R200 DRM/KMS

[Emil Velikov]

On 8 July 2015 at 14:55, Alex Deucher <alexdeucher at gmail.com> wrote:
> On Wed, Jul 8, 2015 at 9:53 AM, Steven Newbury <steve at snewbury.org.uk> wrote:
>>
>>
>> On Wed Jul 8 14:20:28 2015 GMT+0100, Alex Deucher wrote:
>>> On Wed, Jul 8, 2015 at 8:58 AM, Steven Newbury <steve at snewbury.org.uk> wrote:
>>> >
>>> >
>>> > On Tue Jul 7 15:12:28 2015 GMT+0100, Alex Deucher wrote:
>>> >> On Tue, Jul 7, 2015 at 9:46 AM, Steven Newbury <steve at snewbury.org.uk> wrote:
>>> >> >
>>> >> > I've tried an xserver-1.16, and ddx, libdrm without LTO and with
>>> >> > gcc4.9.  Exactly the same thing.  I wondered whether the unused i810
>>> >> > could be interfering but triggering a device "remove" before starting
>>> >> > X made no difference.
>>> >> >
>>> >> > I'm a bit of a loss.  I suppose I could try writing a simple test for
>>> >> > drmSetInterfaceVersion().  At least that should determine whether the
>>> >> > xserver/ddx is in the clear.
>>> >> >
>>> >> > Any other ideas?
>>> >> >
>>> >>
>>> >> Can you start a non-X runlevel and start X manually as root (assuming
>>> >> you are using a login manager now)?
>>> >>
>>> > My test program worked fine. I considerably improved it over the version I posted. I'll send it to the list when I get back.
>>> >
>>> > I removed the drmSetInterfaceVersion() from radeon_kms.c and it got much further.  Starting Xserver as root  apparently started normally, according to the log, although  there was a permission denied error on mode set during init. I don't know whether it was related or not, but the display then hung with a non-blinking cursor. Strange to get a permission denied as root!
>>> >
>>> > Starting GNOME via gdm gives a working slow X session but for some reason only uses sw dri even though the Xorg log shows r200 DRI2 as initialized. Perhaps it's a config error somewhere.. ?
>>> >
>>> > startx as a regular user just works!
>>> >
>>> > But mutter doesn't, perhaps that's
>>> > why a gnome session isn't working. It just gives the following error:
>>> > Cogl-ERROR **: Failed to create texture 2d due to size/format constraints
>>> >
>>> > Mutter is supposed to work on r200, right?
>>>
>>> IIRC it tries to use a render buffer format that's not supported by the hw.
>> Is there anything to be done about it? Have to use a different wm/compositor?
>>
>
> Another wm or compositor may help.
>
>> Any idea why removing the call from radeon_kms.c worked?
>
> No idea.
>
>From a quick look at the actual implementation drmSetInterfaceVersion
is not something that we want/need to use with KMS drivers.

In general the original issue sound like the drm driver is not (fully)
loaded before the xserver/ddx kicks in. Additionally it may be a race
condition if something else (plymouth) is using the device. In the
latter case DRM_MASTER might still be held by $(other_app), thus
attempting to either SetInterfaceVersion or do any modeset operation
will fail.

Personally I would add a healthy amount of printk/printf though the
kernel drm + radeon and the ddx.

Cheers
Emil