Add a helper to probe a DP link (reading out the maximum rate, link
count and capabilities) as well as configuring it accordingly.
Signed-off-by: Thierry Reding <treding@xxxxxxxxxx>
---
drivers/gpu/drm/drm_dp_helper.c | 59 +++++++++++++++++++++++++++++++++++++++++
include/drm/drm_dp_helper.h | 30 +++++++++++++++++++++
2 files changed, 89 insertions(+)
diff --git a/drivers/gpu/drm/drm_dp_helper.c b/drivers/gpu/drm/drm_dp_helper.c
index d7a4df2e6b56..873aedccc84e 100644
--- a/drivers/gpu/drm/drm_dp_helper.c
+++ b/drivers/gpu/drm/drm_dp_helper.c
@@ -412,3 +412,62 @@ int drm_dp_dpcd_read_link_status(struct drm_dp_aux *aux,
DP_LINK_STATUS_SIZE);
}
EXPORT_SYMBOL(drm_dp_dpcd_read_link_status);
+
+int drm_dp_link_probe(struct drm_dp_aux *aux, struct drm_dp_link *link)
+{
+ u8 value;
+ int err;
+
+ memset(link, 0, sizeof(*link));
+
+ err = drm_dp_dpcd_readb(aux, DP_MAX_LINK_RATE, &value);
+ if (err < 0)
+ return err;
+
+ link->rate = drm_dp_bw_code_to_link_rate(value);
+
+ err = drm_dp_dpcd_readb(aux, DP_MAX_LANE_COUNT, &value);
+ if (err < 0)
+ return err;
+
+ link->num_lanes = value & DP_MAX_LANE_COUNT_MASK;
+
+ if (value & DP_ENHANCED_FRAME_CAP)
+ link->capabilities |= DP_LINK_CAP_ENHANCED_FRAMING;
+
+ return 0;
+}
+
+int drm_dp_link_power_up(struct drm_dp_aux *aux, struct drm_dp_link *link)
+{
+ u8 value;
+ int err;
+
+ err = drm_dp_dpcd_readb(aux, DP_SET_POWER, &value);
+ if (err < 0)
+ return err;
+
+ value &= ~DP_SET_POWER_MASK;
+ value |= DP_SET_POWER_D0;
+
+ err = drm_dp_dpcd_writeb(aux, value, DP_SET_POWER);
+ if (err < 0)
+ return err;
+
+ value = drm_dp_link_rate_to_bw_code(link->rate);
+
+ err = drm_dp_dpcd_writeb(aux, value, DP_LINK_BW_SET);
+ if (err < 0)
+ return err;
+
+ value = link->num_lanes;
+
+ if (link->capabilities & DP_LINK_CAP_ENHANCED_FRAMING)
+ value |= DP_LANE_COUNT_ENHANCED_FRAME_EN;
+
+ err = drm_dp_dpcd_writeb(aux, value, DP_LANE_COUNT_SET);
+ if (err < 0)
+ return err;
+
+ return 0;
+}
diff --git a/include/drm/drm_dp_helper.h b/include/drm/drm_dp_helper.h
index a7c336444cea..cf03a6ff8634 100644
--- a/include/drm/drm_dp_helper.h
+++ b/include/drm/drm_dp_helper.h
@@ -290,6 +290,7 @@
#define DP_SET_POWER 0x600
# define DP_SET_POWER_D0 0x1
# define DP_SET_POWER_D3 0x2
+# define DP_SET_POWER_MASK 0x3
#define DP_PSR_ERROR_STATUS 0x2006 /* XXX 1.2? */
# define DP_PSR_LINK_CRC_ERROR (1 << 0)
@@ -485,4 +486,33 @@ static inline ssize_t drm_dp_dpcd_writeb(struct drm_dp_aux *aux, u8 value,
int drm_dp_dpcd_read_link_status(struct drm_dp_aux *aux,
u8 status[DP_LINK_STATUS_SIZE]);
+/*
+ * DisplayPort link
+ */
+#define DP_LINK_CAP_ENHANCED_FRAMING (1 << 0)
+
+struct drm_dp_link {
+ unsigned int rate;
+ unsigned int num_lanes;
+ unsigned long capabilities;
+};
+
+/**
+ * drm_dp_link_probe() - probe link properties and capabilities
+ * @aux: DisplayPort AUX channel
+ * @link: DisplayPort link
+ *
+ * Returns 0 on success or a negative error code on failure.
+ */
+int drm_dp_link_probe(struct drm_dp_aux *aux, struct drm_dp_link *link);
+
+/**
+ * drm_dp_link_power_up() - power up a link
+ * @aux: DisplayPort AUX channel
+ * @link: DisplayPort link
+ *
+ * Returns 0 on success or a negative error code on failure.
+ */
+int drm_dp_link_power_up(struct drm_dp_aux *aux, struct drm_dp_link *link);
+
#endif /* _DRM_DP_HELPER_H_ */
--
1.8.4.2
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