[Intel-gfx] [v3 1/7] i915/dp/fec: Cache the FEC_CAPABLE DPCD register

[Anusha Srivatsa]

Similar to DSC DPCD registers, let us cache
FEC_CAPABLE register to avoid using stale
values. With this we can avoid aux reads
everytime and instead read the cached values.

v2: Avoid using memset and array for a single
field. (Manasi,Jani)

Suggested-by: Jani Nikula <jani.nikula at linux.intel.com>
Cc: Jani Nikula <jani.nikula at linux.intel.com>
Cc: Ville Syrjala <ville.syrjala 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/i915/intel_dp.c  | 10 ++++++++++
 drivers/gpu/drm/i915/intel_drv.h |  1 +
 2 files changed, 11 insertions(+)

diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
index 5a638503e36a..16d1db7c9398 100644
--- a/drivers/gpu/drm/i915/intel_dp.c
+++ b/drivers/gpu/drm/i915/intel_dp.c
@@ -4198,9 +4198,13 @@ static void intel_dp_get_dsc_sink_cap(struct intel_dp *intel_dp)
 	/*
 	 *Clear the cached register set to avoid using stale values
 	 * for the sinks that do not support DSC.
+	 * Similarly, clear the cached FEC register.
 	 */
 	memset(intel_dp->dsc_dpcd, 0, sizeof(intel_dp->dsc_dpcd));
 
+	/* Clear fec_capable to avoid using stale values */
+	intel_dp->fec_capable = 0;
+
 	/* Cache the DSC DPCD if eDP or DP rev >= 1.4 */
 	if (intel_dp->dpcd[DP_DPCD_REV] >= 0x14 ||
 	    intel_dp->edp_dpcd[0] >= DP_EDP_14) {
@@ -4214,6 +4218,12 @@ static void intel_dp_get_dsc_sink_cap(struct intel_dp *intel_dp)
 			      (int)sizeof(intel_dp->dsc_dpcd),
 			      intel_dp->dsc_dpcd);
 	}
+	/* FEC is supported only on DP 1.4 */
+	if (!intel_dp_is_edp(intel_dp) && intel_dp->dpcd[DP_DPCD_REV] >= 0x14) {
+		if (drm_dp_dpcd_readb(&intel_dp->aux, DP_FEC_CAPABILITY,
+				      &intel_dp->fec_capable) < 0)
+			DRM_ERROR("Failed to read FEC DPCD register\n");
+	}
 }
 
 static bool
diff --git a/drivers/gpu/drm/i915/intel_drv.h b/drivers/gpu/drm/i915/intel_drv.h
index 16bbc3768e02..9a94c6544bf5 100644
--- a/drivers/gpu/drm/i915/intel_drv.h
+++ b/drivers/gpu/drm/i915/intel_drv.h
@@ -1119,6 +1119,7 @@ struct intel_dp {
 	uint8_t downstream_ports[DP_MAX_DOWNSTREAM_PORTS];
 	uint8_t edp_dpcd[EDP_DISPLAY_CTL_CAP_SIZE];
 	u8 dsc_dpcd[DP_DSC_RECEIVER_CAP_SIZE];
+	u8 fec_capable;
 	/* source rates */
 	int num_source_rates;
 	const int *source_rates;
-- 
2.17.1