1 files changed, 24 insertions, 8 deletions

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 */