From: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx>
Add helpers to get the TMDS clock limits for HDMI/DVI downstream
facing ports.
Signed-off-by: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx>
---
drivers/gpu/drm/drm_dp_helper.c | 116 ++++++++++++++++++++++++++++++++
include/drm/drm_dp_helper.h | 6 ++
2 files changed, 122 insertions(+)
diff --git a/drivers/gpu/drm/drm_dp_helper.c b/drivers/gpu/drm/drm_dp_helper.c
index 822a30e609ef..f567428f2aef 100644
--- a/drivers/gpu/drm/drm_dp_helper.c
+++ b/drivers/gpu/drm/drm_dp_helper.c
@@ -643,6 +643,114 @@ int drm_dp_downstream_max_dotclock(const u8 dpcd[DP_RECEIVER_CAP_SIZE],
}
EXPORT_SYMBOL(drm_dp_downstream_max_dotclock);
+/**
+ * drm_dp_downstream_max_tmds_clock() - extract downstream facing port max TMDS clock
+ * @dpcd: DisplayPort configuration data
+ * @port_cap: port capabilities
+ * @edid: EDID
+ *
+ * Returns HDMI/DVI downstream facing port max TMDS clock in kHz on success,
+ * or 0 if max TMDS clock not defined
+ */
+int drm_dp_downstream_max_tmds_clock(const u8 dpcd[DP_RECEIVER_CAP_SIZE],
+ const u8 port_cap[4],
+ const struct edid *edid)
+{
+ if (!drm_dp_is_branch(dpcd))
+ return 0;
+
+ if (dpcd[DP_DPCD_REV] < 0x11) {
+ switch (dpcd[DP_DOWNSTREAMPORT_PRESENT] & DP_DWN_STRM_PORT_TYPE_MASK) {
+ case DP_DWN_STRM_PORT_TYPE_TMDS:
+ return 165000;
+ default:
+ return 0;
+ }
+ }
+
+ switch (port_cap[0] & DP_DS_PORT_TYPE_MASK) {
+ case DP_DS_PORT_TYPE_DP_DUALMODE:
+ if (is_edid_digital_input_dp(edid))
+ return 0;
+ /*
+ * It's left up to the driver to check the
+ * DP dual mode adapter's max TMDS clock.
+ *
+ * Unfortunatley it looks like branch devices
+ * may not fordward that the DP dual mode i2c
+ * access so we just usually get i2c nak :(
+ */
+ fallthrough;
+ case DP_DS_PORT_TYPE_HDMI:
+ /*
+ * We should perhaps assume 165 MHz when detailed cap
+ * info is not available. But looks like many typical
+ * branch devices fall into that category and so we'd
+ * probably end up with users complaining that they can't
+ * get high resolution modes with their favorite dongle.
+ *
+ * So let's limit to 300 MHz instead since DPCD 1.4
+ * HDMI 2.0 DFPs are required to have the detailed cap
+ * info. So it's more likely we're dealing with a HDMI 1.4
+ * compatible* device here.
+ */
+ if ((dpcd[DP_DOWNSTREAMPORT_PRESENT] & DP_DETAILED_CAP_INFO_AVAILABLE) == 0)
+ return 300000;
+ return port_cap[1] * 2500;
+ case DP_DS_PORT_TYPE_DVI:
+ if ((dpcd[DP_DOWNSTREAMPORT_PRESENT] & DP_DETAILED_CAP_INFO_AVAILABLE) == 0)
+ return 165000;
+ /* FIXME what to do about DVI dual link? */
+ return port_cap[1] * 2500;
+ default:
+ return 0;
+ }
+}
+EXPORT_SYMBOL(drm_dp_downstream_max_tmds_clock);
+
+/**
+ * drm_dp_downstream_min_tmds_clock() - extract downstream facing port min TMDS clock
+ * @dpcd: DisplayPort configuration data
+ * @port_cap: port capabilities
+ * @edid: EDID
+ *
+ * Returns HDMI/DVI downstream facing port min TMDS clock in kHz on success,
+ * or 0 if max TMDS clock not defined
+ */
+int drm_dp_downstream_min_tmds_clock(const u8 dpcd[DP_RECEIVER_CAP_SIZE],
+ const u8 port_cap[4],
+ const struct edid *edid)
+{
+ if (!drm_dp_is_branch(dpcd))
+ return 0;
+
+ if (dpcd[DP_DPCD_REV] < 0x11) {
+ switch (dpcd[DP_DOWNSTREAMPORT_PRESENT] & DP_DWN_STRM_PORT_TYPE_MASK) {
+ case DP_DWN_STRM_PORT_TYPE_TMDS:
+ return 25000;
+ default:
+ return 0;
+ }
+ }
+
+ switch (port_cap[0] & DP_DS_PORT_TYPE_MASK) {
+ case DP_DS_PORT_TYPE_DP_DUALMODE:
+ if (is_edid_digital_input_dp(edid))
+ return 0;
+ fallthrough;
+ case DP_DS_PORT_TYPE_DVI:
+ case DP_DS_PORT_TYPE_HDMI:
+ /*
+ * Unclear whether the protocol converter could
+ * utilize pixel replication. Assume it won't.
+ */
+ return 25000;
+ default:
+ return 0;
+ }
+}
+EXPORT_SYMBOL(drm_dp_downstream_min_tmds_clock);
+
/**
* drm_dp_downstream_max_bpc() - extract downstream facing port max
* bits per component
@@ -788,6 +896,14 @@ void drm_dp_downstream_debug(struct seq_file *m,
if (clk > 0)
seq_printf(m, "\t\tMax dot clock: %d kHz\n", clk);
+ clk = drm_dp_downstream_max_tmds_clock(dpcd, port_cap, edid);
+ if (clk > 0)
+ seq_printf(m, "\t\tMax TMDS clock: %d kHz\n", clk);
+
+ clk = drm_dp_downstream_min_tmds_clock(dpcd, port_cap, edid);
+ if (clk > 0)
+ seq_printf(m, "\t\tMin TMDS clock: %d kHz\n", clk);
+
bpc = drm_dp_downstream_max_bpc(dpcd, port_cap, edid);
if (bpc > 0)
diff --git a/include/drm/drm_dp_helper.h b/include/drm/drm_dp_helper.h
index 19bc04207788..6812a3e0de8d 100644
--- a/include/drm/drm_dp_helper.h
+++ b/include/drm/drm_dp_helper.h
@@ -1645,6 +1645,12 @@ bool drm_dp_downstream_is_tmds(const u8 dpcd[DP_RECEIVER_CAP_SIZE],
const struct edid *edid);
int drm_dp_downstream_max_dotclock(const u8 dpcd[DP_RECEIVER_CAP_SIZE],
const u8 port_cap[4]);
+int drm_dp_downstream_max_tmds_clock(const u8 dpcd[DP_RECEIVER_CAP_SIZE],
+ const u8 port_cap[4],
+ const struct edid *edid);
+int drm_dp_downstream_min_tmds_clock(const u8 dpcd[DP_RECEIVER_CAP_SIZE],
+ const u8 port_cap[4],
+ const struct edid *edid);
int drm_dp_downstream_max_bpc(const u8 dpcd[DP_RECEIVER_CAP_SIZE],
const u8 port_cap[4],
const struct edid *edid);
--
2.26.2
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