[alsa-devel] [RFC 1/6] video: hdmi: add helper function for N and CTS
Arnaud Pouliquen
arnaud.pouliquen at st.com
Tue Jan 19 14:40:31 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 | 146 +++++++++++++++++++++++++++++++++++++++++++++++++++
include/linux/hdmi.h | 11 ++++
2 files changed, 157 insertions(+)
diff --git a/drivers/video/hdmi.c b/drivers/video/hdmi.c
index 1626892..8af33c1 100644
--- a/drivers/video/hdmi.c
+++ b/drivers/video/hdmi.c
@@ -1242,3 +1242,149 @@ 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 long pixel_clk;
+ struct hdmi_audio_n_cts n_cts;
+};
+
+static const struct hdmi_audio_acr hdmi_audio_standard_acr[3][12] = {
+ { /*32 kHz*/
+ { 25175, { 4576, 28125 } }, /* 25,20/1.001 MHz */
+ { 25200, { 4096, 25200 } }, /* 25.20 MHz */
+ { 27000, { 4096, 27000 } }, /* 27.00 MHz */
+ { 27027, { 4096, 27027 } }, /* 27.00*1.001 MHz */
+ { 54000, { 4096, 54000 } }, /* 54.00 MHz */
+ { 54054, { 4096, 54054 } }, /* 54.00*1.001 MHz */
+ { 74176, { 11648, 310938 } }, /* 74.25/1.001 MHz */
+ { 74250, { 4096, 74250 } }, /* 74.25 MHz */
+ { 148352, { 11648, 421875 } }, /* 148.50/1.001 MHz */
+ { 148500, { 4096, 148500 } }, /* 148.50 MHz */
+ { 296703, { 5824, 421875 } }, /* 297/1.001 MHz */
+ { 297000, { 3072, 222750 } }, /* 297 MHz */
+ },
+ { /*44.1 kHz, 88.2 kHz 176.4 kHz*/
+ { 25175, { 7007, 31250 } }, /* 25,20/1.001 MHz */
+ { 25200, { 6272, 28000 } }, /* 25.20 MHz */
+ { 27000, { 6272, 30000 } }, /* 27.00 MHz */
+ { 27027, { 6272, 30030 } }, /* 27.00*1.001 MHz */
+ { 54000, { 6272, 60000 } }, /* 54.00 MHz */
+ { 54054, { 6272, 60060 } }, /* 54.00*1.001 MHz */
+ { 74176, { 17836, 234375 } }, /* 74.25/1.001 MHz */
+ { 74250, { 6272, 82500 } }, /* 74.25 MHz */
+ { 148352, { 8918, 234375 } }, /* 148.50/1.001 MHz */
+ { 148500, { 6272, 165000 } }, /* 148.50 MHz */
+ { 296703, { 4459, 234375 } }, /* 297/1.001 MHz */
+ { 297000, { 4704, 247500 } }, /* 297 MHz */
+ },
+ { /*48 kHz, 96 kHz 192 kHz*/
+ { 25175, { 6864, 28125 } }, /* 25,20/1.001 MHz */
+ { 25200, { 6144, 25200 } }, /* 25.20 MHz */
+ { 27000, { 6144, 27000 } }, /* 27.00 MHz */
+ { 27027, { 6144, 27027 } }, /* 27.00*1.001 MHz */
+ { 54000, { 6144, 54000 } }, /* 54.00 MHz */
+ { 54054, { 6144, 54054 } }, /* 54.00*1.001 MHz */
+ { 74176, { 11648, 140625 } }, /* 74.25/1.001 MHz */
+ { 74250, { 6144, 74250 } }, /* 74.25 MHz */
+ { 148352, { 5824, 140625 } }, /* 148.50/1.001 MHz */
+ { 148500, { 6144, 148500 } }, /* 148.50 MHz */
+ { 296703, { 5824, 281250 } }, /* 297/1.001 MHz */
+ { 297000, { 5120, 247500 } }, /* 297 MHz */
+ }
+};
+
+/**
+ * hdmi_compute_n_cts() - compute N and CTS parameters
+ * @audio_fs: audio frame clock frequency in kHz
+ * @pixel_clk: pixel clock frequency in kHz
+ * @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_compute_n_cts(unsigned int audio_fs, unsigned long pixel_clk,
+ struct hdmi_audio_n_cts *n_cts)
+{
+ int audio_freq_id, i;
+ int ratio = 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;
+ ratio = 2;
+ n_cts->n = 6272 * 2;
+ break;
+
+ case 96000:
+ audio_freq_id = HDMI_AUDIO_N_CTS_48KHZ;
+ ratio = 2;
+ n_cts->n = 6144 * 2;
+ break;
+
+ case 176400:
+ audio_freq_id = HDMI_AUDIO_N_CTS_44_1KHZ;
+ ratio = 4;
+ n_cts->n = 6272 * 4;
+ break;
+
+ case 192000:
+ audio_freq_id = HDMI_AUDIO_N_CTS_48KHZ;
+ ratio = 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 (pixel_clk == acr_table[i].pixel_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)
+ */
+ n_cts->cts = pixel_clk * n_cts->n / (128 * audio_fs);
+ } else {
+ n_cts->n = predef_n_cts->n * ratio;
+ n_cts->cts = predef_n_cts->cts;
+ }
+
+ return 0;
+}
+EXPORT_SYMBOL(hdmi_audio_compute_n_cts);
+
diff --git a/include/linux/hdmi.h b/include/linux/hdmi.h
index e974420..6508de8 100644
--- a/include/linux/hdmi.h
+++ b/include/linux/hdmi.h
@@ -333,4 +333,15 @@ 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
+ */
+struct hdmi_audio_n_cts {
+ unsigned int n;
+ unsigned int cts;
+};
+
+int hdmi_audio_compute_n_cts(unsigned int audio_fs, unsigned long pixel_clk,
+ struct hdmi_audio_n_cts *n_cts);
+
#endif /* _DRM_HDMI_H */
--
1.9.1
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