Re: [PATCH v2] drm/loongson: stop to set get_vblank_timestamp for LS7A1000 CRTC

[Thomas Zimmermann]

Hi

Am 23.03.26 um 12:42 schrieb Icenowy Zheng:
[...]
> > > drm_update_vblank_count+0xac/0x418
> > > [    0.334960] [<ffffffff80be6270>] drm_vblank_enable+0xf0/0x288
> > > [    0.334960] [<ffffffff80be7010>] drm_vblank_get+0xf8/0x160
> > > [    0.334960] [<ffffffff80beb2e0>]
> > > drm_client_modeset_wait_for_vblank+0x50/0xa0
> I doubt the problem here is that the function above is called with
> hardcoded 0 by drm_fb_helper_fb_dirty() (being inlined into
> drm_fb_helper_damage_work() by the compiler). Then on my setup it
> failed because my primary output (laptop LCD) is on CRTC 1 (CRTC 0 is
> external HDMI instead).

The CRTC 0 has vblank interrupt. The CRTC 1 does not. Is that correct?

> This is new behavior introduced by d8c4bddcd8bc ("drm/fb-helper:
> Synchronize dirty worker with vblank"), and the commit messages say
> `This allows several screen updates to pile up and acts as a rate
> limiter.` .

This should work if the vblanks are configured correctly.


> Should it wait for any vblanks instead of waiting for one on CRTC 0 ?
> (Or check whether CRTC 0 is on before waiting on it?)

It should only wait for the vblank on the CRTC it uses (1 in your case).

Best regards
Thomas


> Thanks,
> Icenowy
>
> > > [    0.334960] [<ffffffff80c0a144>]
> > > drm_fb_helper_damage_work+0x8c/0x1d8
> > > [    0.334960] [<ffffffff8028fac8>] process_one_work+0x198/0x348
> > > [    0.334960] [<ffffffff802906c0>] worker_thread+0x238/0x390
> > > [    0.334960] [<ffffffff8029c0d8>] kthread+0x160/0x198
> > > [    0.334960] [<ffffffff8021fd8c>]
> > > ret_from_kernel_thread+0x14/0x1c
> > >
> > > [    0.334960] ---[ end trace 0000000000000000 ]---
> > > ```
> > >
> > > > > > Signed-off-by: Icenowy Zheng <zhengxingda@xxxxxxxxxxx>
> > > > > Oh forgot to attach when crafting v2:
> > > > >
> > > > > ```
> > > > > Acked-by: Thomas Zimmermann <tzimmermann@xxxxxxx>
> > > > > ```
> > > > >
> > > > > > ---
> > > > > > Changes in v2:
> > > > > > - Re-formatted Loongson product model numbers per request
> > > > > > from
> > > > > > Huacai.
> > > > > >
> > > > > >     drivers/gpu/drm/loongson/lsdc_crtc.c | 1 -
> > > > > >     1 file changed, 1 deletion(-)
> > > > > >
> > > > > > diff --git a/drivers/gpu/drm/loongson/lsdc_crtc.c
> > > > > > b/drivers/gpu/drm/loongson/lsdc_crtc.c
> > > > > > index 587fbe285e9ef..b3af8e0cdb15f 100644
> > > > > > --- a/drivers/gpu/drm/loongson/lsdc_crtc.c
> > > > > > +++ b/drivers/gpu/drm/loongson/lsdc_crtc.c
> > > > > > @@ -721,7 +721,6 @@ static const struct drm_crtc_funcs
> > > > > > ls7a1000_crtc_funcs = {
> > > > > >     	.late_register = lsdc_crtc_late_register,
> > > > > >     	.enable_vblank = lsdc_crtc_enable_vblank,
> > > > > >     	.disable_vblank = lsdc_crtc_disable_vblank,
> > > > > > -	.get_vblank_timestamp =
> > > > > > drm_crtc_vblank_helper_get_vblank_timestamp,
> > > > > >     	.atomic_print_state = lsdc_crtc_atomic_print_state,
> > > > > >     };
> > > > > >     

--
--
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Frankenstr. 146, 90461 Nürnberg, Germany, www.suse.com
GF: Jochen Jaser, Andrew McDonald, Werner Knoblich, (HRB 36809, AG Nürnberg)