4 files changed, 80 insertions, 12 deletions

diff --git a/drivers/gpu/drm/radeon/radeon_connectors.c b/drivers/gpu/drm/radeon/radeon_connectors.c
index 9792d4ffdc86..6a0f1befbc15 100644
--- a/drivers/gpu/drm/radeon/radeon_connectors.c
+++ b/drivers/gpu/drm/radeon/radeon_connectors.c
@@ -430,6 +430,36 @@ int radeon_connector_set_property(struct drm_connector *connector, struct drm_pr
         return 0;
 }
 
+/*
+ * Some integrated ATI Radeon chipset implementations (e. g.
+ * Asus M2A-VM HDMI) may indicate the availability of a DDC,
+ * even when there's no monitor connected. For these connectors
+ * following DDC probe extension will be applied: check also for the
+ * availability of EDID with at least a correct EDID header. Only then,
+ * DDC is assumed to be available. This prevents drm_get_edid() and
+ * drm_edid_block_valid() from periodically dumping data and kernel
+ * errors into the logs and onto the terminal.
+ */
+static bool radeon_connector_needs_extended_probe(struct radeon_device *dev,
+                                     uint32_t supported_device,
+                                     int connector_type)
+{
+        /* Asus M2A-VM HDMI board sends data to i2c bus even,
+         * if HDMI add-on card is not plugged in or HDMI is disabled in
+         * BIOS. Valid DDC can only be assumed, if also a valid EDID header
+         * can be retrieved via i2c bus during DDC probe */
+        if ((dev->pdev->device == 0x791e) &&
+            (dev->pdev->subsystem_vendor == 0x1043) &&
+            (dev->pdev->subsystem_device == 0x826d)) {
+                if ((connector_type == DRM_MODE_CONNECTOR_HDMIA) &&
+                    (supported_device == ATOM_DEVICE_DFP2_SUPPORT))
+                        return true;
+        }
+
+        /* Default: no EDID header probe required for DDC probing */
+        return false;
+}
+
 static void radeon_fixup_lvds_native_mode(struct drm_encoder *encoder,
                                           struct drm_connector *connector)
 {
@@ -661,7 +691,8 @@ radeon_vga_detect(struct drm_connector *connector, bool force)
                 ret = connector_status_disconnected;
 
         if (radeon_connector->ddc_bus)
-                dret = radeon_ddc_probe(radeon_connector);
+                dret = radeon_ddc_probe(radeon_connector,
+                                        radeon_connector->requires_extended_probe);
         if (dret) {
                 if (radeon_connector->edid) {
                         kfree(radeon_connector->edid);
@@ -833,7 +864,8 @@ radeon_dvi_detect(struct drm_connector *connector, bool force)
         bool dret = false;
 
         if (radeon_connector->ddc_bus)
-                dret = radeon_ddc_probe(radeon_connector);
+                dret = radeon_ddc_probe(radeon_connector,
+                                        radeon_connector->requires_extended_probe);
         if (dret) {
                 if (radeon_connector->edid) {
                         kfree(radeon_connector->edid);
@@ -1251,7 +1283,8 @@ radeon_dp_detect(struct drm_connector *connector, bool force)
                                 if (radeon_dp_getdpcd(radeon_connector))
                                         ret = connector_status_connected;
                         } else {
-                                if (radeon_ddc_probe(radeon_connector))
+                                if (radeon_ddc_probe(radeon_connector,
+                                                     radeon_connector->requires_extended_probe))
                                         ret = connector_status_connected;
                         }
                 }
@@ -1406,6 +1439,9 @@ radeon_add_atom_connector(struct drm_device *dev,
         radeon_connector->shared_ddc = shared_ddc;
         radeon_connector->connector_object_id = connector_object_id;
         radeon_connector->hpd = *hpd;
+        radeon_connector->requires_extended_probe =
+                radeon_connector_needs_extended_probe(rdev, supported_device,
+                                                        connector_type);
         radeon_connector->router = *router;
         if (router->ddc_valid || router->cd_valid) {
                 radeon_connector->router_bus = radeon_i2c_lookup(rdev, &router->i2c_info);
@@ -1752,6 +1788,9 @@ radeon_add_legacy_connector(struct drm_device *dev,
         radeon_connector->devices = supported_device;
         radeon_connector->connector_object_id = connector_object_id;
         radeon_connector->hpd = *hpd;
+        radeon_connector->requires_extended_probe =
+                radeon_connector_needs_extended_probe(rdev, supported_device,
+                                                        connector_type);
         switch (connector_type) {
         case DRM_MODE_CONNECTOR_VGA:
                 drm_connector_init(dev, &radeon_connector->base, &radeon_vga_connector_funcs, connector_type);
diff --git a/drivers/gpu/drm/radeon/radeon_display.c b/drivers/gpu/drm/radeon/radeon_display.c
index 28f4655905bc..1a858944e4f3 100644
--- a/drivers/gpu/drm/radeon/radeon_display.c
+++ b/drivers/gpu/drm/radeon/radeon_display.c
@@ -751,8 +751,17 @@ static int radeon_ddc_dump(struct drm_connector *connector)
         if (!radeon_connector->ddc_bus)
                 return -1;
         edid = drm_get_edid(connector, &radeon_connector->ddc_bus->adapter);
+        /* Log EDID retrieval status here. In particular with regard to
+         * connectors with requires_extended_probe flag set, that will prevent
+         * function radeon_dvi_detect() to fetch EDID on this connector,
+         * as long as there is no valid EDID header found */
         if (edid) {
+                DRM_INFO("Radeon display connector %s: Found valid EDID",
+                                drm_get_connector_name(connector));
                 kfree(edid);
+        } else {
+                DRM_INFO("Radeon display connector %s: No monitor connected or invalid EDID",
+                                drm_get_connector_name(connector));
         }
         return ret;
 }
diff --git a/drivers/gpu/drm/radeon/radeon_i2c.c b/drivers/gpu/drm/radeon/radeon_i2c.c
index 781196db792f..6c111c1fa3f9 100644
--- a/drivers/gpu/drm/radeon/radeon_i2c.c
+++ b/drivers/gpu/drm/radeon/radeon_i2c.c
@@ -32,17 +32,17 @@
  * radeon_ddc_probe
  *
  */
-bool radeon_ddc_probe(struct radeon_connector *radeon_connector)
+bool radeon_ddc_probe(struct radeon_connector *radeon_connector, bool requires_extended_probe)
 {
-        u8 out_buf[] = { 0x0, 0x0};
-        u8 buf[2];
+        u8 out = 0x0;
+        u8 buf[8];
         int ret;
         struct i2c_msg msgs[] = {
                 {
                         .addr = 0x50,
                         .flags = 0,
                         .len = 1,
-                        .buf = out_buf,
+                        .buf = &out,
                 },
                 {
                         .addr = 0x50,
@@ -52,15 +52,31 @@ bool radeon_ddc_probe(struct radeon_connector *radeon_connector)
                 }
         };
 
+        /* Read 8 bytes from i2c for extended probe of EDID header */
+        if (requires_extended_probe)
+                msgs[1].len = 8;
+
         /* on hw with routers, select right port */
         if (radeon_connector->router.ddc_valid)
                 radeon_router_select_ddc_port(radeon_connector);
 
         ret = i2c_transfer(&radeon_connector->ddc_bus->adapter, msgs, 2);
-        if (ret == 2)
-                return true;
-
-        return false;
+        if (ret != 2)
+                /* Couldn't find an accessible DDC on this connector */
+                return false;
+        if (requires_extended_probe) {
+                /* Probe also for valid EDID header
+                 * EDID header starts with:
+                 * 0x00,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0x00.
+                 * Only the first 6 bytes must be valid as
+                 * drm_edid_block_valid() can fix the last 2 bytes */
+                if (drm_edid_header_is_valid(buf) < 6) {
+                        /* Couldn't find an accessible EDID on this
+                         * connector */
+                        return false;
+                }
+        }
+        return true;
 }
 
 /* bit banging i2c */
diff --git a/drivers/gpu/drm/radeon/radeon_mode.h b/drivers/gpu/drm/radeon/radeon_mode.h
index 6df4e3cec0c2..d09031c03e26 100644
--- a/drivers/gpu/drm/radeon/radeon_mode.h
+++ b/drivers/gpu/drm/radeon/radeon_mode.h
@@ -438,6 +438,9 @@ struct radeon_connector {
         struct radeon_i2c_chan *ddc_bus;
         /* some systems have an hdmi and vga port with a shared ddc line */
         bool shared_ddc;
+        /* for some Radeon chip families we apply an additional EDID header
+           check as part of the DDC probe */
+        bool requires_extended_probe;
         bool use_digital;
         /* we need to mind the EDID between detect
            and get modes due to analog/digital/tvencoder */
@@ -514,7 +517,8 @@ extern void radeon_i2c_put_byte(struct radeon_i2c_chan *i2c,
                                 u8 val);
 extern void radeon_router_select_ddc_port(struct radeon_connector *radeon_connector);
 extern void radeon_router_select_cd_port(struct radeon_connector *radeon_connector);
-extern bool radeon_ddc_probe(struct radeon_connector *radeon_connector);
+extern bool radeon_ddc_probe(struct radeon_connector *radeon_connector,
+                        bool requires_extended_probe);
 extern int radeon_ddc_get_modes(struct radeon_connector *radeon_connector);
 
 extern struct drm_encoder *radeon_best_encoder(struct drm_connector *connector);