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authorThierry Reding <treding@nvidia.com>2013-12-09 11:47:55 +0100
committerThierry Reding <treding@nvidia.com>2014-02-26 17:21:34 +0100
commit516c0f7c0a608833cc01d3f5b2a357ee806b78a1 (patch)
tree2ba87f3b5c08202f106c753cf138b2eba991a126 /drivers/gpu/drm/drm_dp_helper.c
parent8d4adc6a5807ca51999421b4d6d4f193c95775ba (diff)
drm/dp: Add DisplayPort link helpers
Add a helper to probe a DP link (read out the supported DPCD revision, maximum rate, link count and capabilities) as well as power up the DP link and configure it accordingly. Reviewed-by: Alex Deucher <alexander.deucher@amd.com> Reviewed-by: Jani Nikula <jani.nikula@intel.com> Signed-off-by: Thierry Reding <treding@nvidia.com> --- Changes in v5: - export helpers Changes in v4: - fix a couple of typos in comments as pointed out by Alex Deucher Changes in v3: - split into drm_dp_link_power_up() and drm_dp_link_configure() - do not change sink state for DPCD versions earlier than 1.1 - sleep for 1-2 ms after setting local sink to D0 state - read and write consecutive registers where possible - read DPCD revision when link is probed - remove duplicate kerneldoc
Diffstat (limited to 'drivers/gpu/drm/drm_dp_helper.c')
-rw-r--r--drivers/gpu/drm/drm_dp_helper.c97
1 files changed, 97 insertions, 0 deletions
diff --git a/drivers/gpu/drm/drm_dp_helper.c b/drivers/gpu/drm/drm_dp_helper.c
index 84262ed64ce..177ac7bd185 100644
--- a/drivers/gpu/drm/drm_dp_helper.c
+++ b/drivers/gpu/drm/drm_dp_helper.c
@@ -472,3 +472,100 @@ int drm_dp_dpcd_read_link_status(struct drm_dp_aux *aux,
DP_LINK_STATUS_SIZE);
}
EXPORT_SYMBOL(drm_dp_dpcd_read_link_status);
+
+/**
+ * drm_dp_link_probe() - probe a DisplayPort link for capabilities
+ * @aux: DisplayPort AUX channel
+ * @link: pointer to structure in which to return link capabilities
+ *
+ * The structure filled in by this function can usually be passed directly
+ * into drm_dp_link_power_up() and drm_dp_link_configure() to power up and
+ * configure the link based on the link's capabilities.
+ *
+ * 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)
+{
+ u8 values[3];
+ int err;
+
+ memset(link, 0, sizeof(*link));
+
+ err = drm_dp_dpcd_read(aux, DP_DPCD_REV, values, sizeof(values));
+ if (err < 0)
+ return err;
+
+ link->revision = values[0];
+ link->rate = drm_dp_bw_code_to_link_rate(values[1]);
+ link->num_lanes = values[2] & DP_MAX_LANE_COUNT_MASK;
+
+ if (values[2] & DP_ENHANCED_FRAME_CAP)
+ link->capabilities |= DP_LINK_CAP_ENHANCED_FRAMING;
+
+ return 0;
+}
+EXPORT_SYMBOL(drm_dp_link_probe);
+
+/**
+ * drm_dp_link_power_up() - power up a DisplayPort link
+ * @aux: DisplayPort AUX channel
+ * @link: pointer to a structure containing the link configuration
+ *
+ * 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)
+{
+ u8 value;
+ int err;
+
+ /* DP_SET_POWER register is only available on DPCD v1.1 and later */
+ if (link->revision < 0x11)
+ return 0;
+
+ 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, DP_SET_POWER, value);
+ if (err < 0)
+ return err;
+
+ /*
+ * According to the DP 1.1 specification, a "Sink Device must exit the
+ * power saving state within 1 ms" (Section 2.5.3.1, Table 5-52, "Sink
+ * Control Field" (register 0x600).
+ */
+ usleep_range(1000, 2000);
+
+ return 0;
+}
+EXPORT_SYMBOL(drm_dp_link_power_up);
+
+/**
+ * drm_dp_link_configure() - configure a DisplayPort link
+ * @aux: DisplayPort AUX channel
+ * @link: pointer to a structure containing the link configuration
+ *
+ * Returns 0 on success or a negative error code on failure.
+ */
+int drm_dp_link_configure(struct drm_dp_aux *aux, struct drm_dp_link *link)
+{
+ u8 values[2];
+ int err;
+
+ values[0] = drm_dp_link_rate_to_bw_code(link->rate);
+ values[1] = link->num_lanes;
+
+ if (link->capabilities & DP_LINK_CAP_ENHANCED_FRAMING)
+ values[1] |= DP_LANE_COUNT_ENHANCED_FRAME_EN;
+
+ err = drm_dp_dpcd_write(aux, DP_LINK_BW_SET, values, sizeof(values));
+ if (err < 0)
+ return err;
+
+ return 0;
+}
+EXPORT_SYMBOL(drm_dp_link_configure);