Filter out a mode that exceeds the max pixel rate setting
for DP to VGA dongle. This is defined in DPCD register 0x81
if detailed cap info i.e. info field is 4 bytes long and
it is available for DP downstream port.
The register defines the pixel rate divided by 8 in MP/s.
v2: DPCD read outs and computation moved to drm (Ville, Daniel)
v3: Sink pixel rate computation moved to drm_dp_max_sink_dotclock()
function (Daniel)
v4: Use of drm_dp_helper.c routines to compute max pixel clock (Ville)
v5: Use of intel_dp->downstream_ports to read out port capabilities.
Code restructuring (Ville)
Signed-off-by: Mika Kahola <mika.kahola@xxxxxxxxx>
---
drivers/gpu/drm/i915/intel_dp.c | 26 ++++++++++++++++++++++++++
1 file changed, 26 insertions(+)
diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
index f97cd53..3b09230 100644
--- a/drivers/gpu/drm/i915/intel_dp.c
+++ b/drivers/gpu/drm/i915/intel_dp.c
@@ -190,6 +190,20 @@ intel_dp_max_data_rate(int max_link_clock, int max_lanes)
return (max_link_clock * max_lanes * 8) / 10;
}
+static int
+intel_dp_downstream_max_clock(struct intel_dp *intel_dp, int clock)
+{
+ int dp_ds_clk;
+
+ dp_ds_clk = drm_dp_downstream_max_clock(intel_dp->dpcd,
+ intel_dp->downstream_ports);
+
+ if (dp_ds_clk == 0)
+ return clock;
+
+ return min(clock, dp_ds_clk);
+}
+
static enum drm_mode_status
intel_dp_mode_valid(struct drm_connector *connector,
struct drm_display_mode *mode)
@@ -201,6 +215,18 @@ intel_dp_mode_valid(struct drm_connector *connector,
int max_rate, mode_rate, max_lanes, max_link_clock;
int max_dotclk = to_i915(connector->dev)->max_dotclk_freq;
+ bool is_branch_device = intel_dp->dpcd[DP_DOWNSTREAMPORT_PRESENT] &
+ DP_DWN_STRM_PORT_PRESENT;
+ int type;
+
+ if (is_branch_device) {
+ type = intel_dp->downstream_ports[0] & DP_DS_PORT_TYPE_MASK;
+
+ if (type == DP_DS_PORT_TYPE_VGA)
+ max_dotclk = intel_dp_downstream_max_clock(intel_dp,
+ max_dotclk);
+ }
+
if (is_edp(intel_dp) && fixed_mode) {
if (mode->hdisplay > fixed_mode->hdisplay)
return MODE_PANEL;
--
1.9.1
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