[Bug 105325] [KBL LSPCON] Linux will reboot when installing with connect HDMI monitor (include PS175 LSPCON)

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=105325

Sam <saml at supermicro.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |AnW at supermicro.com,
                   |                            |saml at supermicro.com

--- Comment #9 from Sam <saml at supermicro.com> ---
Hi Elizabeth,

I found something looks not usual in the log. Check those below:


============================================================================
 三  05 09:31:11 supermicro-X11SSN-E kernel: [drm:drm_dp_dual_mode_detect
[drm_kms_helper]] DP dual mode HDMI ID:  (err -6)
 三  05 09:31:11 supermicro-X11SSN-E kernel: [drm:drm_helper_hpd_irq_event
[drm_kms_helper]] [CONNECTOR:63:HDMI-A-1] status updated from unknown to
disconnected
============================================================================

DP dual mode HDMI ID: err -6 and I checked the error code in the kernel and -6
means /* No such device or address */

I tried to find the root cause and found the following logs 

=============================================================================
 三  05 09:31:11 supermicro-X11SSN-E kernel: [drm:gmbus_xfer [i915]] GMBUS [i915
gmbus dpc] /ENX for addr: 0050 w(1)
 三  05 09:31:11 supermicro-X11SSN-E kernel: [drm:gmbus_xfer [i915]] GMBUS [i915
gmbus dpc] NAK on first message, retry
 三  05 09:31:11 supermicro-X11SSN-E kernel: [drm:gmbus_xfer [i915]] GMBUS [i915
gmbus dpc] NAK for addr: 0050 w(1)
 三  05 09:31:11 supermicro-X11SSN-E kernel: [drm:drm_do_probe_ddc_edid [drm]]
drm: skipping non-existent adapter i915 gmbus dpc
 三  05 09:31:11 supermicro-X11SSN-E kernel: [drm:gmbus_xfer [i915]] GMBUS [i915
gmbus dpc] NAK for addr: 0040 w(1)
 三  05 09:31:11 supermicro-X11SSN-E kernel: [drm:gmbus_xfer [i915]] GMBUS [i915
gmbus dpc] NAK on first message, retry
============================================================================

It seems like the system keeps probing the addr 0050 and 0040 but failed to get
ack ( NAK received ) which causes the failure of HDMI connection in the end.

I am not sure why system failed to get ack. Please let me know if you may have
any thinking.


Thanks



Sam

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