| Message ID | 20220411132539.984647-1-imre.deak@intel.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [v3,1/2] drm/dp: Factor out a function to probe a DPCD address | expand |
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,
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,
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. 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> --- drivers/gpu/drm/dp/drm_dp.c | 33 ++++++++++++++++++++++++++++----- include/drm/dp/drm_dp_helper.h | 1 + 2 files changed, 29 insertions(+), 5 deletions(-)