diff mbox series

[L,2/2] drm/i915: Explain the magic numbers for AUX SYNC/precharge length

Message ID 20230506180409.580489-3-kai.heng.feng@canonical.com
State New
Headers show
Series Update I915 PSR calculation on Linux 6.2 | expand

Commit Message

Kai-Heng Feng May 6, 2023, 6:04 p.m. UTC 
From: Ville Syrjälä <ville.syrjala@linux.intel.com>

BugLink: https://bugs.launchpad.net/bugs/2018655

Replace the hardcoded final numbers in the AUX SYNC/precharge
setup, and derive those from numbers from the (e)DP specs.

The new functions can serve as the single point of truth for
the number of SYNC pulses we use.

Cc: Jouni Högander <jouni.hogander@intel.com>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230329172434.18744-2-ville.syrjala@linux.intel.com
Reviewed-by: Jouni Högander <jouni.hogander@intel.com>
(cherry picked from commit 26bfc3f36f2104c174dfc72415547d5c28ef3f1c)
Signed-off-by: Kai-Heng Feng <kai.heng.feng@canonical.com>
---
 drivers/gpu/drm/i915/display/intel_dp_aux.c | 32 +++++++++++++++++++--
 1 file changed, 29 insertions(+), 3 deletions(-)
diff mbox series

Patch

diff --git a/drivers/gpu/drm/i915/display/intel_dp_aux.c b/drivers/gpu/drm/i915/display/intel_dp_aux.c
index d5fed2eb66d2..f4b315b302da 100644
--- a/drivers/gpu/drm/i915/display/intel_dp_aux.c
+++ b/drivers/gpu/drm/i915/display/intel_dp_aux.c
@@ -120,6 +120,32 @@  static u32 skl_get_aux_clock_divider(struct intel_dp *intel_dp, int index)
 	return index ? 0 : 1;
 }
 
+static int intel_dp_aux_sync_len(void)
+{
+	int precharge = 16; /* 10-16 */
+	int preamble = 16;
+
+	return precharge + preamble;
+}
+
+static int intel_dp_aux_fw_sync_len(void)
+{
+	int precharge = 16; /* 10-16 */
+	int preamble = 8;
+
+	return precharge + preamble;
+}
+
+static int g4x_dp_aux_precharge_len(void)
+{
+	int precharge_min = 10;
+	int preamble = 16;
+
+	/* HW wants the length of the extra precharge in 2us units */
+	return (intel_dp_aux_sync_len() -
+		precharge_min - preamble) / 2;
+}
+
 static u32 g4x_get_aux_send_ctl(struct intel_dp *intel_dp,
 				int send_bytes,
 				u32 aux_clock_divider)
@@ -142,7 +168,7 @@  static u32 g4x_get_aux_send_ctl(struct intel_dp *intel_dp,
 	       timeout |
 	       DP_AUX_CH_CTL_RECEIVE_ERROR |
 	       (send_bytes << DP_AUX_CH_CTL_MESSAGE_SIZE_SHIFT) |
-	       (3 << DP_AUX_CH_CTL_PRECHARGE_2US_SHIFT) |
+	       (g4x_dp_aux_precharge_len() << DP_AUX_CH_CTL_PRECHARGE_2US_SHIFT) |
 	       (aux_clock_divider << DP_AUX_CH_CTL_BIT_CLOCK_2X_SHIFT);
 }
 
@@ -166,8 +192,8 @@  static u32 skl_get_aux_send_ctl(struct intel_dp *intel_dp,
 	      DP_AUX_CH_CTL_TIME_OUT_MAX |
 	      DP_AUX_CH_CTL_RECEIVE_ERROR |
 	      (send_bytes << DP_AUX_CH_CTL_MESSAGE_SIZE_SHIFT) |
-	      DP_AUX_CH_CTL_FW_SYNC_PULSE_SKL(24) |
-	      DP_AUX_CH_CTL_SYNC_PULSE_SKL(32);
+	      DP_AUX_CH_CTL_FW_SYNC_PULSE_SKL(intel_dp_aux_fw_sync_len()) |
+	      DP_AUX_CH_CTL_SYNC_PULSE_SKL(intel_dp_aux_sync_len());
 
 	if (intel_tc_port_in_tbt_alt_mode(dig_port))
 		ret |= DP_AUX_CH_CTL_TBT_IO;