ac11a8 100644
> --- a/drivers/gpu/drm/bridge/synopsys/dw-hdmi-i2s-audio.c
> +++ b/drivers/gpu/drm/bridge/synopsys/dw-hdmi-i2s-audio.c
> @@ -135,8 +135,15 @@ static int dw_hdmi_i2s_get_eld(struct device *dev, void *data, uint8_t *buf,
>  			       size_t len)
>  {
>  	struct dw_hdmi_i2s_audio_data *audio = data;
> +	u8 *eld;
> +
> +	eld = audio->get_eld(audio->hdmi);
> +	if (eld)
> +		memcpy(buf, eld, min_t(size_t, MAX_ELD_BYTES, len));
> +	else
> +		/* Pass en empty ELD if connector not available */
> +		memset(buf, 0, len);
>  
> -	memcpy(buf, audio->eld, min_t(size_t, MAX_ELD_BYTES, len));
>  	return 0;
>  }
>  
> diff --git a/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c b/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c
> index 62ae63565d3a..54d8fdad395f 100644
> --- a/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c
> +++ b/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c
> @@ -757,6 +757,14 @@ static void hdmi_enable_audio_clk(struct dw_hdmi *hdmi, bool enable)
>  	hdmi_writeb(hdmi, hdmi->mc_clkdis, HDMI_MC_CLKDIS);
>  }
>  
> +static u8 *hdmi_audio_get_eld(struct dw_hdmi *hdmi)
> +{
> +	if (!hdmi->curr_conn)
> +		return NULL;
> +
> +	return hdmi->curr_conn->eld;
> +}
> +
>  static void dw_hdmi_ahb_audio_enable(struct dw_hdmi *hdmi)
>  {
>  	hdmi_set_cts_n(hdmi, hdmi->audio_cts, hdmi->audio_n);
> @@ -3432,7 +3440,7 @@ struct dw_hdmi *dw_hdmi_probe(struct platform_device *pdev,
>  		audio.base = hdmi->regs;
>  		audio.irq = irq;
>  		audio.hdmi = hdmi;
> -		audio.eld = hdmi->connector.eld;
> +		audio.get_eld = hdmi_audio_get_eld;
>  		hdmi->enable_audio = dw_hdmi_ahb_audio_enable;
>  		hdmi->disable_audio = dw_hdmi_ahb_audio_disable;
>  
> @@ -3445,7 +3453,7 @@ struct dw_hdmi *dw_hdmi_probe(struct platform_device *pdev,
>  		struct dw_hdmi_i2s_audio_data audio;
>  
>  		audio.hdmi	= hdmi;
> -		audio.eld	= hdmi->connector.eld;
> +		audio.get_eld	= hdmi_audio_get_eld;
>  		audio.write	= hdmi_writeb;
>  		audio.read	= hdmi_readb;
>  		hdmi->enable_audio = dw_hdmi_i2s_audio_enable;
> 

Is there someone who can have a look at this ?

I won't push https://lore.kernel.org/r/20211020123947.2585572-1-narmstrong@baylibre.com until this is fixed
because with DRM_BRIDGE_ATTACH_NO_CONNECTOR we loose the ELD on the HDMI sound card,

Neil