[PATCH v6 1/4] drm/layerscape: Add Freescale DCU DRM driver

Daniel Vetter
2015-07-10T16:59:49Z

On Fri, Jul 10, 2015 at 10:43:11AM +0000, Wang J.W. wrote:
> Hi Daniel,
>
> Thank you very much for your review!
> See below...
>
> > -----Original Message-----
> > From: Daniel Vetter [mailto:daniel.vetter at ffwll.ch] On Behalf Of Daniel
> > Vetter
> > Sent: Friday, July 10, 2015 4:00 PM
> > To: Wang Jianwei-B52261
> > Cc: dri-devel at lists.freedesktop.org; linux-kernel at vger.kernel.org; linux-
> > arm-kernel at lists.infradead.org; devicetree at vger.kernel.org;
> > airlied at linux.ie; daniel.vetter at ffwll.ch; mark.yao at rock-chips.com; Wood
> > Scott-B07421; Wang Huan-B18965; Xiubo Li
> > Subject: Re: [PATCH v6 1/4] drm/layerscape: Add Freescale DCU DRM driver
> >
> > On Fri, Jul 10, 2015 at 03:26:52PM +0800, Jianwei Wang wrote:
> > > + .atomic_check = fsl_dcu_drm_encoder_atomic_check,
> >
> > .atomic_check is optional
> >
>
> I try to remove .atomic_check, but it will cause CPU hang when starting up
> And I find this in drivers/gpu/drm/drm_atomic_helper.c
>
> 293 if (funcs->atomic_check) {
> 294 ret = funcs->atomic_check(encoder, crtc_state,
> 295 conn_state);
> 296 if (ret) {
> 297 DRM_DEBUG_ATOMIC("[ENCODER:%d:%s] check failed\n",
> 298 encoder->base.id, encoder->name);
> 299 return ret;
> 300 }
> 301 } else {
> 302 ret = funcs->mode_fixup(encoder, &crtc_state->mode,
> 303 &crtc_state->adjusted_mode);
> 304 if (!ret) {
> 305 DRM_DEBUG_ATOMIC("[ENCODER:%d:%s] fixup failed\n",
> 306 encoder->base.id, encoder->name);
> 307 return -EINVAL;
> 308 }
> 309 }
> It means that I have to implement at least one of atomic_check and mode_fixup.
> So I reserve atomic_check.
> Is there problem? Please give me some more comments if necessary. Thanks!

Ah sorry you are right, atomic check is not optional. Unfortunately the
optional-or-not thing has grown a bit organically so there's no clear
rules.
-Daniel
--
Daniel Vetter
Software Engineer, Intel Corporation