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;