Re: [PATCH v4 1/2] video: hdmi: add helper functions for N and CTS

[Arnaud Pouliquen <arnaud.pouliquen@st.com>]

Hello,

As there is no more feedback on this patch, should i suppose that I need
to abandon it?

I can integrate it in my driver... but as, N and CTS calculation is not
platform dependent, this would make sense to add it in a generic part.
(Example of another platform that could use it:
https://patchwork.kernel.org/patch/8887341)

Thanks and regards
Arnaud

On 04/28/2016 02:13 PM, Arnaud Pouliquen wrote:
> Add linux-fbdev diffusion list in loop for patch-set review.
> 
> On 04/21/2016 05:29 PM, Arnaud POULIQUEN wrote:
>> Add helper functions to compute HDMI CTS and N parameters.
>> Implementation is based on HDMI 1.4b specification.
>>
>> Signed-off-by: Arnaud Pouliquen <arnaud.pouliquen@st.com>
>> Acked-by: Benjamin Gaignard <benjamin.gaignard@linaro.org>
>> Acked-by: Vincent ABRIOU <vincent.abriou@st.com>
>> ---
>>  drivers/video/hdmi.c | 208 +++++++++++++++++++++++++++++++++++++++++++++++++++
>>  include/linux/hdmi.h |  24 ++++++
>>  2 files changed, 232 insertions(+)
>>
>> diff --git a/drivers/video/hdmi.c b/drivers/video/hdmi.c
>> index 1626892..5d124ef 100644
>> --- a/drivers/video/hdmi.c
>> +++ b/drivers/video/hdmi.c
>> @@ -1242,3 +1242,211 @@ int hdmi_infoframe_unpack(union hdmi_infoframe *frame, void *buffer)
>>  	return ret;
>>  }
>>  EXPORT_SYMBOL(hdmi_infoframe_unpack);
>> +
>> +/*
>> + * audio clock regeneration (acr) parameters
>> + * N and CTS computation are based on HDMI specification 1.4b
>> + */
>> +enum hdmi_audio_rate {
>> +	HDMI_AUDIO_N_CTS_32KHZ,
>> +	HDMI_AUDIO_N_CTS_44_1KHZ,
>> +	HDMI_AUDIO_N_CTS_48KHZ,
>> +};
>> +
>> +struct hdmi_audio_acr {
>> +	unsigned int tmds_clk;
>> +	struct hdmi_audio_n_cts n_cts;
>> +};
>> +
>> +static const struct hdmi_audio_acr hdmi_audio_standard_acr[3][13] = {
>> +	[HDMI_AUDIO_N_CTS_32KHZ] = {
>> +		/* N and CTS values for 32 kHz rate*/
>> +		{  25174825, {  4576,  28125, 0 } }, /* 25.20/1.001  MHz */
>> +		{  25200000, {  4096,  25200, 0 } }, /* 25.20        MHz */
>> +		{  27000000, {  4096,  27000, 0 } }, /* 27.00        MHz */
>> +		{  27027000, {  4096,  27027, 0 } }, /* 27.00*1.001  MHz */
>> +		{  54000000, {  4096,  54000, 0 } }, /* 54.00        MHz */
>> +		{  54054000, {  4096,  54054, 0 } }, /* 54.00*1.001  MHz */
>> +		{  74175824, { 11648, 210937, 50 } }, /* 74.25/1.001 MHz */
>> +		{  74250000, {  4096,  74250, 0 } }, /* 74.25        MHz */
>> +		{ 148351648, { 11648, 421875, 0 } }, /* 148.50/1.001 MHz */
>> +		{ 148500000, {  4096, 148500, 0 } }, /* 148.50       MHz */
>> +		{ 296703296, {  5824, 421875, 0 } }, /* 297/1.001 MHz (truncated)*/
>> +		{ 296703297, {  5824, 421875, 0 } }, /* 297/1.001 MHz (rounded)*/
>> +		{ 297000000, {  3072, 222750, 0 } }, /* 297          MHz */
>> +	},
>> +	[HDMI_AUDIO_N_CTS_44_1KHZ] = {
>> +		/* N and CTS values for 44.1 kHz, 88.2 kHz and 176.4 kHz rates*/
>> +		{  25174825, {  7007,  31250, 0 } }, /* 25.20/1.001  MHz */
>> +		{  25200000, {  6272,  28000, 0 } }, /* 25.20        MHz */
>> +		{  27000000, {  6272,  30000, 0 } }, /* 27.00        MHz */
>> +		{  27027000, {  6272,  30030, 0 } }, /* 27.00*1.001  MHz */
>> +		{  54000000, {  6272,  60000, 0 } }, /* 54.00        MHz */
>> +		{  54054000, {  6272,  60060, 0 } }, /* 54.00*1.001  MHz */
>> +		{  74175824, { 17836, 234375, 0 } }, /* 74.25/1.001  MHz */
>> +		{  74250000, {  6272,  82500, 0 } }, /* 74.25        MHz */
>> +		{ 148351648, {  8918, 234375, 0 } }, /* 148.50/1.001 MHz */
>> +		{ 148500000, {  6272, 165000, 0 } }, /* 148.50       MHz */
>> +		{ 296703296, {  4459, 234375, 0 } }, /* 297/1.001 MHz (truncated) */
>> +		{ 296703297, {  4459, 234375, 0 } }, /* 297/1.001 MHz (rounded) */
>> +		{ 297000000, {  4704, 247500, 0 } }, /* 297          MHz */
>> +	},
>> +	[HDMI_AUDIO_N_CTS_48KHZ] = {
>> +		/* N and CTS values for 48 kHz, 96 kHz and 192 kHz rates*/
>> +		{  25174825, {  6864,  28125, 0 } }, /* 25.20/1.001  MHz */
>> +		{  25200000, {  6144,  25200, 0 } }, /* 25.20        MHz */
>> +		{  27000000, {  6144,  27000, 0 } }, /* 27.00        MHz */
>> +		{  27027000, {  6144,  27027, 0 } }, /* 27.00*1.001  MHz */
>> +		{  54000000, {  6144,  54000, 0 } }, /* 54.00        MHz */
>> +		{  54054000, {  6144,  54054, 0 } }, /* 54.00*1.001  MHz */
>> +		{  74175824, { 11648, 140625, 0 } }, /* 74.25/1.001  MHz */
>> +		{  74250000, {  6144,  74250, 0 } }, /* 74.25        MHz */
>> +		{ 148351648, {  5824, 140625, 0 } }, /* 148.50/1.001 MHz */
>> +		{ 148500000, {  6144, 148500, 0 } }, /* 148.50       MHz */
>> +		{ 296703296, {  5824, 281250, 0 } }, /* 297/1.001 MHz (truncated) */
>> +		{ 296703297, {  5824, 281250, 0 } }, /* 297/1.001 MHz (rounded) */
>> +		{ 297000000, {  5120, 247500, 0 } }, /* 297          MHz */
>> +	}
>> +};
>> +
>> +/**
>> + * hdmi_audio_get_coherent_n_cts() - compute N and CTS parameters for coherent
>> + * clocks. Coherent clock means that audio and TMDS clocks have the same
>> + * source (no drifts between clocks).
>> + *
>> + * @audio_fs: audio frame clock frequency in Hz
>> + * @tmds_clk: HDMI TMDS clock frequency in Hz
>> + * @n_cts: N and CTS parameter returned to user
>> + *
>> + * Values computed are based on table described in HDMI specification 1.4b
>> + *
>> + * Returns 0 on success or a negative error code on failure.
>> + */
>> +int hdmi_audio_get_coherent_n_cts(unsigned int audio_fs,
>> +				  unsigned int tmds_clk,
>> +				  struct hdmi_audio_n_cts *n_cts)
>> +{
>> +	int audio_freq_id, i;
>> +	int rate_coeff = 1;
>> +	u64 val, min;
>> +	const struct hdmi_audio_acr  *acr_table;
>> +	const struct hdmi_audio_n_cts *predef_n_cts = NULL;
>> +
>> +	switch (audio_fs) {
>> +	case 32000:
>> +		audio_freq_id = HDMI_AUDIO_N_CTS_32KHZ;
>> +		n_cts->n = 4096;
>> +		break;
>> +	case 44100:
>> +		audio_freq_id = HDMI_AUDIO_N_CTS_44_1KHZ;
>> +		n_cts->n = 6272;
>> +		break;
>> +	case 48000:
>> +		audio_freq_id = HDMI_AUDIO_N_CTS_48KHZ;
>> +		n_cts->n = 6144;
>> +		break;
>> +	case 88200:
>> +		audio_freq_id = HDMI_AUDIO_N_CTS_44_1KHZ;
>> +		rate_coeff = 2;
>> +		n_cts->n = 6272 * 2;
>> +		break;
>> +	case 96000:
>> +		audio_freq_id = HDMI_AUDIO_N_CTS_48KHZ;
>> +		rate_coeff = 2;
>> +		n_cts->n = 6144 * 2;
>> +		break;
>> +	case 176400:
>> +		audio_freq_id = HDMI_AUDIO_N_CTS_44_1KHZ;
>> +		rate_coeff = 4;
>> +		n_cts->n = 6272 * 4;
>> +		break;
>> +	case 192000:
>> +		audio_freq_id = HDMI_AUDIO_N_CTS_48KHZ;
>> +		rate_coeff = 4;
>> +		n_cts->n = 6144 * 4;
>> +		break;
>> +	default:
>> +		return -EINVAL;
>> +	}
>> +
>> +	acr_table = hdmi_audio_standard_acr[audio_freq_id];
>> +	for (i = 0; i < ARRAY_SIZE(hdmi_audio_standard_acr[0]); i++) {
>> +		if (tmds_clk == acr_table[i].tmds_clk) {
>> +			predef_n_cts = &acr_table[i].n_cts;
>> +			n_cts->n = predef_n_cts->n * rate_coeff;
>> +			n_cts->cts = predef_n_cts->cts;
>> +			n_cts->cts_1_ratio = predef_n_cts->cts_1_ratio;
>> +			return 0;
>> +		}
>> +	}
>> +
>> +	/*
>> +	 * Pre-defined frequency not found. Compute CTS using formula:
>> +	 * CTS = (Ftdms_clk * N) / (128 * audio_fs)
>> +	 */
>> +	val = (u64)tmds_clk * n_cts->n;
>> +	n_cts->cts = div64_u64(val, 128UL * audio_fs);
>> +
>> +	n_cts->cts_1_ratio = 0;
>> +	min = (u64)n_cts->cts * 128UL * audio_fs;
>> +	if (min < val) {
>> +		/*
>> +		 * Non-accurate value for CTS
>> +		 * compute ratio, needed by user to alternate in ACR
>> +		 * between CTS and CTS + 1 value.
>> +		 */
>> +		n_cts->cts_1_ratio = ((u32)(val - min)) * 100 /
>> +				     (128 * audio_fs);
>> +	}
>> +
>> +	return 0;
>> +}
>> +EXPORT_SYMBOL(hdmi_audio_get_coherent_n_cts);
>> +
>> +/**
>> + * hdmi_audio_get_non_coherent_n() - get N parameter for non-coherent
>> + * clocks. None-coherent clocks means that audio and TMDS clocks have not the
>> + * same source (drifts between clocks). In this case assumption is that CTS is
>> + * automatically calculated by hardware.
>> + *
>> + * @audio_fs: audio frame clock frequency in Hz
>> + *
>> + * Values computed are based on table described in HDMI specification 1.4b
>> + *
>> + * Returns n value.
>> + */
>> +int hdmi_audio_get_non_coherent_n(unsigned int audio_fs)
>> +{
>> +	unsigned int n;
>> +
>> +	switch (audio_fs) {
>> +	case 32000:
>> +		n = 4096;
>> +		break;
>> +	case 44100:
>> +		n = 6272;
>> +		break;
>> +	case 48000:
>> +		n = 6144;
>> +		break;
>> +	case 88200:
>> +		n = 6272 * 2;
>> +		break;
>> +	case 96000:
>> +		n = 6144 * 2;
>> +		break;
>> +	case 176400:
>> +		n = 6272 * 4;
>> +		break;
>> +	case 192000:
>> +		n = 6144 * 4;
>> +		break;
>> +	default:
>> +		/* Not pre-defined, recommended value: 128 * fs / 1000 */
>> +		n = (audio_fs * 128) / 1000;
>> +	}
>> +
>> +	return n;
>> +}
>> +EXPORT_SYMBOL(hdmi_audio_get_non_coherent_n);
>> +
>> diff --git a/include/linux/hdmi.h b/include/linux/hdmi.h
>> index e974420..088d09f8 100644
>> --- a/include/linux/hdmi.h
>> +++ b/include/linux/hdmi.h
>> @@ -333,4 +333,28 @@ int hdmi_infoframe_unpack(union hdmi_infoframe *frame, void *buffer);
>>  void hdmi_infoframe_log(const char *level, struct device *dev,
>>  			union hdmi_infoframe *frame);
>>  
>> +/**
>> + * struct hdmi_audio_n_cts - n and cts parameter for ACR packets
>> + * @n: N parameter
>> + * @cts: CTS parameter
>> + * @cts_1_ratio: ratio from 0 to 99 to alternate "CTS" and "CTS + 1" values
>> + *  ratio = 0: CTS parameter is accurate, no need to alternate with "CTS + 1"
>> + *             value
>> + *  ratio = x: Need to alternate with ACR "CTS + 1" value x percent of the time
>> + *             to generate accurate audio clock
>> + *  as exemple: if cts_1_ratio = 30: to have an accurate value, user
>> + *  should transfer CTS value 70% of the time and (CTS+1) value 30% of the time
>> + */
>> +struct hdmi_audio_n_cts {
>> +	unsigned int n;
>> +	unsigned int cts;
>> +	unsigned int cts_1_ratio;
>> +};
>> +
>> +int hdmi_audio_get_coherent_n_cts(unsigned int audio_fs,
>> +				  unsigned int tmds_clk,
>> +				  struct hdmi_audio_n_cts *n_cts);
>> +
>> +int hdmi_audio_get_non_coherent_n(unsigned int audio_fs);
>> +
>>  #endif /* _DRM_HDMI_H */
>>