drm/dp_helper: don't return EPROTO for defers (v2)

If we get a msg.reply of REPLY_DEFER, we also get an err of 0
so we fail reads with 0 < size and return -EPROTO instead of trying
again.

v2: same fix in i2c code.

Found writing MST support.

Reviewed-by: Jani Nikula <jani.nikula@intel.com>
Reviewed-by: Thierry Reding <treding@nvidia.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>

1 files changed, 4 insertions, 4 deletions

diff --git a/drivers/gpu/drm/drm_dp_helper.c b/drivers/gpu/drm/drm_dp_helper.c
index f4babed2f557..27671489477d 100644
--- a/drivers/gpu/drm/drm_dp_helper.c
+++ b/drivers/gpu/drm/drm_dp_helper.c
@@ -386,11 +386,11 @@ static int drm_dp_dpcd_access(struct drm_dp_aux *aux, u8 request,
                         return err;
                 }
 
-                if (err < size)
-                        return -EPROTO;
 
                 switch (msg.reply & DP_AUX_NATIVE_REPLY_MASK) {
                 case DP_AUX_NATIVE_REPLY_ACK:
+                        if (err < size)
+                                return -EPROTO;
                         return err;
 
                 case DP_AUX_NATIVE_REPLY_NACK:
@@ -599,8 +599,6 @@ static int drm_dp_i2c_do_msg(struct drm_dp_aux *aux, struct drm_dp_aux_msg *msg)
                         return err;
                 }
 
-                if (err < msg->size)
-                        return -EPROTO;
 
                 switch (msg->reply & DP_AUX_NATIVE_REPLY_MASK) {
                 case DP_AUX_NATIVE_REPLY_ACK:
@@ -639,6 +637,8 @@ static int drm_dp_i2c_do_msg(struct drm_dp_aux *aux, struct drm_dp_aux_msg *msg)
                          * Both native ACK and I2C ACK replies received. We
                          * can assume the transfer was successful.
                          */
+                        if (err < msg->size)
+                                return -EPROTO;
                         return 0;
 
                 case DP_AUX_I2C_REPLY_NACK: