On Mon, May 04, 2020 at 02:07:22PM +0200, Thomas Zimmermann wrote: > Hi Emil > > Am 01.05.20 um 15:20 schrieb Emil Velikov: > > Hi Thomas, > > > > Couple of fly-by ideas/suggestions. > > > > On Thu, 30 Apr 2020 at 10:13, Thomas Zimmermann <tzimmermann@xxxxxxx> wrote: > >> > >> Suspending failed because there's no mode if the CRTC is being > >> disabled. Early-out in this case. This fixes runtime PM for ast. > >> > >> Signed-off-by: Thomas Zimmermann <tzimmermann@xxxxxxx> > >> --- > >> drivers/gpu/drm/ast/ast_mode.c | 3 +++ > >> 1 file changed, 3 insertions(+) > >> > >> diff --git a/drivers/gpu/drm/ast/ast_mode.c b/drivers/gpu/drm/ast/ast_mode.c > >> index 7a9f20a2fd303..089b7d9a0cf3f 100644 > >> --- a/drivers/gpu/drm/ast/ast_mode.c > >> +++ b/drivers/gpu/drm/ast/ast_mode.c > >> @@ -801,6 +801,9 @@ static int ast_crtc_helper_atomic_check(struct drm_crtc *crtc, > >> return -EINVAL; > > Unrelated: > > This feels quite dirty. If AST1180 does not support atomic modeset > > simply remove the DRIVER_ATOMIC bit. > > You can do that at runtime, via drm_device::driver_features in say, > > ast_detect_chip()? > > The line you commented on dates back to non-atomic modesetting, but I > don't know what the story behind AST1180 is. It is explicitly disabled > in the list of PCI IDs, but the driver has plenty of code for it. It > looks as if the chip can only do pageflipping with a pre-set video mode. > > As it is right now, the AST1180 code could probably be deleted entirely. > > > > > The drm_driver::driver_features is immutable, or it ought to be. > > > >> } > >> > >> + if (!state->enable) > >> + return 0; /* no checks required if CRTC is being disabled */ > >> + > > I cannot think of a reason why a driver would need to perform > > crtc_atomic_check, if the crtc is being disabled. > > Can you spot any? If not, this should be better served in core, which > > calls this callback. > > Correct? > Ast is a bit of a special case, because it tests the incoming mode > against a list of re-defined modes. With the crtc being disabled, the > incoming mode is 0 in all fields. Obviously that's not a valid mode, and > we need that additional test here. > > In the general case, I'd see 'crtc check' as part of the larger atomic > infrastructure. I can imagine that configurations require the CRTC to be > enabled before other HW blocks work. So a driver might have a reason to > run crtc's check even for disabled crtcs (at least to verify that the > crtc is not disabled). I don't think this can be handled in the core easily. Jumping out of ->atomic_check callbacks when stuff is all off is fairly standard pattern. So much standard that I'm kinda wondering whether we shouldn't just make it the default in atomic helpers - so many drivers forget to do it and break in funny ways. -Daniel > > Best regards > Thomas > > > > > HTH > > -Emil > > _______________________________________________ > > dri-devel mailing list > > dri-devel@xxxxxxxxxxxxxxxxxxxxx > > https://lists.freedesktop.org/mailman/listinfo/dri-devel > > > > -- > Thomas Zimmermann > Graphics Driver Developer > SUSE Software Solutions Germany GmbH > Maxfeldstr. 5, 90409 Nürnberg, Germany > (HRB 36809, AG Nürnberg) > Geschäftsführer: Felix Imendörffer > > _______________________________________________ > dri-devel mailing list > dri-devel@xxxxxxxxxxxxxxxxxxxxx > https://lists.freedesktop.org/mailman/listinfo/dri-devel -- Daniel Vetter Software Engineer, Intel Corporation http://blog.ffwll.ch _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/dri-devel
