[alsa-devel] [RFC v2 1/6] video: hdmi: add helper function for N and CTS
Arnaud Pouliquen
arnaud.pouliquen at st.com
Fri Jan 22 18:48:27 CET 2016
From: Moise Gergaud <moise.gergaud at st.com>
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 at st.com>
---
drivers/video/hdmi.c | 222 +++++++++++++++++++++++++++++++++++++++++++++++++++
include/linux/hdmi.h | 22 +++++
2 files changed, 244 insertions(+)
diff --git a/drivers/video/hdmi.c b/drivers/video/hdmi.c
index 1626892..be8b8ed 100644
--- a/drivers/video/hdmi.c
+++ b/drivers/video/hdmi.c
@@ -1242,3 +1242,225 @@ 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*/
+ { 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 */
+ { 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;
+ 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;
+ break;
+ }
+ }
+
+ if (!predef_n_cts) {
+ /*
+ * predefined frequency not found. Compute CTS using formula:
+ * CTS = (Ftdms_clk * N) / (128* audio_fs)
+ */
+ uint64_t val, min;
+
+ val = (uint64_t)tmds_clk * n_cts->n;
+
+ n_cts->cts = div64_u64(val, 128UL * audio_fs);
+ min = (uint64_t)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 = ((int32_t)(val - min)) * 100 /
+ (128 * audio_fs);
+ n_cts->cts_1_ratio = 100 - n_cts->cts_1_ratio;
+ } else {
+ n_cts->cts_1_ratio = 0;
+ }
+ } else {
+ 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;
+}
+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..bf5c136 100644
--- a/include/linux/hdmi.h
+++ b/include/linux/hdmi.h
@@ -333,4 +333,26 @@ 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 in ACR "CTS + 1" value x% of the time to
+ * generate accurate audio clock
+ */
+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 */
--
1.9.1
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