linux-kernel - Re: [PATCH v2 1/2] drm: dw-hdmi: add specific I2S and AHB functions for stream handling

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Message-ID: <18f8eac1-64c2-949e-c4e1-6c87a5e757c3@baylibre.com>
Date:   Fri, 14 Apr 2017 11:05:11 +0200
From:   Neil Armstrong <narmstrong@...libre.com>
To:     Romain Perier <romain.perier@...labora.com>,
        Archit Taneja <architt@...eaurora.org>,
        David Airlie <airlied@...ux.ie>
Cc:     dri-devel@...ts.freedesktop.org,
        linux-rockchip@...ts.infradead.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Jose Abreu <Jose.Abreu@...opsys.com>,
        Russell King <linux@...linux.org.uk>
Subject: Re: [PATCH v2 1/2] drm: dw-hdmi: add specific I2S and AHB functions
 for stream handling

On 04/14/2017 10:31 AM, 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
> 
> Signed-off-by: Romain Perier <romain.perier@...labora.com>
> ---
>  drivers/gpu/drm/bridge/synopsys/dw-hdmi.c | 26 ++++++++++++++++++++++++--
>  1 file changed, 24 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c b/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c
> index 4b6f216..5b328c0 100644
> --- a/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c
> +++ b/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c
> @@ -173,6 +173,8 @@ struct dw_hdmi {
>  
>  	unsigned int reg_shift;
>  	struct regmap *regm;
> +	void (*enable_audio)(struct dw_hdmi *hdmi);
> +	void (*disable_audio)(struct dw_hdmi *hdmi);
>  };
>  
>  #define HDMI_IH_PHY_STAT0_RX_SENSE \
> @@ -542,13 +544,29 @@ 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_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);
> +	if (hdmi->enable_audio)
> +		hdmi->enable_audio(hdmi);
>  	spin_unlock_irqrestore(&hdmi->audio_lock, flags);
>  }
>  EXPORT_SYMBOL_GPL(dw_hdmi_audio_enable);
> @@ -559,7 +577,8 @@ 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);
> +	if (hdmi->disable_audio)
> +		hdmi->disable_audio(hdmi);
>  	spin_unlock_irqrestore(&hdmi->audio_lock, flags);
>  }
>  EXPORT_SYMBOL_GPL(dw_hdmi_audio_disable);
> @@ -2404,6 +2423,8 @@ __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;
> @@ -2416,6 +2437,7 @@ __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;
>  
>  		pdevinfo.name = "dw-hdmi-i2s-audio";
>  		pdevinfo.data = &audio;
> 

Hi Romain,

Reviewed-by: Neil Armstrong <narmstrong@...libre.com>