[RFC 09/13] drm/dp: Enable alternate scrambler when supported

[Thierry Reding]

From: Thierry Reding <treding at nvidia.com>

If the sink is eDP and supports the alternate scrambler reset, enable
it.

Signed-off-by: Thierry Reding <treding at nvidia.com>
---
 drivers/gpu/drm/drm_dp_helper.c | 9 +++++++++
 include/drm/drm_dp_helper.h     | 1 +
 2 files changed, 10 insertions(+)

diff --git a/drivers/gpu/drm/drm_dp_helper.c b/drivers/gpu/drm/drm_dp_helper.c
index d503cc3f1772..543349e14481 100644
--- a/drivers/gpu/drm/drm_dp_helper.c
+++ b/drivers/gpu/drm/drm_dp_helper.c
@@ -334,6 +334,8 @@ int drm_dp_link_probe(struct drm_dp_aux *aux, struct drm_dp_link *link)
 		link->capabilities |= DP_LINK_CAP_ANSI_8B10B;
 
 	if (values[13] & DP_ALTERNATE_SCRAMBLER_RESET_CAP) {
+		link->capabilities |= DP_LINK_CAP_ALTERNATE_SCRAMBLER_RESET;
+
 		err = drm_dp_dpcd_readb(aux, DP_EDP_DPCD_REV, &value);
 		if (err < 0)
 			return err;
@@ -468,6 +470,13 @@ int drm_dp_link_configure(struct drm_dp_aux *aux, struct drm_dp_link *link)
 	if (err < 0)
 		return err;
 
+	if (link->capabilities & DP_LINK_CAP_ALTERNATE_SCRAMBLER_RESET) {
+		err = drm_dp_dpcd_writeb(aux, DP_EDP_CONFIGURATION_SET,
+					 DP_ALTERNATE_SCRAMBLER_RESET_ENABLE);
+		if (err < 0)
+			return err;
+	}
+
 	return 0;
 }
 EXPORT_SYMBOL(drm_dp_link_configure);
diff --git a/include/drm/drm_dp_helper.h b/include/drm/drm_dp_helper.h
index 2165b9ef8504..600347f8cdd4 100644
--- a/include/drm/drm_dp_helper.h
+++ b/include/drm/drm_dp_helper.h
@@ -758,6 +758,7 @@ int drm_dp_dpcd_read_link_status(struct drm_dp_aux *aux,
 #define DP_LINK_CAP_FAST_TRAINING (1 << 1)
 #define DP_LINK_CAP_ANSI_8B10B (1 << 2)
 #define DP_LINK_CAP_TPS3 (1 << 3)
+#define DP_LINK_CAP_ALTERNATE_SCRAMBLER_RESET (1 << 4)
 
 struct drm_dp_link {
 	unsigned char revision;
-- 
2.4.5