drm/radeon: workaround a hw bug on some radeon chipsets with all-0 EDIDs.

Some RS690 chipsets seem to end up with floating connectors, either
a DVI connector isn't actually populated, or an add-in HDMI card
is available but not installed. In this case we seem to get a NULL byte
response for each byte of the i2c transaction, so we detect this
case and if we see it we don't do anymore DDC transactions on this
connector.

I've tested this on my RS690 without the HDMI card installed and
it seems to work fine.

Signed-off-by: Dave Airlie <airlied@redhat.com>
Reviewed-by: Alex Deucher <alexdeucher@gmail.com>

diff --git a/drivers/gpu/drm/drm_edid.c b/drivers/gpu/drm/drm_edid.c
index 3618d29c79a24d2404688a11b5964aac06ecd451..09292193dafe0b28466e37061acc7bee25e348f5 100644 (file)
--- a/drivers/gpu/drm/drm_edid.c
+++ b/drivers/gpu/drm/drm_edid.c
@@ -258,6 +258,17 @@ drm_do_probe_ddc_edid(struct i2c_adapter *adapter, unsigned char *buf,
        return ret == 2 ? 0 : -1;
 }
 
+static bool drm_edid_is_zero(u8 *in_edid, int length)
+{
+       int i;
+       u32 *raw_edid = (u32 *)in_edid;
+
+       for (i = 0; i < length / 4; i++)
+               if (*(raw_edid + i) != 0)
+                       return false;
+       return true;
+}
+
 static u8 *
 drm_do_get_edid(struct drm_connector *connector, struct i2c_adapter *adapter)
 {
@@ -273,6 +284,10 @@ drm_do_get_edid(struct drm_connector *connector, struct i2c_adapter *adapter)
                        goto out;
                if (drm_edid_block_valid(block))
                        break;
+               if (i == 0 && drm_edid_is_zero(block, EDID_LENGTH)) {
+                       connector->null_edid_counter++;
+                       goto carp;
+               }
        }
        if (i == 4)
                goto carp;

diff --git a/drivers/gpu/drm/radeon/radeon_connectors.c b/drivers/gpu/drm/radeon/radeon_connectors.c
index 9c2929c7e79f9cf3390a8171416eab8d312148fa..c04e18ee8a8774c495ed187d0b3a3f828178cb22 100644 (file)
--- a/drivers/gpu/drm/radeon/radeon_connectors.c
+++ b/drivers/gpu/drm/radeon/radeon_connectors.c
@@ -836,6 +836,13 @@ radeon_dvi_detect(struct drm_connector *connector, bool force)
                if (!radeon_connector->edid) {
                        DRM_ERROR("%s: probed a monitor but no|invalid EDID\n",
                                        drm_get_connector_name(connector));
+                       /* rs690 seems to have a problem with connectors not existing and always
+                        * return a block of 0's. If we see this just stop polling on this output */
+                       if ((rdev->family == CHIP_RS690 || rdev->family == CHIP_RS740) && radeon_connector->base.null_edid_counter) {
+                               ret = connector_status_disconnected;
+                               DRM_ERROR("%s: detected RS690 floating bus bug, stopping ddc detect\n", drm_get_connector_name(connector));
+                               radeon_connector->ddc_bus = NULL;
+                       }
                } else {
                        radeon_connector->use_digital = !!(radeon_connector->edid->input & DRM_EDID_INPUT_DIGITAL);
 

diff --git a/include/drm/drm_crtc.h b/include/drm/drm_crtc.h
index 9573e0ce312080caf9bcbcb72cd804e2ed200871..33d12f87f0e01735d41a800a73b7ea5ddc9b31a6 100644 (file)
--- a/include/drm/drm_crtc.h
+++ b/include/drm/drm_crtc.h
@@ -520,6 +520,8 @@ struct drm_connector {
        uint32_t encoder_ids[DRM_CONNECTOR_MAX_ENCODER];
        uint32_t force_encoder_id;
        struct drm_encoder *encoder; /* currently active encoder */
+
+       int null_edid_counter; /* needed to workaround some HW bugs where we get all 0s */
 };
 
 /**