linux-kernel - Re: [PATCH 01/11] drm: bridge/dw_hdmi: add audio sample channel status setting

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Date:	Sat, 31 Jan 2015 10:59:57 +0000
From:	Russell King - ARM Linux <linux@....linux.org.uk>
To:	Yakir Yang <ykk@...k-chips.com>
Cc:	David Airlie <airlied@...ux.ie>,
	Philipp Zabel <p.zabel@...gutronix.de>,
	Fabio Estevam <fabio.estevam@...escale.com>,
	Shawn Guo <shawn.guo@...aro.org>,
	Rob Clark <robdclark@...il.com>,
	Mark Yao <mark.yao@...k-chips.com>,
	Daniel Vetter <daniel@...ll.ch>,
	dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
	djkurtz@...omium.org, dbehr@...omoum.org, mmind00@...glemail.com,
	dianders@...omium.org, marcheu@...omium.org,
	rockchip-discuss@...omium.org
Subject: Re: [PATCH 01/11] drm: bridge/dw_hdmi: add audio sample channel
 status setting

On Fri, Jan 30, 2015 at 06:19:46AM -0500, Yakir Yang wrote:
> When transmitting IEC60985 linear PCM audio, we configure the
> Aduio Sample Channel Status information of all the channel
> status bits in the IEC60958 frame.

It appears that the iMX6 version of the DW-HDMI IP does not have these
registers.  These registers are quite possibly only available on IPs
which do not have the built-in AHB DMA, since the channel status bits
are encoded into the samples in memory.

Can you report what identifying information your version of this IP
outputs please?  On iMX6, I get:

dwhdmi-imx 120000.hdmi: Detected HDMI controller 0x13:0xa:0xa0:0xc1

for iMX6Quad, and for iMX6Solo:

dwhdmi-imx 120000.hdmi: Detected HDMI controller 0x13:0x1a:0xa0:0xc1

Thanks.

Further comments below.

> diff --git a/drivers/gpu/drm/bridge/dw_hdmi.c b/drivers/gpu/drm/bridge/dw_hdmi.c
> index 423addc..2ded957 100644
> --- a/drivers/gpu/drm/bridge/dw_hdmi.c
> +++ b/drivers/gpu/drm/bridge/dw_hdmi.c
> @@ -204,6 +204,47 @@ static void hdmi_regenerate_n_cts(struct dw_hdmi *hdmi, unsigned int n,
>  	hdmi_writeb(hdmi, n & 0xff, HDMI_AUD_N1);
>  }
>  
> +static void hdmi_set_schnl(struct dw_hdmi *hdmi)
> +{
> +	u8 aud_schnl_samplerate;
> +
> +	switch (hdmi->sample_rate) {
> +	case 32000:
> +		aud_schnl_samplerate = HDMI_FC_AUDSCHNLS7_SMPRATE_32K;
> +		break;
> +	case 44100:
> +		aud_schnl_samplerate = HDMI_FC_AUDSCHNLS7_SMPRATE_44K1;
> +		break;
> +	case 48000:
> +		aud_schnl_samplerate = HDMI_FC_AUDSCHNLS7_SMPRATE_48K;
> +		break;
> +	case 88200:
> +		aud_schnl_samplerate = HDMI_FC_AUDSCHNLS7_SMPRATE_88K2;
> +		break;
> +	case 96000:
> +		aud_schnl_samplerate = HDMI_FC_AUDSCHNLS7_SMPRATE_96K;
> +		break;
> +	case 176400:
> +		aud_schnl_samplerate = HDMI_FC_AUDSCHNLS7_SMPRATE_176K4;
> +		break;
> +	case 192000:
> +		aud_schnl_samplerate = HDMI_FC_AUDSCHNLS7_SMPRATE_192K;
> +		break;
> +	case 768000:
> +		aud_schnl_samplerate = HDMI_FC_AUDSCHNLS7_SMPRATE_768K;
> +		break;
> +	default:
> +		aud_schnl_samplerate = HDMI_FC_AUDSCHNLS7_SMPRATE_44K1;
> +		break;
> +	}
> +
> +	/* set channel status register */
> +	hdmi_modb(hdmi, aud_schnl_samplerate,
> +		  HDMI_FC_AUDSCHNLS7_SMPRATE_MASK, HDMI_FC_AUDSCHNLS7);
> +	hdmi_writeb(hdmi, ((~aud_schnl_samplerate) << 4) | 0x2,
> +		    HDMI_FC_AUDSCHNLS8);
> +}
> +

You should not split patches up like this - this patch introduces a new
static function, which is never used until a subsequent patch.  If this
patch were to be merged, it would introduce a new build warning.

Please ensure that each patch in the series can be applied in sequence
without causing a regression.

Thanks.

-- 
FTTC broadband for 0.8mile line: currently at 10.5Mbps down 400kbps up
according to speedtest.net.
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