[PATCH v3 9/9] drm/bridge: ti-sn65dsi86: Avoid invalid rates

Douglas Anderson
2019-12-18T22:36:16Z

Based on work by Bjorn Andersson <bjorn.andersson@linaro.org>,
Jeffrey Hugo <jeffrey.l.hugo@gmail.com>, and
Rob Clark <robdclark@chromium.org>.

Let's read the SUPPORTED_LINK_RATES and/or MAX_LINK_RATE (depending on
the eDP version of the sink) to figure out what eDP rates are
supported and pick the ideal one.

NOTE: I have only personally tested this code on eDP panels that are
1.3 or older. Code reading SUPPORTED_LINK_RATES for DP 1.4+ was
tested by hacking the code to pretend that a table was there.

Signed-off-by: Douglas Anderson <dianders@chromium.org>
---

Changes in v3:
- Init rate_valid table, don't rely on stack being 0 (oops).
- Rename rate_times_200khz to rate_per_200khz.
- Loop over the ti_sn_bridge_dp_rate_lut table, making code smaller.
- Use 'true' instead of 1 for bools.
- Added note to commit message noting DP 1.4+ isn't well tested.

Changes in v2:
- Patch ("Avoid invalid rates") replaces ("Skip non-standard DP rates")

drivers/gpu/drm/bridge/ti-sn65dsi86.c | 100 +++++++++++++++++++-------
1 file changed, 75 insertions(+), 25 deletions(-)

diff --git a/drivers/gpu/drm/bridge/ti-sn65dsi86.c b/drivers/gpu/drm/bridge/ti-sn65dsi86.c
index e1b817ccd9c7..a57c6108cb1f 100644
--- a/drivers/gpu/drm/bridge/ti-sn65dsi86.c
+++ b/drivers/gpu/drm/bridge/ti-sn65dsi86.c
@@ -475,39 +475,85 @@ static int ti_sn_bridge_calc_min_dp_rate_idx(struct ti_sn_bridge *pdata)
return i;
}

-static int ti_sn_bridge_get_max_dp_rate_idx(struct ti_sn_bridge *pdata)
+static void ti_sn_bridge_read_valid_rates(struct ti_sn_bridge *pdata,
+ bool rate_valid[])
{
- u8 data;
+ unsigned int rate_per_200khz;
+ unsigned int rate_mhz;
+ u8 dpcd_val;
int ret;
+ int i, j;
+
+ ret = drm_dp_dpcd_readb(&pdata->aux, DP_EDP_DPCD_REV, &dpcd_val);
+ if (ret != 1) {
+ DRM_DEV_ERROR(pdata->dev,
+ "Can't read eDP rev (%d), assuming 1.1\n", ret);
+ dpcd_val = DP_EDP_11;
+ }
+
+ if (dpcd_val >= DP_EDP_14) {
+ /* eDP 1.4 devices must provide a custom table */
+ __le16 sink_rates[DP_MAX_SUPPORTED_RATES];
+
+ ret = drm_dp_dpcd_read(&pdata->aux, DP_SUPPORTED_LINK_RATES,
+ sink_rates, sizeof(sink_rates));
+
+ if (ret != sizeof(sink_rates)) {
+ DRM_DEV_ERROR(pdata->dev,
+ "Can't read supported rate table (%d)\n", ret);
+
+ /* By zeroing we'll fall back to DP_MAX_LINK_RATE. */
+ memset(sink_rates, 0, sizeof(sink_rates));
+ }
+
+ for (i = 0; i < ARRAY_SIZE(sink_rates); i++) {
+ rate_per_200khz = le16_to_cpu(sink_rates[i]);
+
+ if (!rate_per_200khz)
+ break;
+
+ rate_mhz = rate_per_200khz * 200 / 1000;
+ for (j = 0;
+ j < ARRAY_SIZE(ti_sn_bridge_dp_rate_lut);
+ j++) {
+ if (ti_sn_bridge_dp_rate_lut[j] == rate_mhz)
+ rate_valid[j] = true;
+ }
+ }
+
+ for (i = 0; i < ARRAY_SIZE(ti_sn_bridge_dp_rate_lut); i++) {
+ if (rate_valid[i])
+ return;
+ }
+ DRM_DEV_ERROR(pdata->dev,
+ "No matching eDP rates in table; falling back\n");
+ }

- ret = drm_dp_dpcd_readb(&pdata->aux, DP_MAX_LINK_RATE, &data);
+ /* On older versions best we can do is use DP_MAX_LINK_RATE */
+ ret = drm_dp_dpcd_readb(&pdata->aux, DP_MAX_LINK_RATE, &dpcd_val);
if (ret != 1) {
DRM_DEV_ERROR(pdata->dev,
"Can't read max rate (%d); assuming 5.4 GHz\n",
ret);
- return ARRAY_SIZE(ti_sn_bridge_dp_rate_lut) - 1;
+ dpcd_val = DP_LINK_BW_5_4;
}

- /*
- * Return an index into ti_sn_bridge_dp_rate_lut. Just hardcode
- * these indicies since it's not like the register spec is ever going
- * to change and a loop would just be more complicated. Apparently
- * the DP sink can only return these few rates as supported even
- * though the bridge allows some rates in between.
- */
- switch (data) {
- case DP_LINK_BW_1_62:
- return 1;
- case DP_LINK_BW_2_7:
- return 4;
+ switch (dpcd_val) {
+ default:
+ DRM_DEV_ERROR(pdata->dev,
+ "Unexpected max rate (%#x); assuming 5.4 GHz\n",
+ (int)dpcd_val);
+ /* fall through */
case DP_LINK_BW_5_4:
- return 7;
+ rate_valid[7] = 1;
+ /* fall through */
+ case DP_LINK_BW_2_7:
+ rate_valid[4] = 1;
+ /* fall through */
+ case DP_LINK_BW_1_62:
+ rate_valid[1] = 1;
+ break;
}
-
- DRM_DEV_ERROR(pdata->dev,
- "Unexpected max data rate (%#x); assuming 5.4 GHz\n",
- (int)data);
- return ARRAY_SIZE(ti_sn_bridge_dp_rate_lut) - 1;
}

static void ti_sn_bridge_set_video_timings(struct ti_sn_bridge *pdata)
@@ -609,9 +655,9 @@ static int ti_sn_link_training(struct ti_sn_bridge *pdata, int dp_rate_idx,
static void ti_sn_bridge_enable(struct drm_bridge *bridge)
{
struct ti_sn_bridge *pdata = bridge_to_ti_sn_bridge(bridge);
+ bool rate_valid[ARRAY_SIZE(ti_sn_bridge_dp_rate_lut)] = { };
const char *last_err_str = "No supported DP rate";
int dp_rate_idx;
- int max_dp_rate_idx;
unsigned int val;
int ret = -EINVAL;

@@ -655,11 +701,15 @@ static void ti_sn_bridge_enable(struct drm_bridge *bridge)
regmap_update_bits(pdata->regmap, SN_SSC_CONFIG_REG, DP_NUM_LANES_MASK,
val);

+ ti_sn_bridge_read_valid_rates(pdata, rate_valid);
+
/* Train until we run out of rates */
- max_dp_rate_idx = ti_sn_bridge_get_max_dp_rate_idx(pdata);
for (dp_rate_idx = ti_sn_bridge_calc_min_dp_rate_idx(pdata);
- dp_rate_idx <= max_dp_rate_idx;
+ dp_rate_idx < ARRAY_SIZE(ti_sn_bridge_dp_rate_lut);
dp_rate_idx++) {
+ if (!rate_valid[dp_rate_idx])
+ continue;
+
ret = ti_sn_link_training(pdata, dp_rate_idx, &last_err_str);
if (!ret)
break;
--
2.24.1.735.g03f4e72817-goog