drm/nouveau/disp/dp: support training to highest rate, rather than a target

We really want this for, at least, MST devices.

Signed-off-by: Ben Skeggs <bskeggs@redhat.com>

1 files changed, 34 insertions, 23 deletions

diff --git a/drivers/gpu/drm/nouveau/core/engine/disp/dport.c b/drivers/gpu/drm/nouveau/core/engine/disp/dport.c
index 758d2eace928..3814c3d33812 100644
--- a/drivers/gpu/drm/nouveau/core/engine/disp/dport.c
+++ b/drivers/gpu/drm/nouveau/core/engine/disp/dport.c
@@ -293,20 +293,36 @@ dp_link_train_fini(struct dp_state *dp)
         nvbios_exec(&init);
 }
 
+static const struct dp_rates {
+        u32 rate;
+        u8  bw;
+        u8  nr;
+} nouveau_dp_rates[] = {
+        { 2160000, 0x14, 4 },
+        { 1080000, 0x0a, 4 },
+        { 1080000, 0x14, 2 },
+        {  648000, 0x06, 4 },
+        {  540000, 0x0a, 2 },
+        {  540000, 0x14, 1 },
+        {  324000, 0x06, 2 },
+        {  270000, 0x0a, 1 },
+        {  162000, 0x06, 1 },
+        {}
+};
+
 int
 nouveau_dp_train(struct nouveau_disp *disp, const struct nouveau_dp_func *func,
                  struct dcb_output *outp, int head, u32 datarate)
 {
         struct nouveau_bios *bios = nouveau_bios(disp);
         struct nouveau_i2c *i2c = nouveau_i2c(disp);
+        const struct dp_rates *cfg = nouveau_dp_rates;
         struct dp_state _dp = {
                 .disp = disp,
                 .func = func,
                 .outp = outp,
                 .head = head,
         }, *dp = &_dp;
-        const u32 bw_list[] = { 540000, 270000, 162000, 0 };
-        const u32 *link_bw = bw_list;
         u8  hdr, cnt, len;
         u32 data;
         int ret;
@@ -338,8 +354,8 @@ nouveau_dp_train(struct nouveau_disp *disp, const struct nouveau_dp_func *func,
                  * so results at best in an UPDATE hanging, and at worst
                  * with PDISP running away to join the circus.
                  */
-                dp->dpcd[1] = link_bw[0] / 27000;
-                dp->dpcd[2] = 4;
+                dp->dpcd[1] = dp->outp->dpconf.link_bw;
+                dp->dpcd[2] = dp->outp->dpconf.link_nr;
                 dp->dpcd[3] = 0x00;
                 ERR("failed to read DPCD\n");
         }
@@ -355,26 +371,24 @@ nouveau_dp_train(struct nouveau_disp *disp, const struct nouveau_dp_func *func,
                 dp->dpcd[1] = dp->outp->dpconf.link_bw;
         dp->pc2 = dp->dpcd[2] & DPCD_RC02_TPS3_SUPPORTED;
 
-        /* adjust required bandwidth for 8B/10B coding overhead */
-        datarate = (datarate / 8) * 10;
+        /* restrict link config to the lowest required rate, if requested */
+        if (datarate) {
+                datarate = (datarate / 8) * 10; /* 8B/10B coding overhead */
+                while (cfg[1].rate >= datarate)
+                        cfg++;
+        }
+        cfg--;
 
         /* enable down-spreading and execute pre-train script from vbios */
         dp_link_train_init(dp, dp->dpcd[3] & 0x01);
 
-        /* start off at highest link rate supported by encoder and display */
-        while (*link_bw > (dp->dpcd[1] * 27000))
-                link_bw++;
-
-        while ((ret = -EIO) && link_bw[0]) {
-                /* find minimum required lane count at this link rate */
-                dp->link_nr = dp->dpcd[2] & DPCD_RC02_MAX_LANE_COUNT;
-                while ((dp->link_nr >> 1) * link_bw[0] > datarate)
-                        dp->link_nr >>= 1;
-
-                /* drop link rate to minimum with this lane count */
-                while ((link_bw[1] * dp->link_nr) > datarate)
-                        link_bw++;
-                dp->link_bw = link_bw[0];
+        while (ret = -EIO, (++cfg)->rate) {
+                /* select next configuration supported by encoder and sink */
+                while (cfg->nr > (dp->dpcd[2] & DPCD_RC02_MAX_LANE_COUNT) ||
+                       cfg->bw > (dp->dpcd[DPCD_RC01_MAX_LINK_RATE]))
+                        cfg++;
+                dp->link_bw = cfg->bw * 27000;
+                dp->link_nr = cfg->nr;
 
                 /* program selected link configuration */
                 ret = dp_set_link_config(dp);
@@ -391,9 +405,6 @@ nouveau_dp_train(struct nouveau_disp *disp, const struct nouveau_dp_func *func,
                          */
                         break;
                 }
-
-                /* retry at lower rate */
-                link_bw++;
         }
 
         /* finish link training */