[Intel-gfx] [PATCH 1/5] drm/dp/fec: DRM helper for Forward Error Correction

[Anusha Srivatsa]

From: "Srivatsa, Anusha" <anusha.srivatsa at intel.com>

DP 1.4 has Forward Error Correction Support(FEC).
Add helper function to check if the sink device
supports FEC.

v2: Separate the helper and the code that uses the helper into
two separate patches. (Manasi)

v3:
- Move the code to drm_dp_helper.c (Manasi)
- change the return type, code style changes (Gaurav)
- Use drm_dp_dpcd_readb instead of drm_dp_dpcd_read. (Jani)

Cc: Ville Syrjala <ville.syrjala at linux.intel.com>
Cc: Jani Nikula <jani.nikula at linux.intel.com>
Cc: Manasi Navare <manasi.d.navare at intel.com>
Signed-off-by: Anusha Srivatsa <anusha.srivatsa at intel.com>
---
 drivers/gpu/drm/drm_dp_helper.c | 14 ++++++++++++++
 include/drm/drm_dp_helper.h     |  3 +++
 2 files changed, 17 insertions(+)

diff --git a/drivers/gpu/drm/drm_dp_helper.c b/drivers/gpu/drm/drm_dp_helper.c
index 7dc61d1..2e127b9 100644
--- a/drivers/gpu/drm/drm_dp_helper.c
+++ b/drivers/gpu/drm/drm_dp_helper.c
@@ -1425,3 +1425,17 @@ u8 drm_dp_dsc_sink_max_color_depth(const u8 dsc_dpcd[DP_DSC_RECEIVER_CAP_SIZE])
 	return 0;
 }
 EXPORT_SYMBOL(drm_dp_dsc_sink_max_color_depth);
+
+/* Forward Error Correction support for DP 1.4 */
+int drm_dp_sink_supports_fec(struct drm_dp_aux *aux)
+{
+	int fec_err;
+	u8 fec_cap;
+
+	fec_err = drm_dp_dpcd_readb(aux, DP_FEC_CAPABILITY, &fec_cap);
+	if (fec_err < 0)
+		return fec_err;
+
+	return fec_cap & DP_FEC_CAPABLE;
+}
+EXPORT_SYMBOL(drm_dp_sink_supports_fec);
diff --git a/include/drm/drm_dp_helper.h b/include/drm/drm_dp_helper.h
index f178933..d958c7d 100644
--- a/include/drm/drm_dp_helper.h
+++ b/include/drm/drm_dp_helper.h
@@ -1270,6 +1270,9 @@ void drm_dp_aux_unregister(struct drm_dp_aux *aux);
 int drm_dp_start_crc(struct drm_dp_aux *aux, struct drm_crtc *crtc);
 int drm_dp_stop_crc(struct drm_dp_aux *aux);
 
+/* Forward Error Correction Support on DP 1.4 */
+int drm_dp_sink_supports_fec(struct drm_dp_aux *aux);
+
 struct drm_dp_dpcd_ident {
 	u8 oui[3];
 	u8 device_id[6];
-- 
2.7.4