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Subject[PATCH 2/2] fixup! drm/bridge: ti-sn65dsi86: Skip non-standard DP rates
Date
From: Rob Clark <robdclark@chromium.org>

---
Note however, the panel I have on the yoga c630 is not eDP 1.4+, so I
cannot test that path. But I think it looks correct.

drivers/gpu/drm/bridge/ti-sn65dsi86.c | 110 +++++++++++++++++++++-----
1 file changed, 89 insertions(+), 21 deletions(-)

diff --git a/drivers/gpu/drm/bridge/ti-sn65dsi86.c b/drivers/gpu/drm/bridge/ti-sn65dsi86.c
index 976f98991b3d..1cb53be7c9e9 100644
--- a/drivers/gpu/drm/bridge/ti-sn65dsi86.c
+++ b/drivers/gpu/drm/bridge/ti-sn65dsi86.c
@@ -102,6 +102,9 @@ struct ti_sn_bridge {
struct gpio_desc *enable_gpio;
struct regulator_bulk_data supplies[SN_REGULATOR_SUPPLY_NUM];
int dp_lanes;
+ u8 edp_dpcd[EDP_DISPLAY_CTL_CAP_SIZE];
+ int num_sink_rates;
+ int sink_rate_idxs[DP_MAX_SUPPORTED_RATES];
};

static const struct regmap_range ti_sn_bridge_volatile_ranges[] = {
@@ -454,15 +457,6 @@ static const unsigned int ti_sn_bridge_dp_rate_lut[] = {
0, 1620, 2160, 2430, 2700, 3240, 4320, 5400
};

-/**
- * A table indicating which of the rates in ti_sn_bridge_dp_rate_lut
- * is as per the DP spec (AKA a standard) as opposed to an intermediate
- * rate.
- */
-static const bool ti_sn_bridge_dp_rate_standard[] = {
- false, true, false, false, true, false, false, true
-};
-
static int ti_sn_bridge_calc_min_dp_rate_idx(struct ti_sn_bridge *pdata)
{
unsigned int bit_rate_khz, dp_rate_mhz;
@@ -573,11 +567,95 @@ static unsigned int ti_sn_get_max_lanes(struct ti_sn_bridge *pdata)
return data & DP_LANE_COUNT_MASK;
}

+/* TODO possibly fold ti_sn_get_max_lanes() into this? */
+static void ti_sn_read_sink_config(struct ti_sn_bridge *pdata)
+{
+ memset(pdata->edp_dpcd, 0, sizeof(pdata->edp_dpcd));
+
+ /*
+ * Read the eDP display control registers.
+ *
+ * Do this independent of DP_DPCD_DISPLAY_CONTROL_CAPABLE bit in
+ * DP_EDP_CONFIGURATION_CAP, because some buggy displays do not have it
+ * set, but require eDP 1.4+ detection (e.g. for supported link rates
+ * method). The display control registers should read zero if they're
+ * not supported anyway.
+ */
+ if (drm_dp_dpcd_read(&pdata->aux, DP_EDP_DPCD_REV,
+ pdata->edp_dpcd, sizeof(pdata->edp_dpcd)) ==
+ sizeof(pdata->edp_dpcd))
+ DRM_DEBUG_KMS("eDP DPCD: %*ph\n", (int) sizeof(pdata->edp_dpcd),
+ pdata->edp_dpcd);
+
+ /* Read the eDP 1.4+ supported link rates. */
+ if (pdata->edp_dpcd[0] >= DP_EDP_14) {
+ __le16 sink_rates[DP_MAX_SUPPORTED_RATES];
+ int i, j;
+
+ drm_dp_dpcd_read(&pdata->aux, DP_SUPPORTED_LINK_RATES,
+ sink_rates, sizeof(sink_rates));
+
+ for (i = 0; i < ARRAY_SIZE(sink_rates); i++) {
+ int val = le16_to_cpu(sink_rates[i]);
+ int rate_mhz;
+
+ if (val == 0)
+ break;
+
+ /* Value read multiplied by 200kHz gives the per-lane
+ * link rate in kHz. The source rates are, however,
+ * stored in MHz
+ */
+ rate_mhz = DIV_ROUND_UP(val * 200, 1000);
+
+ /* If the rate is also supported by the bridge, add it
+ * to the table of supported rates:
+ */
+ for (j = 1; j < ARRAY_SIZE(ti_sn_bridge_dp_rate_lut); j++) {
+ if (rate_mhz == ti_sn_bridge_dp_rate_lut[j]) {
+ pdata->sink_rate_idxs[pdata->num_sink_rates++] = j;
+ break;
+ }
+ }
+ }
+ pdata->num_sink_rates = i;
+ } else {
+ int i;
+
+ /**
+ * A table indicating which of the rates in ti_sn_bridge_dp_rate_lut
+ * is as per the DP spec (AKA a standard) as opposed to an intermediate
+ * rate.
+ */
+ static const bool ti_sn_bridge_dp_rate_standard[] = {
+ false, true, false, false, true, false, false, true
+ };
+
+ /* if prior to eDP 1.4, then just use the supported standard rates: */
+ for (i = 1; i < ARRAY_SIZE(ti_sn_bridge_dp_rate_lut); i++) {
+ if (!ti_sn_bridge_dp_rate_standard[i])
+ continue;
+ pdata->sink_rate_idxs[pdata->num_sink_rates++] = i;
+ }
+ }
+}
+
static int ti_sn_link_training(struct ti_sn_bridge *pdata, int dp_rate_idx,
const char **last_err_str)
{
unsigned int val;
int ret;
+ int i;
+
+ /* check for supported rate: */
+ for (i = 0; i < pdata->num_sink_rates; i++)
+ if (pdata->sink_rate_idxs[i] == dp_rate_idx)
+ break;
+
+ if (i == pdata->num_sink_rates) {
+ *last_err_str = "Unsupported rate";
+ return -EINVAL;
+ }

/* set dp clk frequency value */
regmap_update_bits(pdata->regmap, SN_DATARATE_CONFIG_REG,
@@ -624,6 +702,8 @@ static void ti_sn_bridge_enable(struct drm_bridge *bridge)
unsigned int val;
int ret = -EINVAL;

+ ti_sn_read_sink_config(pdata);
+
/*
* Run with the maximum number of lanes that the DP sink supports.
*
@@ -669,18 +749,6 @@ static void ti_sn_bridge_enable(struct drm_bridge *bridge)
for (dp_rate_idx = ti_sn_bridge_calc_min_dp_rate_idx(pdata);
dp_rate_idx <= max_dp_rate_idx;
dp_rate_idx++) {
- /*
- * To be on the safe side, we'll skip all non-standard
- * rates and move up to the next standard one. This is
- * because some panels will pass link training with a non-
- * standard rate but just show garbage. If the non-standard
- * rates are useful we should figure out how to enable them
- * through querying the panel, having a per-panel whitelist,
- * or adding a DT property.
- */
- if (!ti_sn_bridge_dp_rate_standard[dp_rate_idx])
- continue;
-
ret = ti_sn_link_training(pdata, dp_rate_idx, &last_err_str);
if (!ret)
break;
--
2.23.0
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