From d46288cf0b5fa5313bf373d0fa4cee6a05310fc4 Mon Sep 17 00:00:00 2001
From: Yakir Yang <ykk@rock-chips.com>
Date: Wed, 2 Dec 2015 17:50:56 +0800
Subject: [PATCH] CHROMIUM: drm: bridge/dw_hdmi: improved the hdmi audio N/CTS
cacluate math
The original math would bring some inaccurate to N/CTS that would
caused those magic number won't fit the HDMI 1.4 Spec request:
128 * SampleRate = Tmds * N / CTS;
So this time we try to improved to math of N that would find the
minimal inaccurate with the HDMI 1.4 Spec.
Change-Id: Ied3cde3c352d955ae6f15d5e7fb172e92316c2a5
Signed-off-by: Yakir Yang <ykk@rock-chips.com>
Reviewed-on: https://chromium-review.googlesource.com/315424
Reviewed-by: Douglas Anderson <dianders@chromium.org>
---
drivers/gpu/drm/bridge/dw-hdmi.c | 201 ++++++++++++++++++++++++-------
include/drm/bridge/dw_hdmi.h | 8 ++
2 files changed, 165 insertions(+), 44 deletions(-)
diff --git a/drivers/gpu/drm/bridge/dw-hdmi.c b/drivers/gpu/drm/bridge/dw-hdmi.c
index 641d94725970..c28eb33adf1c 100644
--- a/drivers/gpu/drm/bridge/dw-hdmi.c
+++ b/drivers/gpu/drm/bridge/dw-hdmi.c
@@ -53,6 +53,62 @@ enum hdmi_datamap {
YCbCr422_12B = 0x12,
};
+/*
+ * Unless otherwise noted, entries in this table are 100% optimization.
+ * Values can be obtained from hdmi_compute_n() but that function is
+ * slow so we pre-compute values we expect to see.
+ *
+ * All 32k and 48k values are expected to be the same (due to the way
+ * the math works) for any rate that's an exact kHz.
+ */
+static const struct dw_hdmi_audio_tmds_n common_tmds_n_table[] = {
+ { .tmds = 25175000, .n_32k = 4096, .n_44k1 = 12854, .n_48k = 6144, },
+ { .tmds = 25200000, .n_32k = 4096, .n_44k1 = 5656, .n_48k = 6144, },
+ { .tmds = 27000000, .n_32k = 4096, .n_44k1 = 5488, .n_48k = 6144, },
+ { .tmds = 28320000, .n_32k = 4096, .n_44k1 = 5586, .n_48k = 6144, },
+ { .tmds = 30240000, .n_32k = 4096, .n_44k1 = 5642, .n_48k = 6144, },
+ { .tmds = 31500000, .n_32k = 4096, .n_44k1 = 5600, .n_48k = 6144, },
+ { .tmds = 32000000, .n_32k = 4096, .n_44k1 = 5733, .n_48k = 6144, },
+ { .tmds = 33750000, .n_32k = 4096, .n_44k1 = 6272, .n_48k = 6144, },
+ { .tmds = 36000000, .n_32k = 4096, .n_44k1 = 5684, .n_48k = 6144, },
+ { .tmds = 40000000, .n_32k = 4096, .n_44k1 = 5733, .n_48k = 6144, },
+ { .tmds = 49500000, .n_32k = 4096, .n_44k1 = 5488, .n_48k = 6144, },
+ { .tmds = 50000000, .n_32k = 4096, .n_44k1 = 5292, .n_48k = 6144, },
+ { .tmds = 54000000, .n_32k = 4096, .n_44k1 = 5684, .n_48k = 6144, },
+ { .tmds = 65000000, .n_32k = 4096, .n_44k1 = 7056, .n_48k = 6144, },
+ { .tmds = 68250000, .n_32k = 4096, .n_44k1 = 5376, .n_48k = 6144, },
+ { .tmds = 71000000, .n_32k = 4096, .n_44k1 = 7056, .n_48k = 6144, },
+ { .tmds = 72000000, .n_32k = 4096, .n_44k1 = 5635, .n_48k = 6144, },
+ { .tmds = 73250000, .n_32k = 4096, .n_44k1 = 14112, .n_48k = 6144, },
+ { .tmds = 74250000, .n_32k = 4096, .n_44k1 = 6272, .n_48k = 6144, },
+ { .tmds = 75000000, .n_32k = 4096, .n_44k1 = 5880, .n_48k = 6144, },
+ { .tmds = 78750000, .n_32k = 4096, .n_44k1 = 5600, .n_48k = 6144, },
+ { .tmds = 78800000, .n_32k = 4096, .n_44k1 = 5292, .n_48k = 6144, },
+ { .tmds = 79500000, .n_32k = 4096, .n_44k1 = 4704, .n_48k = 6144, },
+ { .tmds = 83500000, .n_32k = 4096, .n_44k1 = 7056, .n_48k = 6144, },
+ { .tmds = 85500000, .n_32k = 4096, .n_44k1 = 5488, .n_48k = 6144, },
+ { .tmds = 88750000, .n_32k = 4096, .n_44k1 = 14112, .n_48k = 6144, },
+ { .tmds = 97750000, .n_32k = 4096, .n_44k1 = 14112, .n_48k = 6144, },
+ { .tmds = 101000000, .n_32k = 4096, .n_44k1 = 7056, .n_48k = 6144, },
+ { .tmds = 106500000, .n_32k = 4096, .n_44k1 = 4704, .n_48k = 6144, },
+ { .tmds = 108000000, .n_32k = 4096, .n_44k1 = 5684, .n_48k = 6144, },
+ { .tmds = 115500000, .n_32k = 4096, .n_44k1 = 5712, .n_48k = 6144, },
+ { .tmds = 119000000, .n_32k = 4096, .n_44k1 = 5544, .n_48k = 6144, },
+ { .tmds = 135000000, .n_32k = 4096, .n_44k1 = 5488, .n_48k = 6144, },
+ { .tmds = 146250000, .n_32k = 4096, .n_44k1 = 6272, .n_48k = 6144, },
+ { .tmds = 148500000, .n_32k = 4096, .n_44k1 = 5488, .n_48k = 6144, },
+ { .tmds = 154000000, .n_32k = 4096, .n_44k1 = 5544, .n_48k = 6144, },
+ { .tmds = 162000000, .n_32k = 4096, .n_44k1 = 5684, .n_48k = 6144, },
+
+ /* For 297 MHz+ HDMI spec have some other rule for setting N */
+ { .tmds = 297000000, .n_32k = 3073, .n_44k1 = 4704, .n_48k = 5120, },
+ { .tmds = 594000000, .n_32k = 3073, .n_44k1 = 9408, .n_48k = 10240, },
+
+ /* End of table */
+ { .tmds = 0, .n_32k = 0, .n_44k1 = 0, .n_48k = 0, },
+};
+
+
static const u16 csc_coeff_default[3][4] = {
{ 0x2000, 0x0000, 0x0000, 0x0000 },
{ 0x0000, 0x2000, 0x0000, 0x0000 },
@@ -217,60 +273,117 @@ static void hdmi_set_cts_n(struct dw_hdmi *hdmi, unsigned int cts,
hdmi_writeb(hdmi, n & 0xff, HDMI_AUD_N1);
}
-static unsigned int hdmi_compute_n(unsigned int freq, unsigned long pixel_clk)
+static int hdmi_match_tmds_n_table(struct dw_hdmi *hdmi,
+ unsigned long pixel_clk,
+ unsigned long freq)
{
- unsigned int n = (128 * freq) / 1000;
- unsigned int mult = 1;
+ const struct dw_hdmi_plat_data *plat_data = hdmi->plat_data;
+ const struct dw_hdmi_audio_tmds_n *tmds_n = NULL;
+ int i;
- while (freq > 48000) {
- mult *= 2;
- freq /= 2;
+ if (plat_data->tmds_n_table) {
+ for (i = 0; plat_data->tmds_n_table[i].tmds != 0; i++) {
+ if (pixel_clk == plat_data->tmds_n_table[i].tmds) {
+ tmds_n = &plat_data->tmds_n_table[i];
+ break;
+ }
+ }
}
+ if (tmds_n == NULL) {
+ for (i = 0; common_tmds_n_table[i].tmds != 0; i++) {
+ if (pixel_clk == common_tmds_n_table[i].tmds) {
+ tmds_n = &common_tmds_n_table[i];
+ break;
+ }
+ }
+ }
+
+ if (tmds_n == NULL)
+ return -ENOENT;
+
switch (freq) {
case 32000:
- if (pixel_clk == 25175000)
- n = 4576;
- else if (pixel_clk == 27027000)
- n = 4096;
- else if (pixel_clk == 74176000 || pixel_clk == 148352000)
- n = 11648;
- else
- n = 4096;
- n *= mult;
- break;
-
+ return tmds_n->n_32k;
case 44100:
- if (pixel_clk == 25175000)
- n = 7007;
- else if (pixel_clk == 74176000)
- n = 17836;
- else if (pixel_clk == 148352000)
- n = 8918;
- else
- n = 6272;
- n *= mult;
- break;
-
+ case 88200:
+ case 176400:
+ return (freq / 44100) * tmds_n->n_44k1;
case 48000:
- if (pixel_clk == 25175000)
- n = 6864;
- else if (pixel_clk == 27027000)
- n = 6144;
- else if (pixel_clk == 74176000)
- n = 11648;
- else if (pixel_clk == 148352000)
- n = 5824;
- else
- n = 6144;
- n *= mult;
- break;
-
+ case 96000:
+ case 192000:
+ return (freq / 48000) * tmds_n->n_48k;
default:
- break;
+ return -ENOENT;
+ }
+}
+
+static u64 hdmi_audio_math_diff(unsigned int freq, unsigned int n,
+ unsigned int pixel_clk)
+{
+ u64 final, diff;
+ u64 cts;
+
+ final = (u64)pixel_clk * n;
+
+ cts = final;
+ do_div(cts, 128 * freq);
+
+ diff = final - (u64)cts * (128 * freq);
+
+ return diff;
+}
+
+static unsigned int hdmi_compute_n(struct dw_hdmi *hdmi,
+ unsigned long pixel_clk,
+ unsigned long freq)
+{
+ unsigned int min_n = DIV_ROUND_UP((128 * freq), 1500);
+ unsigned int max_n = (128 * freq) / 300;
+ unsigned int ideal_n = (128 * freq) / 1000;
+ unsigned int best_n_distance = ideal_n;
+ unsigned int best_n = 0;
+ u64 best_diff = U64_MAX;
+ int n;
+
+ /* If the ideal N could satisfy the audio math, then just take it */
+ if (hdmi_audio_math_diff(freq, ideal_n, pixel_clk) == 0)
+ return ideal_n;
+
+ for (n = min_n; n <= max_n; n++) {
+ u64 diff = hdmi_audio_math_diff(freq, n, pixel_clk);
+
+ if (diff < best_diff || (diff == best_diff &&
+ abs(n - ideal_n) < best_n_distance)) {
+ best_n = n;
+ best_diff = diff;
+ best_n_distance = abs(best_n - ideal_n);
+ }
+
+ /*
+ * The best N already satisfy the audio math, and also be
+ * the closest value to ideal N, so just cut the loop.
+ */
+ if ((best_diff == 0) && (abs(n - ideal_n) > best_n_distance))
+ break;
}
- return n;
+ return best_n;
+}
+
+static unsigned int hdmi_find_n(struct dw_hdmi *hdmi, unsigned long pixel_clk,
+ unsigned long sample_rate)
+{
+ int n;
+
+ n = hdmi_match_tmds_n_table(hdmi, pixel_clk, sample_rate);
+ if (n > 0)
+ return n;
+
+ dev_warn(hdmi->dev, "Rate %lu missing; compute N dynamically\n",
+ pixel_clk);
+
+ return hdmi_compute_n(hdmi, pixel_clk, sample_rate);
}
static void hdmi_set_clk_regenerator(struct dw_hdmi *hdmi,
@@ -280,7 +393,7 @@ static void hdmi_set_clk_regenerator(struct dw_hdmi *hdmi,
unsigned int n, cts;
u64 tmp;
- n = hdmi_compute_n(sample_rate, pixel_clk);
+ n = hdmi_find_n(hdmi, pixel_clk, sample_rate);
/*
* Compute the CTS value from the N value. Note that CTS and N
diff --git a/include/drm/bridge/dw_hdmi.h b/include/drm/bridge/dw_hdmi.h
index 26c06d5be23d..2fb760eb9797 100644
--- a/include/drm/bridge/dw_hdmi.h
+++ b/include/drm/bridge/dw_hdmi.h
@@ -28,6 +28,13 @@ enum dw_hdmi_devtype {
RK3399_HDMI,
};
+struct dw_hdmi_audio_tmds_n {
+ unsigned long tmds;
+ unsigned int n_32k;
+ unsigned int n_44k1;
+ unsigned int n_48k;
+};
+
struct dw_hdmi_mpll_config {
unsigned long mpixelclock;
struct {
@@ -50,6 +57,7 @@ struct dw_hdmi_phy_config {
struct dw_hdmi_plat_data {
enum dw_hdmi_devtype dev_type;
+ const struct dw_hdmi_audio_tmds_n *tmds_n_table;
const struct dw_hdmi_mpll_config *mpll_cfg;
const struct dw_hdmi_curr_ctrl *cur_ctr;
const struct dw_hdmi_phy_config *phy_config;
--
2.34.1