Re: [PATCH 57/59] drm/ast: Use managed pci functions

[Daniel Vetter <daniel.vetter@ffwll.ch>]

On Wed, Apr 15, 2020 at 10:17 AM Daniel Vetter <daniel.vetter@ffwll.ch> wrote:
>
> On Wed, Apr 15, 2020 at 10:09 AM Daniel Vetter <daniel.vetter@ffwll.ch> wrote:
> >
> > On Wed, Apr 15, 2020 at 9:52 AM Thomas Zimmermann <tzimmermann@suse.de> wrote:
> > >
> > > Hi Daniel
> > >
> > > Am 15.04.20 um 09:40 schrieb Daniel Vetter:
> > > > Allows us to remove a bit of cleanup code.
> > > >
> > > > Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
> > > > Cc: Dave Airlie <airlied@redhat.com>
> > > > Cc: Thomas Zimmermann <tzimmermann@suse.de>
> > > > Cc: Gerd Hoffmann <kraxel@redhat.com>
> > > > Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
> > > > Cc: Emil Velikov <emil.velikov@collabora.com>
> > > > Cc: "Noralf Trønnes" <noralf@tronnes.org>
> > > > Cc: Sam Ravnborg <sam@ravnborg.org>
> > > > Cc: "Christian König" <christian.koenig@amd.com>
> > > > Cc: "Y.C. Chen" <yc_chen@aspeedtech.com>
> > > > ---
> > > >  drivers/gpu/drm/ast/ast_drv.c  | 10 +++-------
> > > >  drivers/gpu/drm/ast/ast_main.c |  3 ---
> > > >  2 files changed, 3 insertions(+), 10 deletions(-)
> > > >
> > > > diff --git a/drivers/gpu/drm/ast/ast_drv.c b/drivers/gpu/drm/ast/ast_drv.c
> > > > index b7ba22dddcad..48a9cc4e080a 100644
> > > > --- a/drivers/gpu/drm/ast/ast_drv.c
> > > > +++ b/drivers/gpu/drm/ast/ast_drv.c
> > > > @@ -91,15 +91,13 @@ static int ast_pci_probe(struct pci_dev *pdev, const struct pci_device_id *ent)
> > > >
> > > >       ast_kick_out_firmware_fb(pdev);
> > > >
> > > > -     ret = pci_enable_device(pdev);
> > > > +     ret = pcim_enable_device(pdev);
> > > >       if (ret)
> > > >               return ret;
> > > >
> > > >       dev = drm_dev_alloc(&driver, &pdev->dev);
> > > > -     if (IS_ERR(dev)) {
> > > > -             ret = PTR_ERR(dev);
> > > > -             goto err_pci_disable_device;
> > > > -     }
> > > > +     if (IS_ERR(dev))
> > > > +             return  PTR_ERR(dev);
> > > >
> > > >       dev->pdev = pdev;
> > > >       pci_set_drvdata(pdev, dev);
> > > > @@ -120,8 +118,6 @@ static int ast_pci_probe(struct pci_dev *pdev, const struct pci_device_id *ent)
> > > >       ast_driver_unload(dev);
> > > >  err_drm_dev_put:
> > > >       drm_dev_put(dev);
> > > > -err_pci_disable_device:
> > > > -     pci_disable_device(pdev);
> > > >       return ret;
> > > >
> > > >  }
> > > > diff --git a/drivers/gpu/drm/ast/ast_main.c b/drivers/gpu/drm/ast/ast_main.c
> > > > index e5398e3dabe7..1b35728ad871 100644
> > > > --- a/drivers/gpu/drm/ast/ast_main.c
> > > > +++ b/drivers/gpu/drm/ast/ast_main.c
> > > > @@ -531,8 +531,5 @@ void ast_driver_unload(struct drm_device *dev)
> > > >       drm_mode_config_cleanup(dev);
> > > >
> > > >       ast_mm_fini(ast);
> > > > -     if (ast->ioregs != ast->regs + AST_IO_MM_OFFSET)
> > > > -             pci_iounmap(dev->pdev, ast->ioregs);
> > > > -     pci_iounmap(dev->pdev, ast->regs);
> > >
> > > This gets unmapped as part of the automatic pci_disable_device(), I guess?
> >
> > Yup, once you go with pcim_enable_device all pci_ functions on that
> > device become manged and auto-cleanup.
> >
> > > Do we need drm_dev_enter()/_exit() to make I/O work reliably?
> >
> > That does nothing without drm_dev_unplug(), which has the annoying
> > side effect that it also shuts up stuff like
> > drm_atomic_helper_shutdown for module unload. And developers really
> > want their devices to be shut off on driver unload. So yeah
> > unfortunately we currently can decide between "correct for hotunplug"
> > and "convenient for driver unload for driver authors". I'm not sure
> > what to best do here, since all options are kinda not great for one
> > use-case or the other.
>
> So if we'd split up drm_dev_unplug into drm_dev_unregister +
> drm_dev_mark_unplugged or whatever the options would be:
>
> drm_atomic_helper_shutdown(); /* and other hw shut down */
> drm_dev_unregister();
> drm_dev_mark_unplugged();
>
> Kinda annoying since userspace might race with us, so we might still
> have an active fb (in sw tracking at least) that we need to clean up
> again later on. Plus shutting down hw before we unregister is going to
> make the hotunplug confusion for userspace even more a mess.
>
> Next option:
> drm_dev_unregster();
> /* shut down hw */
> drm_dev_mark_unplugged();
>
> This just wastes time since if we're really unplugged we'll do lots of
> io attempts that go nowhere because the device is gone already.
> They'll all time out (if the bus subsystem/hw for our driver works
> correctly at least). Plus userspace can still sneak in and do stupid
> stuff I think while we're not looking.
>
> Next up:
> drm_dev_unregister();
> drm_dev_mark_unplugged();
> drm_atomic_helper_shutdown();
>
> This is a bit silly since all the shutdown code now does is shut down
> sw state, and never touches hw (if the driver is fully annotated with
> drm_dev_enter/exit).
>
> One option might be that we slap a lot more drm_dev_enter/exit around
> the top-level ioctls (to at least stop the userspace races with driver
> unload), and allow drivers to still shut down stuff internally.
>
> tldr; it's all still a bit a mess.

Adding Laurent, I just discussed this a bit with him on irc.
-Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch
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