drm/nouveau/pm: detect when we need dll disabled for gddr3

Fixes minor flickering on NVS295 when at perflvl 0.
Signed-off-by: Ben Skeggs <bskeggs@redhat.com>
Signed-off-by: Martin Peres <martin.peres@labri.fr>

drivers/gpu/drm/nouveau/nouveau_mem.c

@@ -735,6 +735,8 @@ nouveau_mem_gddr3_mr(struct drm_device *dev, u32 freq,
 		     struct nouveau_pm_memtiming *boot,
 		     struct nouveau_pm_memtiming *t)
 {
+	u8 rver, rlen, *ramcfg = nouveau_perf_ramcfg(dev, freq, &rver, &rlen);
+
 	if (len < 15) {
 		t->drive_strength = boot->drive_strength;
 		t->odt = boot->odt;
@@ -763,9 +765,17 @@ nouveau_mem_gddr3_mr(struct drm_device *dev, u32 freq,
 		   /* CAS */
 		   ((nv_mem_cl_lut_gddr3[e->tCL] & 0x7) << 4) |
 		   ((nv_mem_cl_lut_gddr3[e->tCL] & 0x8) >> 2);
+
 	t->mr[1] = (boot->mr[1] & 0x100f40) | t->drive_strength |
 		   (t->odt << 2) |
 		   (nv_mem_wr_lut_gddr3[e->tWR] & 0xf) << 4;
+	if (ramcfg && rver == 0x00) {
+		/* DLL enable/disable */
+		t->mr[1] &= ~0x00000040;
+		if (ramcfg[3] & 0x08)
+			t->mr[1] |= 0x00000040;
+	}
+
 	t->mr[2] = boot->mr[2];
 
 	NV_DEBUG(dev, "(%u) MR: %08x %08x %08x", t->id,

drivers/gpu/drm/nouveau/nouveau_perf.c

@@ -139,7 +139,7 @@ nouveau_perf_rammap(struct drm_device *dev, u32 freq,
 	return NULL;
 }
 
-static u8 *
+u8 *
 nouveau_perf_ramcfg(struct drm_device *dev, u32 freq, u8 *ver, u8 *len)
 {
 	struct drm_nouveau_private *dev_priv = dev->dev_private;

drivers/gpu/drm/nouveau/nouveau_pm.h

@@ -60,6 +60,7 @@ int  nouveau_voltage_gpio_set(struct drm_device *, int voltage);
 void nouveau_perf_init(struct drm_device *);
 void nouveau_perf_fini(struct drm_device *);
 u8 *nouveau_perf_timing(struct drm_device *, u32 freq, u8 *ver, u8 *len);
+u8 *nouveau_perf_ramcfg(struct drm_device *, u32 freq, u8 *ver, u8 *len);
 
 /* nouveau_mem.c */
 void nouveau_mem_timing_init(struct drm_device *);