[Intel-gfx] [PATCH] drm/i915: Delete the strict EDID check for SDVO DVI-D monitor

[Dave Airlie]

On Thu, Oct 22, 2009 at 7:41 PM, ykzhao <yakui.zhao at intel.com> wrote:
> On Thu, 2009-10-22 at 15:15 +0800, Keith Packard wrote:
>> Excerpts from yakui.zhao's message of Thu Oct 22 14:25:33 +0900 2009:
>> > From: Zhao Yakui <yakui.zhao at intel.com>
>> >
>> > In theory we can use EDID obtained from the DVI-D monitor to detect whether
>> > the device is connected or not.
>>
>> The DVI spec *requires* EDID on DVI-D monitors. Do we have any
>> information on why this is failing? Perhaps our EDID code is broken
>> for some monitors?
> This issue happens on one SDVO card with multiple inputs and multiple
> outputs.
>
> At first IMO maybe this is related with the incorrect DDC bus behind
> SDVO card. I write a debug patch which tries to read 128byte by using
> different DDC bus.(PROM, DDC1, DDC2, DDC3).
> Unfortunately it can read nothing even when the different DDC bus is
> used. It always reports that there doesn't exist the 0xA0 slave address.
>
> But one bug reporter can read the EDID by using the
> read-edid-tool(1.4.2), which is realized by using BIOS call.
>
> It is very interesting. Maybe our I2C bus code is different with that
> used in Video-BIOS.
>

You should be able to at least figure out which DDC lines the BIOS
is using to narrow down whether its incorrect timing, incorrect DDC
or some SDVO bus interaction issue. None of these are something
the initial patch fixes.

Dave.