diff options
Diffstat (limited to 'drivers/gpu/drm/dp/drm_dp.c')
| -rw-r--r-- | drivers/gpu/drm/dp/drm_dp.c | 33 |
1 files changed, 28 insertions, 5 deletions
diff --git a/drivers/gpu/drm/dp/drm_dp.c b/drivers/gpu/drm/dp/drm_dp.c index 580016a1b9eb..2a1f5ff6633c 100644 --- a/drivers/gpu/drm/dp/drm_dp.c +++ b/drivers/gpu/drm/dp/drm_dp.c @@ -528,6 +528,31 @@ unlock: } /** + * drm_dp_dpcd_probe() - probe a given DPCD address with a 1-byte read access + * @aux: DisplayPort AUX channel (SST) + * @offset: address of the register to probe + * + * Probe the provided DPCD address by reading 1 byte from it. The function can + * be used to trigger some side-effect the read access has, like waking up the + * sink, without the need for the read-out value. + * + * Returns 0 if the read access suceeded, or a negative error code on failure. + */ +int drm_dp_dpcd_probe(struct drm_dp_aux *aux, unsigned int offset) +{ + u8 buffer; + int ret; + + ret = drm_dp_dpcd_access(aux, DP_AUX_NATIVE_READ, offset, &buffer, 1); + WARN_ON(ret == 0); + + drm_dp_dump_access(aux, DP_AUX_NATIVE_READ, offset, &buffer, ret); + + return ret < 0 ? ret : 0; +} +EXPORT_SYMBOL(drm_dp_dpcd_probe); + +/** * drm_dp_dpcd_read() - read a series of bytes from the DPCD * @aux: DisplayPort AUX channel (SST or MST) * @offset: address of the (first) register to read @@ -559,10 +584,9 @@ ssize_t drm_dp_dpcd_read(struct drm_dp_aux *aux, unsigned int offset, * monitor doesn't power down exactly after the throw away read. */ if (!aux->is_remote) { - ret = drm_dp_dpcd_access(aux, DP_AUX_NATIVE_READ, DP_DPCD_REV, - buffer, 1); - if (ret != 1) - goto out; + ret = drm_dp_dpcd_probe(aux, DP_DPCD_REV); + if (ret < 0) + return ret; } if (aux->is_remote) @@ -571,7 +595,6 @@ ssize_t drm_dp_dpcd_read(struct drm_dp_aux *aux, unsigned int offset, ret = drm_dp_dpcd_access(aux, DP_AUX_NATIVE_READ, offset, buffer, size); -out: drm_dp_dump_access(aux, DP_AUX_NATIVE_READ, offset, buffer, ret); return ret; } |