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path: root/drivers/gpu/drm/drm_dp_dual_mode_helper.c
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Diffstat (limited to 'drivers/gpu/drm/drm_dp_dual_mode_helper.c')
-rw-r--r--drivers/gpu/drm/drm_dp_dual_mode_helper.c39
1 files changed, 32 insertions, 7 deletions
diff --git a/drivers/gpu/drm/drm_dp_dual_mode_helper.c b/drivers/gpu/drm/drm_dp_dual_mode_helper.c
index 02a50929af67..e7f4fe2848a5 100644
--- a/drivers/gpu/drm/drm_dp_dual_mode_helper.c
+++ b/drivers/gpu/drm/drm_dp_dual_mode_helper.c
@@ -350,19 +350,44 @@ int drm_dp_dual_mode_set_tmds_output(enum drm_dp_dual_mode_type type,
{
uint8_t tmds_oen = enable ? 0 : DP_DUAL_MODE_TMDS_DISABLE;
ssize_t ret;
+ int retry;
if (type < DRM_DP_DUAL_MODE_TYPE2_DVI)
return 0;
- ret = drm_dp_dual_mode_write(adapter, DP_DUAL_MODE_TMDS_OEN,
- &tmds_oen, sizeof(tmds_oen));
- if (ret) {
- DRM_DEBUG_KMS("Failed to %s TMDS output buffers\n",
- enable ? "enable" : "disable");
- return ret;
+ /*
+ * LSPCON adapters in low-power state may ignore the first write, so
+ * read back and verify the written value a few times.
+ */
+ for (retry = 0; retry < 3; retry++) {
+ uint8_t tmp;
+
+ ret = drm_dp_dual_mode_write(adapter, DP_DUAL_MODE_TMDS_OEN,
+ &tmds_oen, sizeof(tmds_oen));
+ if (ret) {
+ DRM_DEBUG_KMS("Failed to %s TMDS output buffers (%d attempts)\n",
+ enable ? "enable" : "disable",
+ retry + 1);
+ return ret;
+ }
+
+ ret = drm_dp_dual_mode_read(adapter, DP_DUAL_MODE_TMDS_OEN,
+ &tmp, sizeof(tmp));
+ if (ret) {
+ DRM_DEBUG_KMS("I2C read failed during TMDS output buffer %s (%d attempts)\n",
+ enable ? "enabling" : "disabling",
+ retry + 1);
+ return ret;
+ }
+
+ if (tmp == tmds_oen)
+ return 0;
}
- return 0;
+ DRM_DEBUG_KMS("I2C write value mismatch during TMDS output buffer %s\n",
+ enable ? "enabling" : "disabling");
+
+ return -EIO;
}
EXPORT_SYMBOL(drm_dp_dual_mode_set_tmds_output);