[Bug 65757] [snb pch eDP regression] Screen sometimes remains black after mode change - old fast & narrow link is more stable

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=65757

Egbert Eich <eich at pdx.freedesktop.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|ASSIGNED                    |RESOLVED
         Resolution|---                         |NOTOURBUG

--- Comment #10 from Egbert Eich <eich at pdx.freedesktop.org> ---
Meanwhile Chrontel has updated the firmware for their (e)DP -> LVDS converter.

The new firmware does not exhibit the issue any more.
Here is the explanation given by Chrontel regarding the cause of the issue and
the change made to the firmware:

Here the information about root cause and countermeasure by Chrontel IC f/w
from Chrontel vendor.
============================================================
Root cause:
Chrontel IC CH7511B communicate with OS by DP AUX command for LCD signal
control.
DP Tx drivers seems to be different between SLE11SP2 and SLE11SP3,
and different DP Tx drivers send a bit different command sequences to DP Rx and
set a bit different of timeout of DP AUX command response between SLE11SP2 and
SLE11SP3.
The timeout of DP AUX command response happen occasionally in SLE11SP3 and it
cause black screen in SLE11SP3.

Countermeasure by Chrontel IC f/w:
With MCU embedded in Chrontel IC CH7511B, the issue can be fixed by revising
the firmware of MCU.
Change the interrupt mode and fine-tune the DPCD registers access code, so as
to rapidly respond the DP Tx AUX commands.
AUX responds time of previous firmware  ->around 280us
AUX responds time of new firmware for countermeasure of SP3 issue ->around
250us
Chrontel vendor also tested working well by the new f/w on heave traffic
condition (it means the worse case).
==============================================================
The description of the cause does not match the observations made while
investigating this bug.
However since the symptoms of the issue are gone with the latest Chrontel
firmware and we don't get more support by either the manufacturer of the system
or Chrontel we will close this ticket with NOTOURBUG.

-- 
You are receiving this mail because:
You are the QA Contact for the bug.
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.freedesktop.org/archives/intel-gfx-bugs/attachments/20130715/36afb245/attachment.html>