Merge tag 'asm-generic-4.7' of git://git.kernel.org/pub/scm/linux/kernel/git/arnd...

[karo-tx-linux.git] / drivers / gpu / drm / drm_dp_helper.c

diff --git a/drivers/gpu/drm/drm_dp_helper.c b/drivers/gpu/drm/drm_dp_helper.c
index df64ed1c0139e9213912e0f05043489ce6f0d0ba..eeaf5a7c3aa767a6676b9b6054a020b3fea87445 100644 (file)
--- a/drivers/gpu/drm/drm_dp_helper.c
+++ b/drivers/gpu/drm/drm_dp_helper.c
@@ -178,8 +178,8 @@ static int drm_dp_dpcd_access(struct drm_dp_aux *aux, u8 request,
                              unsigned int offset, void *buffer, size_t size)
 {
        struct drm_dp_aux_msg msg;
-       unsigned int retry;
-       int err = 0;
+       unsigned int retry, native_reply;
+       int err = 0, ret = 0;
 
        memset(&msg, 0, sizeof(msg));
        msg.address = offset;
@@ -196,38 +196,39 @@ static int drm_dp_dpcd_access(struct drm_dp_aux *aux, u8 request,
         * sufficient, bump to 32 which makes Dell 4k monitors happier.
         */
        for (retry = 0; retry < 32; retry++) {
-
-               err = aux->transfer(aux, &msg);
-               if (err < 0) {
-                       if (err == -EBUSY)
-                               continue;
-
-                       goto unlock;
+               if (ret != 0 && ret != -ETIMEDOUT) {
+                       usleep_range(AUX_RETRY_INTERVAL,
+                                    AUX_RETRY_INTERVAL + 100);
                }
 
+               ret = aux->transfer(aux, &msg);
 
-               switch (msg.reply & DP_AUX_NATIVE_REPLY_MASK) {
-               case DP_AUX_NATIVE_REPLY_ACK:
-                       if (err < size)
-                               err = -EPROTO;
-                       goto unlock;
+               if (ret > 0) {
+                       native_reply = msg.reply & DP_AUX_NATIVE_REPLY_MASK;
+                       if (native_reply == DP_AUX_NATIVE_REPLY_ACK) {
+                               if (ret == size)
+                                       goto unlock;
 
-               case DP_AUX_NATIVE_REPLY_NACK:
-                       err = -EIO;
-                       goto unlock;
-
-               case DP_AUX_NATIVE_REPLY_DEFER:
-                       usleep_range(AUX_RETRY_INTERVAL, AUX_RETRY_INTERVAL + 100);
-                       break;
+                               ret = -EPROTO;
+                       } else
+                               ret = -EIO;
                }
+
+               /*
+                * We want the error we return to be the error we received on
+                * the first transaction, since we may get a different error the
+                * next time we retry
+                */
+               if (!err)
+                       err = ret;
        }
 
        DRM_DEBUG_KMS("too many retries, giving up\n");
-       err = -EIO;
+       ret = err;
 
 unlock:
        mutex_unlock(&aux->hw_mutex);
-       return err;
+       return ret;
 }
 
 /**
@@ -247,6 +248,25 @@ unlock:
 ssize_t drm_dp_dpcd_read(struct drm_dp_aux *aux, unsigned int offset,
                         void *buffer, size_t size)
 {
+       int ret;
+
+       /*
+        * HP ZR24w corrupts the first DPCD access after entering power save
+        * mode. Eg. on a read, the entire buffer will be filled with the same
+        * byte. Do a throw away read to avoid corrupting anything we care
+        * about. Afterwards things will work correctly until the monitor
+        * gets woken up and subsequently re-enters power save mode.
+        *
+        * The user pressing any button on the monitor is enough to wake it
+        * up, so there is no particularly good place to do the workaround.
+        * We just have to do it before any DPCD access and hope that the
+        * monitor doesn't power down exactly after the throw away read.
+        */
+       ret = drm_dp_dpcd_access(aux, DP_AUX_NATIVE_READ, DP_DPCD_REV, buffer,
+                                1);
+       if (ret != 1)
+               return ret;
+
        return drm_dp_dpcd_access(aux, DP_AUX_NATIVE_READ, offset, buffer,
                                  size);
 }