[Intel-gfx] [PATCH 1/2] drm: add retries for lspcon status check

Shashank Sharma shashank.sharma at intel.com
Fri Aug 11 13:28:26 UTC 2017


It's an observation during some CI tests that few LSPCON chips
respond slow while system is under load, and need some delay
while reading current mode status using i2c-over-aux channel.

This patch:
- Adds few retries and delays before declaring a read
  failure from LSPCON hardware.
- Changes the debug level of the print from ERROR->DEBUG
  whereas another patch in I915 will add an ERROR message
  from the caller when we have timed out all our limits.

Cc: Ville Syrjala <ville.syrjala at linux.intel.com>
Cc: Imre Deak <imre.deak at intel.com>
Signed-off-by: Shashank Sharma <shashank.sharma at intel.com>
Signed-off-by: Mahesh Kumar <mahesh1.kumar at intel.com>
---
 drivers/gpu/drm/drm_dp_dual_mode_helper.c | 14 +++++++++++---
 1 file changed, 11 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/drm_dp_dual_mode_helper.c b/drivers/gpu/drm/drm_dp_dual_mode_helper.c
index 80e62f6..c63eac8 100644
--- a/drivers/gpu/drm/drm_dp_dual_mode_helper.c
+++ b/drivers/gpu/drm/drm_dp_dual_mode_helper.c
@@ -409,6 +409,7 @@ int drm_lspcon_get_mode(struct i2c_adapter *adapter,
 			enum drm_lspcon_mode *mode)
 {
 	u8 data;
+	u8 retry = 5;
 	int ret = 0;
 
 	if (!mode) {
@@ -417,10 +418,17 @@ int drm_lspcon_get_mode(struct i2c_adapter *adapter,
 	}
 
 	/* Read Status: i2c over aux */
-	ret = drm_dp_dual_mode_read(adapter, DP_DUAL_MODE_LSPCON_CURRENT_MODE,
-				    &data, sizeof(data));
+	do {
+		ret = drm_dp_dual_mode_read(adapter,
+					    DP_DUAL_MODE_LSPCON_CURRENT_MODE,
+					    &data, sizeof(data));
+		if (!ret || !retry--)
+			break;
+		usleep_range(500, 1000);
+	} while (1);
+
 	if (ret < 0) {
-		DRM_ERROR("LSPCON read(0x80, 0x41) failed\n");
+		DRM_DEBUG_KMS("LSPCON read(0x80, 0x41) failed\n");
 		return -EFAULT;
 	}
 
-- 
2.7.4



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