[Openchrome-devel] [Bug 65591] New: [drm-openchrome] Commit 484c66c400daa76bd6840f195e8effa9d39dfb3c breaks KMS on VX900 with HDMI

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=65591

          Priority: medium
            Bug ID: 65591
          Assignee: openchrome-devel at lists.freedesktop.org
           Summary: [drm-openchrome] Commit
                    484c66c400daa76bd6840f195e8effa9d39dfb3c breaks KMS on
                    VX900 with HDMI
          Severity: major
    Classification: Unclassified
                OS: All
          Reporter: bugs.freedesktop.org at hardfalcon.net
          Hardware: All
            Status: NEW
           Version: git
         Component: Driver/openchrome
           Product: xorg

With commit 484c66c400daa76bd6840f195e8effa9d39dfb3c, the following change
(among others) was introduced in the file drivers/gpu/drm/via/via_hdmi.c:

@@ -432,8 +433,8 @@ via_ddc_read_bytes_by_hdmi(struct drm_via_private
*dev_priv, unsigned char *bloc
     if (status)
         status = via_check_hdmi_i2c_status(dev_priv, 0x0008, true);
-    /* Offset - always read at start of buffer */
-    temp = 0;
+    /* Offset */
+    temp = offset;
     temp <<= 16;
     temp |= VIA_READ(0xC0B4) & 0xFF00FFFF;
     VIA_WRITE(0xC0B4, temp);



This breaks KMS on my VX900, the (1920x1080 HDMI) display goes blank/into
standby mode immediately after the module was loaded (from initrd). Changing
the line
temp = offset;
back to
temp = 0;
fixes the problem (but of course this renders the offset parameter of the
function useless).

My guess is that line 525 in the same file needs to be changed from
offset = (valid_extensions + 1) * EDID_LENGTH;
to
offset = (valid_extensions) * EDID_LENGTH;

I haven't tested this, though.

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