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drm/dp: Factor out a function to probe a DPCD address
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> Reviewed-by: Jani Nikula <jani.nikula@intel.com> Link: https://patchwork.freedesktop.org/patch/msgid/20220411132539.984647-1-imre.deak@intel.com
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@ -527,6 +527,31 @@ unlock:
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return ret;
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}
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/**
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* drm_dp_dpcd_probe() - probe a given DPCD address with a 1-byte read access
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* @aux: DisplayPort AUX channel (SST)
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* @offset: address of the register to probe
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*
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* Probe the provided DPCD address by reading 1 byte from it. The function can
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* be used to trigger some side-effect the read access has, like waking up the
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* sink, without the need for the read-out value.
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*
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* Returns 0 if the read access suceeded, or a negative error code on failure.
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*/
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int drm_dp_dpcd_probe(struct drm_dp_aux *aux, unsigned int offset)
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{
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u8 buffer;
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int ret;
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ret = drm_dp_dpcd_access(aux, DP_AUX_NATIVE_READ, offset, &buffer, 1);
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WARN_ON(ret == 0);
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drm_dp_dump_access(aux, DP_AUX_NATIVE_READ, offset, &buffer, ret);
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return ret < 0 ? ret : 0;
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}
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EXPORT_SYMBOL(drm_dp_dpcd_probe);
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/**
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* drm_dp_dpcd_read() - read a series of bytes from the DPCD
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* @aux: DisplayPort AUX channel (SST or MST)
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@ -559,10 +584,9 @@ ssize_t drm_dp_dpcd_read(struct drm_dp_aux *aux, unsigned int offset,
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* monitor doesn't power down exactly after the throw away read.
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*/
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if (!aux->is_remote) {
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ret = drm_dp_dpcd_access(aux, DP_AUX_NATIVE_READ, DP_DPCD_REV,
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buffer, 1);
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if (ret != 1)
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goto out;
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ret = drm_dp_dpcd_probe(aux, DP_DPCD_REV);
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if (ret < 0)
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return ret;
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}
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if (aux->is_remote)
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@ -571,7 +595,6 @@ ssize_t drm_dp_dpcd_read(struct drm_dp_aux *aux, unsigned int offset,
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ret = drm_dp_dpcd_access(aux, DP_AUX_NATIVE_READ, offset,
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buffer, size);
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out:
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drm_dp_dump_access(aux, DP_AUX_NATIVE_READ, offset, buffer, ret);
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return ret;
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}
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@ -2053,6 +2053,7 @@ struct drm_dp_aux {
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bool is_remote;
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};
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int drm_dp_dpcd_probe(struct drm_dp_aux *aux, unsigned int offset);
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ssize_t drm_dp_dpcd_read(struct drm_dp_aux *aux, unsigned int offset,
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void *buffer, size_t size);
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ssize_t drm_dp_dpcd_write(struct drm_dp_aux *aux, unsigned int offset,
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