linux-kernel - Re: [PATCH v2 2/2] drm: dw-hdmi: gate audio clock from the I2S enablement callbacks

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Message-ID: <ad52c44d-331a-2813-6f38-7782888ab3b9@codeaurora.org>
Date:   Thu, 20 Apr 2017 15:09:36 +0530
From:   Archit Taneja <architt@...eaurora.org>
To:     Romain Perier <romain.perier@...labora.com>,
        David Airlie <airlied@...ux.ie>
Cc:     Jose Abreu <Jose.Abreu@...opsys.com>,
        Neil Armstrong <narmstrong@...libre.com>,
        Russell King <linux@...linux.org.uk>,
        dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        linux-rockchip@...ts.infradead.org,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v2 2/2] drm: dw-hdmi: gate audio clock from the I2S
 enablement callbacks



On 04/19/2017 10:21 AM, Archit Taneja wrote:
>
>
> On 04/14/2017 02:01 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
>
> s/Futhermore/Furthermore
>
>> variant need to gate/ungate the clock when the stream is
>
> s/need/needs
>
>> 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.perier@...labora.com>
>> ---
>>  drivers/gpu/drm/bridge/synopsys/dw-hdmi.c | 20 ++++++++++++++------
>>  1 file changed, 14 insertions(+), 6 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c b/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c
>> index 5b328c0..a6da634 100644
>> --- a/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c
>> +++ b/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c
>> @@ -544,6 +544,12 @@ 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);
>> @@ -557,6 +563,12 @@ 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);
>>  }
>
> This should be static too.
>
> If you're okay with the suggestions, I can fix these myself and push. Let
> me know if that's okay.

Took the liberty of going ahead with the fixes. Queued both patches to
drm-misc-next.

Thanks,
Archit

>
> Thanks,
> Archit
>
>>
>>  void dw_hdmi_audio_enable(struct dw_hdmi *hdmi)
>> @@ -1592,11 +1604,6 @@ static void dw_hdmi_enable_video_path(struct dw_hdmi *hdmi)
>>                  HDMI_MC_FLOWCTRL);
>>  }
>>
>> -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)
>>  {
>> @@ -1710,7 +1717,7 @@ 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 */
>> @@ -2438,6 +2445,7 @@ __dw_hdmi_probe(struct platform_device *pdev,
>>          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;
>>
>

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