[PATCH 1/2] Give up on edid retries when i2c tells us that bus is not there

[Eugeni Dodonov]

This allows to avoid talking to a non-existent bus repeatedly until we
finally timeout. The non-existent bus is signalled by -ENXIO error,
provided by i2c_algo_bit:bit_doAddress call.

As the advantage of such change, all the other routines which use
drm_get_edid would benefit for this timeout.

This change should fix
https://bugs.freedesktop.org/show_bug.cgi?id=41059 and improve overall
edid detection timing by 10-30% in most cases, and by a much larger margin
in case of phantom outputs.

Signed-off-by: Eugeni Dodonov <eugeni.dodonov at intel.com>
---
 drivers/gpu/drm/drm_edid.c |    5 +++++
 1 files changed, 5 insertions(+), 0 deletions(-)

diff --git a/drivers/gpu/drm/drm_edid.c b/drivers/gpu/drm/drm_edid.c
index 7425e5c..1bca6d7 100644
--- a/drivers/gpu/drm/drm_edid.c
+++ b/drivers/gpu/drm/drm_edid.c
@@ -265,6 +265,11 @@ drm_do_probe_ddc_edid(struct i2c_adapter *adapter, unsigned char *buf,
 			}
 		};
 		ret = i2c_transfer(adapter, msgs, 2);
+		if (ret == -ENXIO) {
+			DRM_DEBUG_KMS("drm: skipping non-existent adapter %s\n",
+					adapter->name);
+			break;
+		}
 	} while (ret != 2 && --retries);
 
 	return ret == 2 ? 0 : -1;
-- 
1.7.7