Subject: Re: [PATCH v2] drm: bridge/dw_hdmi: add audio sample channel status setting

From: Russell King - ARM Linux admin <[email-masked]>
Date: Sun, 8 Sep 2019 19:37:48 +0100

On Thu, Sep 05, 2019 at 05:43:25PM +0800, Cheng-Yi Chiang wrote:
> From: Yakir Yang <[email-masked]>
> 
> When transmitting IEC60985 linear PCM audio, we configure the
> Aduio Sample Channel Status information of all the channel
> status bits in the IEC60958 frame.
> Refer to 60958-3 page 10 for frequency, original frequency, and
> wordlength setting.
> 
> This fix the issue that audio does not come out on some monitors
> (e.g. LG 22CV241)
> 
> Note that these registers are only for interfaces:
> I2S audio interface, General Purpose Audio (GPA), or AHB audio DMA
> (AHBAUDDMA).
> For S/PDIF interface this information comes from the stream.
> 
> Currently this function dw_hdmi_set_channel_status is only called
> from dw-hdmi-i2s-audio in I2S setup.
> 
> Signed-off-by: Yakir Yang <[email-masked]>
> Signed-off-by: Cheng-Yi Chiang <[email-masked]>
> ---
>  Original patch by Yakir Yang is at
> 
>  https://lore.kernel.org/patchwork/patch/539653/
> 
>  Change from v1 to v2:
>  1. Remove the version check because this will only be called by
>     dw-hdmi-i2s-audio, and the registers are available in I2S setup.
>  2. Set these registers in dw_hdmi_i2s_hw_params.
>  3. Fix the sample width setting so it can use 16 or 24 bits.
> 
>  .../drm/bridge/synopsys/dw-hdmi-i2s-audio.c   |  1 +
>  drivers/gpu/drm/bridge/synopsys/dw-hdmi.c     | 70 +++++++++++++++++++
>  drivers/gpu/drm/bridge/synopsys/dw-hdmi.h     | 20 ++++++
>  include/drm/bridge/dw_hdmi.h                  |  2 +
>  4 files changed, 93 insertions(+)
> 
> diff --git a/drivers/gpu/drm/bridge/synopsys/dw-hdmi-i2s-audio.c b/drivers/gpu/drm/bridge/synopsys/dw-hdmi-i2s-audio.c
> index 34d8e837555f..b801a28b0f17 100644
> --- a/drivers/gpu/drm/bridge/synopsys/dw-hdmi-i2s-audio.c
> +++ b/drivers/gpu/drm/bridge/synopsys/dw-hdmi-i2s-audio.c
> @@ -102,6 +102,7 @@ static int dw_hdmi_i2s_hw_params(struct device *dev, void *data,
>  	}
>  
>  	dw_hdmi_set_sample_rate(hdmi, hparms->sample_rate);
> +	dw_hdmi_set_channel_status(hdmi, hparms->sample_width);
>  	dw_hdmi_set_channel_count(hdmi, hparms->channels);
>  	dw_hdmi_set_channel_allocation(hdmi, hparms->cea.channel_allocation);
>  

dw_hdmi_i2s_hw_params() is passed the channel status data in
hparams->iec.status  Rather than re-creating it afresh in the driver,
I'd recommend programming the already supplied channel status data
into the registers.

> diff --git a/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c b/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c
> index bd65d0479683..d1daa369c8ae 100644
> --- a/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c
> +++ b/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c
> @@ -582,6 +582,76 @@ static unsigned int hdmi_compute_n(unsigned int freq, unsigned long pixel_clk)
>  	return n;
>  }
>  
> +/*
> + * When transmitting IEC60958 linear PCM audio, these registers allow to
> + * configure the channel status information of all the channel status
> + * bits in the IEC60958 frame. For the moment this configuration is only
> + * used when the I2S audio interface, General Purpose Audio (GPA),
> + * or AHB audio DMA (AHBAUDDMA) interface is active
> + * (for S/PDIF interface this information comes from the stream).
> + */
> +void dw_hdmi_set_channel_status(struct dw_hdmi *hdmi,
> +				unsigned int sample_width)
> +{
> +	u8 aud_schnl_samplerate;
> +	u8 aud_schnl_8;
> +	u8 word_length_bits;
> +
> +	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:
> +		dev_warn(hdmi->dev, "Unsupported audio sample rate (%u)\n",
> +			 hdmi->sample_rate);
> +		return;
> +	}
> +
> +	/* set channel status register */
> +	hdmi_modb(hdmi, aud_schnl_samplerate, HDMI_FC_AUDSCHNLS7_SMPRATE_MASK,
> +		  HDMI_FC_AUDSCHNLS7);
> +
> +	/*
> +	 * Set original frequency to be the same as frequency.
> +	 * Use one-complement value as stated in IEC60958-3 page 13.
> +	 */
> +	aud_schnl_8 = (~aud_schnl_samplerate) <<
> +			HDMI_FC_AUDSCHNLS8_ORIGSAMPFREQ_OFFSET;
> +
> +	/*
> +	 * Refer to IEC60958-3 page 12. We can accept 16 bits or 24 bits.
> +	 * Otherwise, set the register to 0t o indicate using default value.
> +	 */
> +	word_length_bits = (sample_width == 16) ? 0x2 :
> +			    ((sample_width == 24) ? 0xb : 0);
> +
> +	aud_schnl_8 |= word_length_bits << HDMI_FC_AUDSCHNLS8_WORDLEGNTH_OFFSET;
> +
> +	hdmi_writeb(hdmi, aud_schnl_8, HDMI_FC_AUDSCHNLS8);
> +}
> +EXPORT_SYMBOL_GPL(dw_hdmi_set_channel_status);

As mentioned above, the channel status data is actually already
provided - so we don't really need the above at all.  It just
needs the data programmed into the registers.

> +
>  static void hdmi_set_clk_regenerator(struct dw_hdmi *hdmi,
>  	unsigned long pixel_clk, unsigned int sample_rate)
>  {
> diff --git a/drivers/gpu/drm/bridge/synopsys/dw-hdmi.h b/drivers/gpu/drm/bridge/synopsys/dw-hdmi.h
> index 6988f12d89d9..619ebc1c8354 100644
> --- a/drivers/gpu/drm/bridge/synopsys/dw-hdmi.h
> +++ b/drivers/gpu/drm/bridge/synopsys/dw-hdmi.h
> @@ -158,6 +158,17 @@
>  #define HDMI_FC_SPDDEVICEINF                    0x1062
>  #define HDMI_FC_AUDSCONF                        0x1063
>  #define HDMI_FC_AUDSSTAT                        0x1064
> +#define HDMI_FC_AUDSV                           0x1065
> +#define HDMI_FC_AUDSU                           0x1066
> +#define HDMI_FC_AUDSCHNLS0                      0x1067
> +#define HDMI_FC_AUDSCHNLS1                      0x1068
> +#define HDMI_FC_AUDSCHNLS2                      0x1069
> +#define HDMI_FC_AUDSCHNLS3                      0x106a
> +#define HDMI_FC_AUDSCHNLS4                      0x106b
> +#define HDMI_FC_AUDSCHNLS5                      0x106c
> +#define HDMI_FC_AUDSCHNLS6                      0x106d
> +#define HDMI_FC_AUDSCHNLS7                      0x106e
> +#define HDMI_FC_AUDSCHNLS8                      0x106f
>  #define HDMI_FC_DATACH0FILL                     0x1070
>  #define HDMI_FC_DATACH1FILL                     0x1071
>  #define HDMI_FC_DATACH2FILL                     0x1072
> @@ -706,6 +717,15 @@ enum {
>  /* HDMI_FC_AUDSCHNLS7 field values */
>  	HDMI_FC_AUDSCHNLS7_ACCURACY_OFFSET = 4,
>  	HDMI_FC_AUDSCHNLS7_ACCURACY_MASK = 0x30,
> +	HDMI_FC_AUDSCHNLS7_SMPRATE_MASK = 0x0f,
> +	HDMI_FC_AUDSCHNLS7_SMPRATE_192K = 0xe,
> +	HDMI_FC_AUDSCHNLS7_SMPRATE_176K4 = 0xc,
> +	HDMI_FC_AUDSCHNLS7_SMPRATE_96K = 0xa,
> +	HDMI_FC_AUDSCHNLS7_SMPRATE_768K = 0x9,
> +	HDMI_FC_AUDSCHNLS7_SMPRATE_88K2 = 0x8,
> +	HDMI_FC_AUDSCHNLS7_SMPRATE_32K = 0x3,
> +	HDMI_FC_AUDSCHNLS7_SMPRATE_48K = 0x2,
> +	HDMI_FC_AUDSCHNLS7_SMPRATE_44K1 = 0x0,

These look very much like the IEC958_AES* consumer definitions in
include/sound/asoundef.h.

>  /* HDMI_FC_AUDSCHNLS8 field values */
>  	HDMI_FC_AUDSCHNLS8_ORIGSAMPFREQ_MASK = 0xf0,
> diff --git a/include/drm/bridge/dw_hdmi.h b/include/drm/bridge/dw_hdmi.h
> index cf528c289857..12144d2f80f4 100644
> --- a/include/drm/bridge/dw_hdmi.h
> +++ b/include/drm/bridge/dw_hdmi.h
> @@ -156,6 +156,8 @@ void dw_hdmi_setup_rx_sense(struct dw_hdmi *hdmi, bool hpd, bool rx_sense);
>  
>  void dw_hdmi_set_sample_rate(struct dw_hdmi *hdmi, unsigned int rate);
>  void dw_hdmi_set_channel_count(struct dw_hdmi *hdmi, unsigned int cnt);
> +void dw_hdmi_set_channel_status(struct dw_hdmi *hdmi,
> +				unsigned int sample_width);
>  void dw_hdmi_set_channel_allocation(struct dw_hdmi *hdmi, unsigned int ca);
>  void dw_hdmi_audio_enable(struct dw_hdmi *hdmi);
>  void dw_hdmi_audio_disable(struct dw_hdmi *hdmi);
> -- 
> 2.23.0.187.g17f5b7556c-goog
> 
> 
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