drm/nouveau/disp/dp: add support for eDP link rates

eDP 1.4 adds a table of link rates supported by the sink to DPCD, as
well as a LINK_RATE_SET register to select between the entries in it.

If present, we will use this data to generate our internal link rate
table rather than using the standard list based on MAX_LINK_RATE.

Some recent laptops report MAX_LINK_RATE=0, and require this support.

Signed-off-by: Ben Skeggs <bskeggs@redhat.com>
Reviewed-by: Lyude Paul <lyude@redhat.com>
Signed-off-by: Karol Herbst <kherbst@redhat.com>
Link: https://gitlab.freedesktop.org/drm/nouveau/-/merge_requests/17

1 files changed, 59 insertions, 4 deletions

diff --git a/drivers/gpu/drm/nouveau/nvkm/engine/disp/dp.c b/drivers/gpu/drm/nouveau/nvkm/engine/disp/dp.c
index ab78842371e8..8e09315b8fb3 100644
--- a/drivers/gpu/drm/nouveau/nvkm/engine/disp/dp.c
+++ b/drivers/gpu/drm/nouveau/nvkm/engine/disp/dp.c
@@ -278,7 +278,7 @@ nvkm_dp_train_cr(struct lt_state *lt)
 }
 
 static int
-nvkm_dp_train_links(struct nvkm_dp *dp)
+nvkm_dp_train_links(struct nvkm_dp *dp, int rate)
 {
 	struct nvkm_ior *ior = dp->outp.ior;
 	struct nvkm_disp *disp = dp->outp.disp;
@@ -359,7 +359,7 @@ nvkm_dp_train_links(struct nvkm_dp *dp)
 	}
 
 	/* Set desired link configuration on the sink. */
-	sink[0] = ior->dp.bw;
+	sink[0] = (dp->rate[rate].dpcd < 0) ? ior->dp.bw : 0;
 	sink[1] = ior->dp.nr;
 	if (ior->dp.ef)
 		sink[1] |= DPCD_LC01_ENHANCED_FRAME_EN;
@@ -368,6 +368,19 @@ nvkm_dp_train_links(struct nvkm_dp *dp)
 	if (ret)
 		return ret;
 
+	if (dp->rate[rate].dpcd >= 0) {
+		ret = nvkm_rdaux(dp->aux, DPCD_LC15_LINK_RATE_SET, &sink[0], sizeof(sink[0]));
+		if (ret)
+			return ret;
+
+		sink[0] &= ~DPCD_LC15_LINK_RATE_SET_MASK;
+		sink[0] |= dp->rate[rate].dpcd;
+
+		ret = nvkm_wraux(dp->aux, DPCD_LC15_LINK_RATE_SET, &sink[0], sizeof(sink[0]));
+		if (ret)
+			return ret;
+	}
+
 	/* Attempt to train the link in this configuration. */
 	for (lt.repeater = lt.repeaters; lt.repeater >= 0; lt.repeater--) {
 		if (lt.repeater)
@@ -453,7 +466,7 @@ nvkm_dp_train(struct nvkm_dp *dp, u32 dataKBps)
 				/* Program selected link configuration. */
 				ior->dp.bw = dp->rate[rate].rate / 27000;
 				ior->dp.nr = nr;
-				ret = nvkm_dp_train_links(dp);
+				ret = nvkm_dp_train_links(dp, rate);
 			}
 		}
 	}
@@ -553,6 +566,47 @@ done:
 }
 
 static bool
+nvkm_dp_enable_supported_link_rates(struct nvkm_dp *dp)
+{
+	u8 sink_rates[DPCD_RC10_SUPPORTED_LINK_RATES__SIZE];
+	int i, j, k;
+
+	if (dp->outp.conn->info.type != DCB_CONNECTOR_eDP ||
+	    dp->dpcd[DPCD_RC00_DPCD_REV] < 0x13 ||
+	    nvkm_rdaux(dp->aux, DPCD_RC10_SUPPORTED_LINK_RATES(0), sink_rates, sizeof(sink_rates)))
+		return false;
+
+	for (i = 0; i < ARRAY_SIZE(sink_rates); i += 2) {
+		const u32 rate = ((sink_rates[i + 1] << 8) | sink_rates[i]) * 200 / 10;
+
+		if (!rate || WARN_ON(dp->rates == ARRAY_SIZE(dp->rate)))
+			break;
+
+		if (rate > dp->outp.info.dpconf.link_bw * 27000) {
+			OUTP_DBG(&dp->outp, "rate %d !outp", rate);
+			continue;
+		}
+
+		for (j = 0; j < dp->rates; j++) {
+			if (rate > dp->rate[j].rate) {
+				for (k = dp->rates; k > j; k--)
+					dp->rate[k] = dp->rate[k - 1];
+				break;
+			}
+		}
+
+		dp->rate[j].dpcd = i / 2;
+		dp->rate[j].rate = rate;
+		dp->rates++;
+	}
+
+	for (i = 0; i < dp->rates; i++)
+		OUTP_DBG(&dp->outp, "link_rate[%d] = %d", dp->rate[i].dpcd, dp->rate[i].rate);
+
+	return dp->rates != 0;
+}
+
+static bool
 nvkm_dp_enable(struct nvkm_dp *dp, bool enable)
 {
 	struct nvkm_i2c_aux *aux = dp->aux;
@@ -603,12 +657,13 @@ nvkm_dp_enable(struct nvkm_dp *dp, bool enable)
 			if (dp->lttprs && dp->lttpr[1])
 				rate_max = min_t(int, rate_max, dp->lttpr[1]);
 
-			if (1) {
+			if (!nvkm_dp_enable_supported_link_rates(dp)) {
 				for (rate = rates; *rate; rate++) {
 					if (*rate <= rate_max) {
 						if (WARN_ON(dp->rates == ARRAY_SIZE(dp->rate)))
 							break;
 
+						dp->rate[dp->rates].dpcd = -1;
 						dp->rate[dp->rates].rate = *rate * 27000;
 						dp->rates++;
 					}