• Daniel Vetter's avatar
    drm: rip out drm_core_has_MTRR checks · 28185647
    Daniel Vetter authored
    The new arch_phys_wc_add/del functions do the right thing both with
    and without MTRR support in the kernel. So we can drop these
    additional checks.
    
    David Herrmann suggest to also kill the DRIVER_USE_MTRR flag since
    it's now unused, which spurred me to do a bit a better audit of the
    affected drivers. David helped a lot in that. Quoting our mail
    discussion:
    
    On Wed, Jul 10, 2013 at 5:41 PM, David Herrmann <dh.herrmann@gmail.com> wrote:
    > On Wed, Jul 10, 2013 at 5:22 PM, Daniel Vetter <daniel.vetter@ffwll.ch> wrote:
    >> On Wed, Jul 10, 2013 at 3:51 PM, David Herrmann <dh.herrmann@gmail.com> wrote:
    >>>> -#if __OS_HAS_MTRR
    >>>> -static inline int drm_core_has_MTRR(struct drm_device *dev)
    >>>> -{
    >>>> -       return drm_core_check_feature(dev, DRIVER_USE_MTRR);
    >>>> -}
    >>>> -#else
    >>>> -#define drm_core_has_MTRR(dev) (0)
    >>>> -#endif
    >>>> -
    >>>
    >>> That was the last user of DRIVER_USE_MTRR (apart from drivers setting
    >>> it in .driver_features). Any reason to keep it around?
    >>
    >> Yeah, I guess we could rip things out. Which will also force me to
    >> properly audit drivers for the eventual behaviour change this could
    >> entail (in case there's an x86 driver which did not ask for an mtrr,
    >> but iirc there isn't).
    >
    > david@david-mb ~/dev/kernel/linux $ for i in drivers/gpu/drm/* ; do if
    > test -d "$i" ; then if ! grep -q USE_MTRR -r $i ; then echo $i ; fi ;
    > fi ; done
    > drivers/gpu/drm/exynos
    > drivers/gpu/drm/gma500
    > drivers/gpu/drm/i2c
    > drivers/gpu/drm/nouveau
    > drivers/gpu/drm/omapdrm
    > drivers/gpu/drm/qxl
    > drivers/gpu/drm/rcar-du
    > drivers/gpu/drm/shmobile
    > drivers/gpu/drm/tilcdc
    > drivers/gpu/drm/ttm
    > drivers/gpu/drm/udl
    > drivers/gpu/drm/vmwgfx
    > david@david-mb ~/dev/kernel/linux $
    >
    > So for x86 gma500,nouveau,qxl,udl,vmwgfx don't set DRIVER_USE_MTRR.
    > But I cannot tell whether they break if we call arch_phys_wc_add/del,
    > anyway. At least nouveau seemed to work here, but it doesn't use AGP
    > or drm_bufs, I guess.
    
    Cool, thanks a lot for stitching together the list of drivers to look
    at. So for real KMS drivers it's the drives responsibility to add an
    mtrr if it needs one. nouvea, radeon, mgag200, i915 and vmwgfx do that
    already. Somehow the savage driver also ends up doing that, I have no
    idea why.
    
    Note that gma500 as a pure KMS driver doesn't need MTRR setup since
    the platforms that it supports all support PAT. So no MTRRs needed to
    get wc iomappings.
    
    The mtrr support in the drm core is all for legacy mappings of garts,
    framebuffers and registers. All legacy drivers set the USE_MTRR flag,
    so we're good there.
    
    All in all I think we can really just ditch this
    
    /endquote
    
    v2: Also kill DRIVER_USE_MTRR as suggested by David Herrmann
    
    v3: Rebase on top of David Herrmann's agp setup/cleanup changes.
    
    Cc: David Herrmann <dh.herrmann@gmail.com>
    Cc: Andy Lutomirski <luto@amacapital.net>
    Signed-off-by: default avatarDaniel Vetter <daniel.vetter@ffwll.ch>
    Acked-by: default avatarAndy Lutomirski <luto@amacapital.net>
    Reviewed-by: default avatarDavid Herrmann <dh.herrmann@gmail.com>
    Signed-off-by: default avatarDave Airlie <airlied@redhat.com>
    28185647
mgag200_drv.c 3.39 KB