drm/i915/crt: Use a DDC probe on 0xA0 before load-detect
The BIOS writer's guide suggests that a VGA connection will ACK a write
to address 0xA0 and that this should be used before doing legacy
load-detection. Considering the extreme cost of load-detection,
performing an extra DDC seems a risk worth taking.
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
diff --git a/drivers/gpu/drm/i915/intel_crt.c b/drivers/gpu/drm/i915/intel_crt.c
index 8e484c9..389fcd2 100644
--- a/drivers/gpu/drm/i915/intel_crt.c
+++ b/drivers/gpu/drm/i915/intel_crt.c
@@ -261,6 +261,21 @@
return ret;
}
+static bool intel_crt_ddc_probe(struct drm_i915_private *dev_priv, int ddc_bus)
+{
+ u8 buf;
+ struct i2c_msg msgs[] = {
+ {
+ .addr = 0xA0,
+ .flags = 0,
+ .len = 1,
+ .buf = &buf,
+ },
+ };
+ /* DDC monitor detect: Does it ACK a write to 0xA0? */
+ return i2c_transfer(&dev_priv->gmbus[ddc_bus].adapter, msgs, 1) == 1;
+}
+
static bool intel_crt_detect_ddc(struct drm_encoder *encoder)
{
struct intel_encoder *intel_encoder = to_intel_encoder(encoder);
@@ -270,7 +285,17 @@
if (intel_encoder->type != INTEL_OUTPUT_ANALOG)
return false;
- return intel_ddc_probe(intel_encoder, dev_priv->crt_ddc_pin);
+ if (intel_crt_ddc_probe(dev_priv, dev_priv->crt_ddc_pin)) {
+ DRM_DEBUG_KMS("CRT detected via DDC:0xa0\n");
+ return true;
+ }
+
+ if (intel_ddc_probe(intel_encoder, dev_priv->crt_ddc_pin)) {
+ DRM_DEBUG_KMS("CRT detected via DDC:0x50 [EDID]\n");
+ return true;
+ }
+
+ return false;
}
static enum drm_connector_status
@@ -296,6 +321,8 @@
uint8_t st00;
enum drm_connector_status status;
+ DRM_DEBUG_KMS("starting load-detect on CRT\n");
+
if (pipe == 0) {
bclrpat_reg = BCLRPAT_A;
vtotal_reg = VTOTAL_A;
@@ -412,9 +439,10 @@
enum drm_connector_status status;
if (I915_HAS_HOTPLUG(dev)) {
- if (intel_crt_detect_hotplug(connector))
+ if (intel_crt_detect_hotplug(connector)) {
+ DRM_DEBUG_KMS("CRT detected via hotplug\n");
return connector_status_connected;
- else
+ } else
return connector_status_disconnected;
}
@@ -431,7 +459,10 @@
crtc = intel_get_load_detect_pipe(encoder, connector,
NULL, &dpms_mode);
if (crtc) {
- status = intel_crt_load_detect(crtc, encoder);
+ if (intel_crt_detect_ddc(&encoder->base))
+ status = connector_status_connected;
+ else
+ status = intel_crt_load_detect(crtc, encoder);
intel_release_load_detect_pipe(encoder,
connector, dpms_mode);
} else