[PATCH 02/10] drm/i915: Add counters in the drm_dp_aux struct for I2C NACKs and DEFERs

[Todd Previte]

These counters are used for Displayort compliance testing to detect error
conditions when executing tests 4.2.2.4 and 4.2.2.5 in the Displayport Link
CTS specificaiton. They determine whether to use the preferred/requested
mode or the failsafe mode during these tests.

V2:
- Addressed previous review feedback
- Updated commit message
- Changed from uint8_t to uint32_t

Cc: dri-devel at lists.freedesktop.org
Signed-off-by: Todd Previte <tprevite at gmail.com>
---
 drivers/gpu/drm/drm_dp_helper.c | 2 ++
 include/drm/drm_dp_helper.h     | 1 +
 2 files changed, 3 insertions(+)

diff --git a/drivers/gpu/drm/drm_dp_helper.c b/drivers/gpu/drm/drm_dp_helper.c
index 08e33b8..8353051 100644
--- a/drivers/gpu/drm/drm_dp_helper.c
+++ b/drivers/gpu/drm/drm_dp_helper.c
@@ -654,10 +654,12 @@ static int drm_dp_i2c_do_msg(struct drm_dp_aux *aux, struct drm_dp_aux_msg *msg)
 
 		case DP_AUX_I2C_REPLY_NACK:
 			DRM_DEBUG_KMS("I2C nack\n");
+			aux->i2c_nack_count++;
 			return -EREMOTEIO;
 
 		case DP_AUX_I2C_REPLY_DEFER:
 			DRM_DEBUG_KMS("I2C defer\n");
+			aux->i2c_defer_count++;
 			usleep_range(400, 500);
 			continue;
 
diff --git a/include/drm/drm_dp_helper.h b/include/drm/drm_dp_helper.h
index 8edeed0..23082ce 100644
--- a/include/drm/drm_dp_helper.h
+++ b/include/drm/drm_dp_helper.h
@@ -551,6 +551,7 @@ struct drm_dp_aux {
 	struct mutex hw_mutex;
 	ssize_t (*transfer)(struct drm_dp_aux *aux,
 			    struct drm_dp_aux_msg *msg);
+	uint32_t i2c_nack_count, i2c_defer_count;
 };
 
 ssize_t drm_dp_dpcd_read(struct drm_dp_aux *aux, unsigned int offset,
-- 
1.9.1