Subject: [PATCH RFC 01/11] drm: bridge/dw_hdmi: clean up hdmi_set_clk_regenerator()

From: [email-masked] (Yang Kuankuan)
Date: Tue, 31 Mar 2015 02:55:53 -0400

Hi Russell,

On 03/30/2015 03:40 PM, Russell King wrote:
> Clean up hdmi_set_clk_regenerator() by allowing it to take the audio
> sample rate and ratio directly, rather than hiding it inside the
> function.  Raise the unsupported pixel clock/sample rate message from
> debug to error level as this results in audio not working correctly.
>
> Signed-off-by: Russell King <[email-masked]>
> ---
>   drivers/gpu/drm/bridge/dw_hdmi.c | 32 +++++++++++++++-----------------
>   1 file changed, 15 insertions(+), 17 deletions(-)
>
> diff --git a/drivers/gpu/drm/bridge/dw_hdmi.c b/drivers/gpu/drm/bridge/dw_hdmi.c
> index cca1c3d165e2..49df6c8c4ea8 100644
> --- a/drivers/gpu/drm/bridge/dw_hdmi.c
> +++ b/drivers/gpu/drm/bridge/dw_hdmi.c
> @@ -335,39 +335,37 @@ static unsigned int hdmi_compute_cts(unsigned int freq, unsigned long pixel_clk,
>   }
>   
>   static void hdmi_set_clk_regenerator(struct dw_hdmi *hdmi,
> -				     unsigned long pixel_clk)
> +	unsigned long pixel_clk, unsigned int sample_rate, unsigned int ratio)
>   {
> -	unsigned int clk_n, clk_cts;
> +	unsigned int n, cts;
>   
> -	clk_n = hdmi_compute_n(hdmi->sample_rate, pixel_clk,
> -			       hdmi->ratio);
> -	clk_cts = hdmi_compute_cts(hdmi->sample_rate, pixel_clk,
> -				   hdmi->ratio);
> -
> -	if (!clk_cts) {
> -		dev_dbg(hdmi->dev, "%s: pixel clock not supported: %lu\n",
> -			__func__, pixel_clk);
> -		return;
> +	n = hdmi_compute_n(sample_rate, pixel_clk, ratio);
> +	cts = hdmi_compute_cts(sample_rate, pixel_clk, ratio);
> +	if (!cts) {
> +		dev_err(hdmi->dev,
> +			"%s: pixel clock/sample rate not supported: %luMHz / %ukHz\n",
> +			__func__, pixel_clk, sample_rate);
>   	}
>   
> -	dev_dbg(hdmi->dev, "%s: samplerate=%d  ratio=%d  pixelclk=%lu  N=%d cts=%d\n",
> -		__func__, hdmi->sample_rate, hdmi->ratio,
> -		pixel_clk, clk_n, clk_cts);
> +	dev_dbg(hdmi->dev, "%s: samplerate=%ukHz ratio=%d pixelclk=%luMHz N=%d cts=%d\n",
> +		__func__, sample_rate, ratio, pixel_clk, n, cts);
>   
> -	hdmi_set_cts_n(hdmi, clk_cts, clk_n);
> +	hdmi_set_cts_n(hdmi, cts, n);
>   }
>   
>   static void hdmi_init_clk_regenerator(struct dw_hdmi *hdmi)
>   {
>   	mutex_lock(&hdmi->audio_mutex);
> -	hdmi_set_clk_regenerator(hdmi, 74250000);
> +	hdmi_set_clk_regenerator(hdmi, 74250000, hdmi->sample_rate,
> +				 hdmi->ratio);
>   	mutex_unlock(&hdmi->audio_mutex);
>   }
>   
>   static void hdmi_clk_regenerator_update_pixel_clock(struct dw_hdmi *hdmi)
>   {
>   	mutex_lock(&hdmi->audio_mutex);
> -	hdmi_set_clk_regenerator(hdmi, hdmi->hdmi_data.video_mode.mpixelclock);
> +	hdmi_set_clk_regenerator(hdmi, hdmi->hdmi_data.video_mode.mpixelclock,
> +				 hdmi->sample_rate, hdmi->ratio);

I'm okay with this change, and also I am preparing that collect N/CTS
setting to an array, like this :

     struct n_cts {
         unsigned int cts;
         unsigned int n;
     };

     struct tmds_n_cts {
         unsigned long tmds;
         /* 1 entry each for 32KHz, 44.1KHz, and 48KHz */
         struct n_cts n_cts[3];
     };

     static const struct tmds_n_cts n_cts_table[] = {
         { 25175000, {{ 28125,  4576}, { 31250,  7007}, { 25175, 6144} } },
     }

But I am confused by the "hdmi->ratio", this variable was modify to 100 
in bind
funciton, then nowhere would change it again. In this case "hdmi->ratio" 
seems
an unused variable, can we remove it ?

Best regards.
Yakir Yang

>   	mutex_unlock(&hdmi->audio_mutex);
>   }
>