linux-kernel - Re: [PATCH 3/3] drm/bridge: sii902x: make audio mclk optional

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Message-ID: <beef9917-1e8b-1ddb-740b-5b2ca8cd379c@samsung.com>
Date:   Fri, 12 Jul 2019 12:45:46 +0200
From:   Andrzej Hajda <a.hajda@...sung.com>
To:     Olivier Moysan <olivier.moysan@...com>, narmstrong@...libre.com,
        Laurent.pinchart@...asonboard.com, jonas@...boo.se,
        jernej.skrabec@...l.net, airlied@...ux.ie, daniel@...ll.ch,
        dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        benjamin.gaignard@...com, alexandre.torgue@...com,
        linux-arm-kernel@...ts.infradead.org,
        linux-stm32@...md-mailman.stormreply.com, jsarha@...com,
        robh+dt@...nel.org, mark.rutland@....com,
        devicetree@...r.kernel.org
Subject: Re: [PATCH 3/3] drm/bridge: sii902x: make audio mclk optional

On 02.07.2019 17:47, Olivier Moysan wrote:
> The master clock on i2s bus is not mandatory,
> as sii902X internal PLL can be used instead.
> Make use of mclk optional.
>
> Fixes: ff5781634c41 ("drm/bridge: sii902x: Implement HDMI audio support")
>
> Signed-off-by: Olivier Moysan <olivier.moysan@...com>
> ---
>  drivers/gpu/drm/bridge/sii902x.c | 39 +++++++++++++++++++++++----------------
>  1 file changed, 23 insertions(+), 16 deletions(-)
>
> diff --git a/drivers/gpu/drm/bridge/sii902x.c b/drivers/gpu/drm/bridge/sii902x.c
> index 36acc256e67e..a08bd9fdc046 100644
> --- a/drivers/gpu/drm/bridge/sii902x.c
> +++ b/drivers/gpu/drm/bridge/sii902x.c
> @@ -562,19 +562,21 @@ static int sii902x_audio_hw_params(struct device *dev, void *data,
>  		}
>  	}
>  
> -	ret = clk_prepare_enable(sii902x->audio.mclk);
> -	if (ret) {
> -		dev_err(dev, "Enabling mclk failed: %d\n", ret);
> -		return ret;
> -	}
> +	if (sii902x->audio.mclk) {
> +		ret = clk_prepare_enable(sii902x->audio.mclk);
> +		if (ret) {
> +			dev_err(dev, "Enabling mclk failed: %d\n", ret);
> +			return ret;
> +		}
>  
> -	mclk_rate = clk_get_rate(sii902x->audio.mclk);
> +		mclk_rate = clk_get_rate(sii902x->audio.mclk);
>  
> -	ret = sii902x_select_mclk_div(&i2s_config_reg, params->sample_rate,
> -				      mclk_rate);
> -	if (mclk_rate != ret * params->sample_rate)
> -		dev_dbg(dev, "Inaccurate reference clock (%ld/%d != %u)\n",
> -			mclk_rate, ret, params->sample_rate);
> +		ret = sii902x_select_mclk_div(&i2s_config_reg,
> +					      params->sample_rate, mclk_rate);
> +		if (mclk_rate != ret * params->sample_rate)
> +			dev_dbg(dev, "Inaccurate reference clock (%ld/%d != %u)\n",
> +				mclk_rate, ret, params->sample_rate);
> +	}
>  
>  	mutex_lock(&sii902x->mutex);
>  
> @@ -640,7 +642,8 @@ static int sii902x_audio_hw_params(struct device *dev, void *data,
>  	mutex_unlock(&sii902x->mutex);
>  
>  	if (ret) {
> -		clk_disable_unprepare(sii902x->audio.mclk);
> +		if (sii902x->audio.mclk)
> +			clk_disable_unprepare(sii902x->audio.mclk);


"if" clause is not necessary


>  		dev_err(dev, "%s: hdmi audio enable failed: %d\n", __func__,
>  			ret);
>  	}
> @@ -659,7 +662,8 @@ static void sii902x_audio_shutdown(struct device *dev, void *data)
>  
>  	mutex_unlock(&sii902x->mutex);
>  
> -	clk_disable_unprepare(sii902x->audio.mclk);
> +	if (sii902x->audio.mclk)

ditto

> +		clk_disable_unprepare(sii902x->audio.mclk);
>  }
>  
>  int sii902x_audio_digital_mute(struct device *dev, void *data, bool enable)
> @@ -752,9 +756,12 @@ static int sii902x_audio_codec_init(struct sii902x *sii902x,
>  
>  	sii902x->audio.mclk = devm_clk_get(dev, "mclk");
>  	if (IS_ERR(sii902x->audio.mclk)) {
> -		dev_err(dev, "%s: No clock (audio mclk) found: %ld\n",
> -			__func__, PTR_ERR(sii902x->audio.mclk));
> -		return 0;
> +		if (PTR_ERR(sii902x->audio.mclk) != -ENOENT) {
> +			dev_err(dev, "%s: No clock (audio mclk) found: %ld\n",
> +				__func__, PTR_ERR(sii902x->audio.mclk));
> +			return PTR_ERR(sii902x->audio.mclk);
> +		}
> +		sii902x->audio.mclk = NULL;


devm_clk_get_optional should be used here.

Summarizing, clk framework supports NULL clocks so you can adjust code
to benefit from it: no need to checks "if (sii902x->audio.mclk)". The
only place you should care is near clk_get_rate, for null clock it will
return 0, so you should react appropriately.

With that changed:

Reviewed-by: Andrzej Hajda <a.hajda@...sung.com>

 --
Regards
Andrzej


>  	}
>  
>  	sii902x->audio.pdev = platform_device_register_data(