Re: [Intel-gfx] drm_kms_helper problems

From: Mark Hounschell
Date: Sun Oct 21 2012 - 14:18:36 EST

Hi Bruno,

On 10/21/2012 10:58 AM, Bruno PrÃmont wrote:
Hi mark,

On Sun, 21 October 2012 Mark Hounschell <dmarkh@xxxxxxxxxx> wrote:
I have a TV that appears to not provide proper EDID info to the HDMI or DVI
ports of my Intel DH77DF motherboard. I received some pointers from this
list that pointed me in the direction of creating my own EDID file and I
now have a binary blob that matches what the service manual says is the
proper EDID info.

But I am unable to get the drm_kms_helper module to load and use this file.
My relevant kernel config options are.


my relevant kernel command line contains:


The variant without card0- should be the right one.

OK. Changed it. What if I had more than one video card?

The edid file:
# ls -al /lib/firmware/edid/lg42lb9df_hdmi1.edid
-rw-r--r-- 1 root root 256 Oct 16 05:46 /lib/firmware/edid/lg42lb9df_hdmi1.edid

connector info from /sys/class/drm/

card0 card0-DP-1 card0-DP-2 card0-DP-3 card0-HDMI-A-1 card0-HDMI-A-2
card0-HDMI-A-3 card0-VGA-1 controlD64 version

Which should I use? HDMI-A-1, HDMI-A-2, or HDMI-A-3? Why re there 3??

And I don't really understand why I have 3 entries for the one hdmi port?
Nor do I really understand _exactly_ how to define the connector in my
kernel command line or which of the 3 connectors from /sys I should be
using. I've tried different variants. Ie. card0-HDMI-A-1and HDMI-A-1.

The results in the kernel log file remain:

[ 1.879654] drm_kms_helper: Unknown parameter `edid'

As your drm_kms_helper is built modular, did you try not putting that
parameter on kernel cmdline but rather put it in modprobe's configuration
for that module? (may doing the whole loading manually).

I've created a /etc/modprobe.d/20-drm_kms_helper.conf with:
options drm_kms_helper edid_firmware=HDMI-A-1:edid/lg42lb9df_hdmi1.edid
and now I'm getting something different. It looks like it's trying. In fact I actually get a screen on the TV now. It's not 1920x1080 but 1024x768 at 60hz.

[ 1.883124] load_module: Calling parse_args for module = drm_kms_helper args = edid_firmware=HDMI-A-1:edid/lg42lb9df_hdmi1.edid
[ 1.883126]
[ 1.883126] parse_args: (1) Entered for drm_kms_helper
[ 1.883127]
[ 1.883127] parse_args: (2) Entered for drm_kms_helper
[ 1.883127] parse_args: doing = drm_kms_helper
[ 1.883128] parse_args: args = edid_firmware=HDMI-A-1:edid/lg42lb9df_hdmi1.edid
[ 1.883129] parse_args: num = 2
[ 1.883130] parse_args: min_level = -32768
[ 1.883131] parse_args: max_level = 32767
[ 1.883132]
F\xffffffc9\xfffffff8h\xffffff89\xffffff86\xffffffc0\xffffff80\xffffffff\xffffffff\xffffffd4R\xffffffc9\xfffffff8TF\xffffffc9\xfffffff88\xffffff89\xffffff86\xffffffc0\xffffffa4\xffffffff\xffffffffdF\xffffffc9\xfffffff8, num=2, min_level=-32768, max_level=32767
[ 1.886855]
[ 2.132749] [drm] forcing HDMI-A-1 connector ON
[ 2.132752] [drm] forcing HDMI-A-2 connector ON
[ 2.132753] [drm] forcing HDMI-A-3 connector ON

[ 2.189769] [drm:edid_load] *ERROR* Requesting EDID firmware "edid/lg42lb9df_hdmi1.edid" failed (err=-2)

I get a couple of the above messages.

[ 2.388623] [drm:drm_edid_block_valid] *ERROR* EDID checksum is invalid, remainder is 130
[ 2.388631] Raw EDID:
[ 2.388635] 00 ff ff ff ff ff ff 00 ff ff ff ff ff ff ff ff

# modprobe drm_kms_helper edid_firmware=HDMI-A-1:edid/lg42lb9df_hdmi1.edid

I can't seem to rm the modules already loaded to try this.

I have no idea why it fails for you, here on the systems I have it works
fine (on one where everything is built into the kernel I did set the cmdline
arguments via CONFIG_CMDLINE="..." (having CONFIG_CMDLINE_BOOL=y).

I assume I am doing something wrong but I have put some debug printks in
kernel/params.c that shows me every call made to it and it's params. It is
entered many times and I see a sequence to in the log file. As an example,
the last one to call with params before drm_kms_helper is "late" and here
are my debug prints for it:

Did you check that your bootloader get things right, e.g. if results are the
same no matter in which order you put the kernel parameters (and if there are
some non-ASCII values in there).
As you have quite some length of parameters there could be some buffer size
(take this as just wild guessing)

The bootloader file is clean. Want me to send a complete dmesg again?


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