Den 11.03.2019 20.29, skrev Daniel Vetter:
> On Mon, Mar 11, 2019 at 08:23:38PM +0100, Daniel Vetter wrote:
>> On Mon, Mar 11, 2019 at 06:42:16PM +0100, Noralf Trønnes wrote:
>>> This adds support for outputting kernel messages on panic().
>>> A kernel message dumper is used to dump the log. The dumper iterates
>>> over each DRM device and it's crtc's to find suitable framebuffers.
>>>
>>> All the other dumpers are run before this one except mtdoops.
>>> Only atomic drivers are supported.
>>>
>>> Signed-off-by: Noralf Trønnes <noralf@xxxxxxxxxxx>
<snip>
>>> +static void drm_panic_try_dev(struct drm_device *dev, struct kmsg_dumper *dumper)
>>> +{
>>> + struct drm_framebuffer *fb;
>>> + struct drm_plane *plane;
>>> + struct drm_crtc *crtc;
>>> +
>>> + if (!drm_core_check_feature(dev, DRIVER_ATOMIC))
>>> + return;
>>> +
>>> + if (dumper->max_reason == KMSG_DUMP_OOPS)
>>> + pr_info("%s: %s on minor %d\n", __func__, dev->driver->name,
>>> + dev->primary->index);
>>> +
>>> + drm_for_each_crtc(crtc, dev) {
>>> + if (!ww_mutex_trylock(&crtc->mutex.mutex))
>>> + continue;
>>> +
>>> + if (!crtc->enabled || !crtc->primary)
>>> + goto crtc_unlock;
>>> +
>>> + if (!crtc->state || !crtc->state->active)
>>> + goto crtc_unlock;
>>> +
>>> + plane = crtc->primary;
>>> + if (!ww_mutex_trylock(&plane->mutex.mutex))
>>> + goto crtc_unlock;
>>> +
>>> + /*
>>> + * TODO: Should we check plane_state->visible?
>>> + * It is not set on vc4
>>
>> I think we should. We should also check whether that primary is connected
>> to the crtc (some hw you can reassign planes freely between crtc, and the
>> crtc->primary pointer is only used for compat with legacy ioctl).
>>
>>> + if (!plane->state || !plane->state->visible)
>>> + */
>>> + if (!plane->state)
>>> + goto plane_unlock;
>>> +
>>> + fb = plane->state->fb;
>>> + if (!fb || !fb->funcs->panic_vmap)
>>
>> Docs says this is optional, doesn't seem to be all that optional. I'd
>> check for this or a driver-specific ->panic_draw_xy instead.
>>> + goto plane_unlock;
>>> +
>>> + /*
>>> + * fbcon puts out panic messages so stay away to avoid jumbled
>>> + * output. If vc->vc_mode != KD_TEXT fbcon won't put out
>>> + * messages (see vt_console_print).
>>> + */
>>> + if (dev->fb_helper && dev->fb_helper->fb == fb)
>
> This is a bit a layering violation. Could we instead tell fbcon that it
> shouldn't do panic handling for drm drivers? I think that would resolve
> this overlap here in a much cleaner way. drm fbdev helpers already have
> lots of oops_in_progress checks all over to make sure fbcon doesn't do
> anything bad. That only leaves the actual rendering, which I think we can
> stop too with a simple flag.
>
> Ofc only for atomic drivers which have this panic handling mode here
> implemented.
There used to be a fbdev flag FBINFO_CAN_FORCE_OUTPUT that controlled
vc->vc_panic_force_write, but it's gone now I see.
Noralf.
> -Daniel
>
>>> + goto plane_unlock;
>>> +
>>> + drm_panic_kmsg_render_screen(plane, dumper);
>>> +plane_unlock:
>>> + ww_mutex_unlock(&plane->mutex.mutex);
>>> +crtc_unlock:
>>> + ww_mutex_unlock(&crtc->mutex.mutex);
>>> + }
>>> +}
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