On Mon, 11 Apr 2022, Imre Deak imre.deak@intel.com wrote:
Factor out from drm_dp_dpcd_read() a function to probe a DPCD address with a 1-byte read access. This will be needed by the next patch doing a read from an LTTPR address, which must happen without the preceding wake-up read in drm_dp_dpcd_read().
While at it add tracing for the 1 byte read even if the read was successful.
Let's see if that's going to be annoying and confusing...
v2: Add a probe function instead of exporting drm_dp_dpcd_access(). (Jani) v3: Add tracing for the 1-byte read even if the read was successful. (Khaled)
Cc: Jani Nikula jani.nikula@linux.intel.com Cc: Khaled Almahallawy khaled.almahallawy@intel.com Cc: dri-devel@lists.freedesktop.org Signed-off-by: Imre Deak imre.deak@intel.com
Reviewed-by: Jani Nikula jani.nikula@intel.com
drivers/gpu/drm/dp/drm_dp.c | 33 ++++++++++++++++++++++++++++----- include/drm/dp/drm_dp_helper.h | 1 + 2 files changed, 29 insertions(+), 5 deletions(-)
diff --git a/drivers/gpu/drm/dp/drm_dp.c b/drivers/gpu/drm/dp/drm_dp.c index 580016a1b9eb7..2a1f5ff6633cc 100644 --- a/drivers/gpu/drm/dp/drm_dp.c +++ b/drivers/gpu/drm/dp/drm_dp.c @@ -527,6 +527,31 @@ static int drm_dp_dpcd_access(struct drm_dp_aux *aux, u8 request, return ret; }
+/**
- 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)
@@ -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; } diff --git a/include/drm/dp/drm_dp_helper.h b/include/drm/dp/drm_dp_helper.h index 1eccd97419436..91af98e6617c6 100644 --- a/include/drm/dp/drm_dp_helper.h +++ b/include/drm/dp/drm_dp_helper.h @@ -2053,6 +2053,7 @@ struct drm_dp_aux { bool is_remote; };
+int drm_dp_dpcd_probe(struct drm_dp_aux *aux, unsigned int offset); ssize_t drm_dp_dpcd_read(struct drm_dp_aux *aux, unsigned int offset, void *buffer, size_t size); ssize_t drm_dp_dpcd_write(struct drm_dp_aux *aux, unsigned int offset,