Subject: Re: [PATCH 1/2] drm: dw-hdmi: add specific I2S and AHB functions for
 stream handling
To: Romain Perier <romain.perier@collabora.com>,
        Archit Taneja <architt@codeaurora.org>,
        David Airlie <airlied@linux.ie>
References: <20170407141905.14147-1-romain.perier@collabora.com>
 <20170407141905.14147-2-romain.perier@collabora.com>
Cc: dri-devel@lists.freedesktop.org, linux-rockchip@lists.infradead.org,
        linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org,
        Jose Abreu <Jose.Abreu@synopsys.com>,
        Russell King <linux@armlinux.org.uk>
From: Neil Armstrong <narmstrong@baylibre.com>
Organization: Baylibre
Message-ID: <a5f10dd7-c257-07c5-3bf4-f19f43eeb548@baylibre.com>
Date: Fri, 7 Apr 2017 16:22:13 +0200
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On 04/07/2017 04:19 PM, Romain Perier wrote:
> Currently, CTS+N is forced to zero as a workaround of the IP block for
> i.MX platforms. This is requested in the datasheet of the corresponding
> IP for AHB mode only. However, we have seen that it introduces glitches
> or delays when playing a sound on HDMI for I2S mode. This proves that we
> cannot keep the current functions for handling audio stream as-is if
> these contain workaround that are specific to a mode.
> 
> This commit introduces two callbacks, one for each variant.
> dw_hdmi_setup defines the right function depending on the detected
> variant. Then, the exported functions dw_hdmi_audio_enable and
> dw_hdmi_audio_disable calls the corresponding callbacks

Thanks for the patch, I'll test it on the Amlogic platform.

> 
> Signed-off-by: Romain Perier <romain.perier@collabora.com>
> ---
>  drivers/gpu/drm/bridge/dw-hdmi.c | 31 +++++++++++++++++++++++++++++--
>  1 file changed, 29 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/bridge/dw-hdmi.c b/drivers/gpu/drm/bridge/dw-hdmi.c
> index 542d198..d34e0a5 100644
> --- a/drivers/gpu/drm/bridge/dw-hdmi.c
> +++ b/drivers/gpu/drm/bridge/dw-hdmi.c
> @@ -166,6 +166,8 @@ struct dw_hdmi {
>  
>  	void (*write)(struct dw_hdmi *hdmi, u8 val, int offset);
>  	u8 (*read)(struct dw_hdmi *hdmi, int offset);
> +	void (*enable_audio)(struct dw_hdmi *hdmi);
> +	void (*disable_audio)(struct dw_hdmi *hdmi);
>  };
>  
>  #define HDMI_IH_PHY_STAT0_RX_SENSE \
> @@ -557,13 +559,34 @@ void dw_hdmi_set_sample_rate(struct dw_hdmi *hdmi, unsigned int rate)
>  }
>  EXPORT_SYMBOL_GPL(dw_hdmi_set_sample_rate);
>  
> +void dw_hdmi_ahb_audio_enable(struct dw_hdmi *hdmi)
> +{
> +	hdmi_set_cts_n(hdmi, hdmi->audio_cts, hdmi->audio_n);
> +}
> +
> +void dw_hdmi_ahb_audio_disable(struct dw_hdmi *hdmi)
> +{
> +	hdmi_set_cts_n(hdmi, hdmi->audio_cts, 0);
> +}
> +
> +void dw_hdmi_i2s_audio_enable(struct dw_hdmi *hdmi)
> +{
> +	hdmi_set_cts_n(hdmi, hdmi->audio_cts, hdmi->audio_n);
> +}
> +
> +
> +void dw_hdmi_i2s_audio_disable(struct dw_hdmi *hdmi)
> +{
> +
> +}

For this one, it would be better to set it to NULL then check for NULL...

> +
>  void dw_hdmi_audio_enable(struct dw_hdmi *hdmi)
>  {
>  	unsigned long flags;
>  
>  	spin_lock_irqsave(&hdmi->audio_lock, flags);
>  	hdmi->audio_enable = true;
> -	hdmi_set_cts_n(hdmi, hdmi->audio_cts, hdmi->audio_n);
> +	hdmi->enable_audio(hdmi);

if (hdmi->enable_audio)
	hdmi->enable_audio(hdmi);

for consistency...

>  	spin_unlock_irqrestore(&hdmi->audio_lock, flags);
>  }
>  EXPORT_SYMBOL_GPL(dw_hdmi_audio_enable);
> @@ -574,7 +597,7 @@ void dw_hdmi_audio_disable(struct dw_hdmi *hdmi)
>  
>  	spin_lock_irqsave(&hdmi->audio_lock, flags);
>  	hdmi->audio_enable = false;
> -	hdmi_set_cts_n(hdmi, hdmi->audio_cts, 0);
> +	hdmi->disable_audio(hdmi);

if (hdmi->disable_audio)
	hdmi->disable_audio(hdmi);

>  	spin_unlock_irqrestore(&hdmi->audio_lock, flags);
>  }
>  EXPORT_SYMBOL_GPL(dw_hdmi_audio_disable);
> @@ -2114,6 +2137,8 @@ __dw_hdmi_probe(struct platform_device *pdev,
>  		audio.irq = irq;
>  		audio.hdmi = hdmi;
>  		audio.eld = hdmi->connector.eld;
> +		hdmi->enable_audio = dw_hdmi_ahb_audio_enable;
> +		hdmi->disable_audio = dw_hdmi_ahb_audio_disable;
>  
>  		pdevinfo.name = "dw-hdmi-ahb-audio";
>  		pdevinfo.data = &audio;
> @@ -2126,6 +2151,8 @@ __dw_hdmi_probe(struct platform_device *pdev,
>  		audio.hdmi	= hdmi;
>  		audio.write	= hdmi_writeb;
>  		audio.read	= hdmi_readb;
> +		hdmi->enable_audio = dw_hdmi_i2s_audio_enable;
> +		hdmi->disable_audio = dw_hdmi_i2s_audio_disable;
>  
>  		pdevinfo.name = "dw-hdmi-i2s-audio";
>  		pdevinfo.data = &audio;
>