On 04/07/2017 04:19 PM, Romain Perier wrote:
> Currently, the audio sampler clock is enabled from dw_hdmi_setup() at
> step E. and is kept enabled for later use. This clock should be enabled
> and disabled along with the actual audio stream and not always on (that
> is bad for PM). Futhermore, as described by the datasheet, the I2S
> variant need to gate/ungate the clock when the stream is
> enabled/disabled.
> 
> This commit adds a parameter to hdmi_audio_enable_clk() that controls
> when the audio sample clock must be enabled or disabled. Then, it adds
> the call to this function from dw_hdmi_i2s_audio_enable() and
> dw_hdmi_i2s_audio_disable().
> 
> Signed-off-by: Romain Perier <romain.per...@collabora.com>
> ---
>  drivers/gpu/drm/bridge/dw-hdmi.c | 16 +++++++++-------
>  1 file changed, 9 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/gpu/drm/bridge/dw-hdmi.c 
> b/drivers/gpu/drm/bridge/dw-hdmi.c
> index d34e0a5..3bd0807 100644
> --- a/drivers/gpu/drm/bridge/dw-hdmi.c
> +++ b/drivers/gpu/drm/bridge/dw-hdmi.c
> @@ -559,6 +559,12 @@ void dw_hdmi_set_sample_rate(struct dw_hdmi *hdmi, 
> unsigned int rate)
>  }
>  EXPORT_SYMBOL_GPL(dw_hdmi_set_sample_rate);
>  
> +static void hdmi_enable_audio_clk(struct dw_hdmi *hdmi, bool enable)
> +{
> +     hdmi_modb(hdmi, enable ? 0 : HDMI_MC_CLKDIS_AUDCLK_DISABLE,
> +               HDMI_MC_CLKDIS_AUDCLK_DISABLE, HDMI_MC_CLKDIS);
> +}
> +
>  void dw_hdmi_ahb_audio_enable(struct dw_hdmi *hdmi)
>  {
>       hdmi_set_cts_n(hdmi, hdmi->audio_cts, hdmi->audio_n);
> @@ -572,12 +578,13 @@ void dw_hdmi_ahb_audio_disable(struct dw_hdmi *hdmi)
>  void dw_hdmi_i2s_audio_enable(struct dw_hdmi *hdmi)
>  {
>       hdmi_set_cts_n(hdmi, hdmi->audio_cts, hdmi->audio_n);
> +     hdmi_enable_audio_clk(hdmi, true);
>  }
>  
>  
>  void dw_hdmi_i2s_audio_disable(struct dw_hdmi *hdmi)
>  {
> -
> +     hdmi_enable_audio_clk(hdmi, false);
>  }

I think the NULL check is still valid if you fill this function, because the IP 
also
support other modes (SPDIF and GPA).

>  
>  void dw_hdmi_audio_enable(struct dw_hdmi *hdmi)
> @@ -1365,11 +1372,6 @@ static void dw_hdmi_enable_video_path(struct dw_hdmi 
> *hdmi)
>       }
>  }
>  
> -static void hdmi_enable_audio_clk(struct dw_hdmi *hdmi)
> -{
> -     hdmi_modb(hdmi, 0, HDMI_MC_CLKDIS_AUDCLK_DISABLE, HDMI_MC_CLKDIS);
> -}
> -
>  /* Workaround to clear the overflow condition */
>  static void dw_hdmi_clear_overflow(struct dw_hdmi *hdmi)
>  {
> @@ -1471,7 +1473,7 @@ static int dw_hdmi_setup(struct dw_hdmi *hdmi, struct 
> drm_display_mode *mode)
>  
>               /* HDMI Initialization Step E - Configure audio */
>               hdmi_clk_regenerator_update_pixel_clock(hdmi);
> -             hdmi_enable_audio_clk(hdmi);
> +             hdmi_enable_audio_clk(hdmi, true);
>       }
>  
>       /* not for DVI mode */
> 

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