On 04/21/2016 02:39 PM, Philipp Zabel wrote:
Hi Arnaud,
Am Donnerstag, den 21.04.2016, 10:07 +0200 schrieb Arnaud Pouliquen:
Add helper function 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
Reviewed-by: Philipp Zabel p.zabel@pengutronix.de
drivers/video/hdmi.c | 202 +++++++++++++++++++++++++++++++++++++++++++++++++++ include/linux/hdmi.h | 22 ++++++ 2 files changed, 224 insertions(+)
diff --git a/drivers/video/hdmi.c b/drivers/video/hdmi.c index 1626892..6381ce0 100644 --- a/drivers/video/hdmi.c +++ b/drivers/video/hdmi.c @@ -1242,3 +1242,205 @@ 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 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][12] = {
- { /*32 kHz*/
If you used
[HDMI_AUDIO_N_CTS_32KHZ] = {
instead, that would mirror how the array is indexed via audio_freq_id in hdmi_audio_get_coherent_n_cts below.
{ 25174825, { 4576, 28125, 0 } }, /* 25,20/1.001 MHz */^s/,/./
{ 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 */^Maybe add a comment above that tmds_clk is rounded down?
My apologize, I have forgotten to add 296703297 value to take into account truncated and rounded values as discussed in V2: { 296703296, { 5824, 421875, 0 } }, /* 297/1.001 MHz (truncated) */ { 296703297, { 5824, 421875, 0 } }, /* 297/1.001 MHz (rounded) */
{ 297000000, { 3072, 222750, 0 } }, /* 297 MHz */- },
- { /*44.1 kHz, 88.2 kHz 176.4 kHz*/
{ 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 */{ 297000000, { 4704, 247500, 0 } }, /* 297 MHz */- },
- { /*48 kHz, 96 kHz 192 kHz*/
{ 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 */{ 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;}- }
- /*
- predefined frequency not found. Compute CTS using formula:
^
- CTS = (Ftdms_clk * N) / (128* audio_fs)
^ ^
- */
^Missing spaces.
- 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)) {
^ ^These parentheses are not needed.
/** non-accurate value for CTS^
* compute ratio, needed by user to alternate in ACR^
* between CTS and CTS + 1 value.^
*/^Missing spaces.
n_cts->cts_1_ratio = 100 - ((u32)(val - min)) * 100 /(128 * audio_fs);I don't understand the purpose of the (100-x) above (and how cts_1_ratio is supposed to be used).
When for example val == (min + 0.3 * 128 * audio_fs) then cts_1_ratio = 70. To achieve an average CTS of (val), shouldn't (min) be used 70% of the time and (min+1) be used 30% of the time? I would have expected (cts_1_ratio == 30) in that case.
you are right! my reasoning is foolish... Thank for pointing this error!
+/**
- 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% of the time to
generate accurate audio clockDoes this mean that at cts_1_ratio == 30, CTS should be used 70% of the time, and CTS+1 should be used 30% of the time, or the other way around?
yes CTS should be used 70% of the time, i will add example in comment
- */
+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 */
regards Philipp
thanks and Regards Arnaud