linux-kernel - Re: [Intel-gfx] drm_kms

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Date:	Sun, 21 Oct 2012 16:58:02 +0200
From:	Bruno Prémont <bonbons@...ux-vserver.org>
To:	dmarkh@....rr.com
Cc:	linux-kernel@...r.kernel.org,
	"markh@...pro.net >> Mark Hounschell" <markh@...pro.net>,
	Intel Graphics Development <intel-gfx@...ts.freedesktop.org>
Subject: Re: [Intel-gfx] drm_kms_helper problems

Hi mark,

On Sun, 21 October 2012 Mark Hounschell <dmarkh@....rr.com> 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.
> 
> CONFIG_DRM_KMS_HELPER=m
> CONFIG_DRM_LOAD_EDID_FIRMWARE=y
> 
> my relevant kernel command line contains:
> 
> video=card0-HDMI-A-1:e 
> drm_kms_helper.edid_firmware=card0-HDMI-A-1:edid/lg42lb9df_hdmi1.edid

The variant without card0- should be the right one.

> 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
> 
> 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).

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

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
issue.
(take this as just wild guessing)

Bruno


> [    0.840206] parse_args: Entered for late
> [    0.840207] parse_args: doing = late
> [    0.840208] parse_args: args  = 
> root=/dev/disk/by-id/ata-INTEL_SSDSC2CW060A3_CVCV205106EB060AGN-part4 
> video=1024x768 
> resume=/dev/disk/by-id/ata-INTEL_SSDSC2CW060A3_CVCV205106EB060AGN-part3 
> splash=silent quiet vga=0x37e irqpoll video=card0-HDMI-A-1:e 
> drm_kms_helper.edid_firmware=card0-HDMI-A-1:edid/lg42lb9df_hdmi1.edid
> [    0.840209] parse_args: params =
> [    0.840210] parse_args: num = 174
> [    0.840210] parse_args: min_level = 7
> [    0.840211] parse_args: max_level = 7
> 
> Now when it gets to drm_kms_helper this is what I get and this is certainly 
> screwed up, I just don't know why.
> 
> [    1.879648] parse_args: Entered for drm_kms_helper
> [    1.879648] parse_args: doing = drm_kms_helper
> [    1.879649] parse_args: args  = edid
> \xffffff86\xffffffe2\xfffffff8h\xffffff89\xffffff86\xffffffc0\xffffff80\xffffffff\xffffffffԒ\xffffffe2\xfffffff8T\xffffff86\xffffffe2\xfffffff88\xffffff89\xffffff86\xffffffc0\xffffffa4\xffffffff\xffffffffd\xffffff86\xffffffe2\xfffffff8
> [    1.879650] parse_args: num = 2
> [    1.879651] parse_args: min_level = -32768
> [    1.879651] parse_args: max_level = 32767
> [    1.879653]
> \xffffff86\xffffffe2\xfffffff8h\xffffff89\xffffff86\xffffffc0\xffffff80\xffffffff\xffffffffԒ\xffffffe2\xfffffff8T\xffffff86\xffffffe2\xfffffff88\xffffff89\xffffff86\xffffffc0\xffffffa4\xffffffff\xffffffffd\xffffff86\xffffffe2\xfffffff8, 
> num=2, min_level=-32768, max_level=32767
> 
> Then finally:
> 
> [    1.879654] drm_kms_helper: Unknown parameter `edid'
> 
> The additional printks I inserted into kernel/params.c:
> 
>          if (*args)
>                  pr_debug("doing %s, parsing ARGS: '%s'\n", doing, args);
> 
> +      if (*args) {
> +              printk("\nparse_args: Entered for %s\n", doing);
> +              printk("parse_args: doing = %s\n", doing);
> +              printk("parse_args: args  = %s\n", args);
> +              printk("parse_args: params = %s\n", params);
> +              printk("parse_args: num = %d\n", num);
> +              printk("parse_args: min_level = %d\n",min_level);
> +              printk("parse_args: max_level = %d\n", max_level);
> +       }
> 
>          while (*args) {
> 
> This is using a vanilla 3.6.2 kernel. Any help would be appreciated.
> 
> Regards
> Mark
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