On Thu, Mar 21, 2019 at 04:27:06PM +0100, Paul Kocialkowski wrote: > Hi, > > Le mercredi 20 mars 2019 à 09:56 -0700, Eric Anholt a écrit : > > Paul Kocialkowski <paul.kocialkow...@bootlin.com> writes: > > > > > The firstopen DRM driver hook was initially used to perform hardware > > > initialization, which is now considered legacy. Only a single user of > > > firstopen remains at this point (savage). > > > > > > In some specific cases, non-legacy drivers may also need to implement > > > these hooks. For instance on VC4, we need to allocate a 16 MiB buffer > > > for the GPU. Because it's not required for fbcon, it's a waste to > > > allocate it before userspace starts using the DRM device. > > > > > > Using firstopen and lastclose for this allocation seems like the best > > > fit, so re-habilitate the hook to allow it to be called for non-legacy > > > drivers. > > > > > > Signed-off-by: Paul Kocialkowski <paul.kocialkow...@bootlin.com> > > > --- > > > drivers/gpu/drm/drm_file.c | 3 +-- > > > include/drm/drm_drv.h | 2 +- > > > 2 files changed, 2 insertions(+), 3 deletions(-) > > > > > > diff --git a/drivers/gpu/drm/drm_file.c b/drivers/gpu/drm/drm_file.c > > > index b1838a41ad43..c011b5cbfb6b 100644 > > > --- a/drivers/gpu/drm/drm_file.c > > > +++ b/drivers/gpu/drm/drm_file.c > > > @@ -266,8 +266,7 @@ static int drm_setup(struct drm_device * dev) > > > { > > > int ret; > > > > > > - if (dev->driver->firstopen && > > > - drm_core_check_feature(dev, DRIVER_LEGACY)) { > > > + if (dev->driver->firstopen) { > > > ret = dev->driver->firstopen(dev); > > > if (ret != 0) > > > return ret; > > > diff --git a/include/drm/drm_drv.h b/include/drm/drm_drv.h > > > index ca46a45a9cce..aa14607e54d4 100644 > > > --- a/include/drm/drm_drv.h > > > +++ b/include/drm/drm_drv.h > > > @@ -236,7 +236,7 @@ struct drm_driver { > > > * to set/unset the VT into raw mode. > > > * > > > * Legacy drivers initialize the hardware in the @firstopen callback, > > > - * which isn't even called for modern drivers. > > > + * modern drivers can use it for other purposes only. > > > */ > > > void (*lastclose) (struct drm_device *); > > > > Our usage in vc4 is not very different from what we called "hardware > > initialization" in other devices. I would rather just delete this > > sentence entirely. > > Sounds good to me! > > > The only alternative I can think of to using a firstopen/lastclose-style > > allocation for this would be to allocate the bin bo on the first > > (non-dumb?) V3D BO allocation and refcount those to free the binner. > > I don't see other options either, and using firstclose/lastopen feels > overall more readable in the driver code. > > I'm not sure there is such a big overhead associated with allocating > the binner BO (it seems that the current implementation tries to alloc > until the specific memory constraints for the buffer are met, so > perhaps that can take time). But if there is, I suppose it's best to > have that when starting up rather than delaying the first render > operation.
I'm not entirely buying the "we don't need this for fbcon only" argument - there's plenty of dumb kms clients too (boot splash and whatever else there might be). If you don't want to keep this around I think allocating on first non-dumb bo allocation and dropping it when the last such fd closes sounds like a much better idea. Needs a bit more state, you need to track per drm_file whether you've already allocated a non-dumb bo, and a drm_device refcount, but that's not much. Firstopen feels like the wrong thing. Another option would be first_renderopen or something like that, except you can also render on the legacy node and I'm not sure how much there's a demand for this in other drivers. In the end you have open/close callbacks, you can do all the driver specific things you want to do in there. Aside: I kinda also want to ditch lastclose usage. There's fbdev (we have a better solution with Noralf's drm_client for those) and runtime pm (which frankly is just a cheap hack, I want my gpu to susepend also when it's not in use when all the screens are off, not only when I killed X and everything). -Daniel -- Daniel Vetter Software Engineer, Intel Corporation http://blog.ffwll.ch _______________________________________________ dri-devel mailing list dri-devel@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/dri-devel