I'm not sure I understand the intent of the previous behavior. mmap on /dev/agpgart and DRM_AGP maps had no cache flags set, so they would be fully cacheable. But the DRM code (most of the time) would add a write-combining MTRR that would change the effective memory type to WC.
The new behavior just requests WC explicitly for all AGP maps.
If there is any code out there that expects cacheable access to the AGP aperture (because the drm driver doesn't request an MTRR or because it's using /dev/agpgart directly), then it will now end up with a UC or WC mapping, depending on the architecture and PAT availability. But cacheable access to the aperture seems like it's asking for trouble, because, AIUI, the aperture is an alias of RAM.
Signed-off-by: Andy Lutomirski luto@amacapital.net ---
It's conceivable that libpciaccess could have issues with this due to memtype conflicts, but I think this is unlikely (as long as a WC mapping gets there first, I think the conflict resolution rules will all work out). In any case, everything that maps the AGP aperture ought to be using /dev/agpgart or the DRM API, in which case everything should be okay.
I don't have anything with an AGP slot to test AFAIK.
drivers/char/agp/frontend.c | 8 +++++--- drivers/gpu/drm/drm_pci.c | 8 ++++---- drivers/gpu/drm/drm_stub.c | 10 ++-------- drivers/gpu/drm/drm_vm.c | 11 ++++------- 4 files changed, 15 insertions(+), 22 deletions(-)
diff --git a/drivers/char/agp/frontend.c b/drivers/char/agp/frontend.c index 2e04433..1b19239 100644 --- a/drivers/char/agp/frontend.c +++ b/drivers/char/agp/frontend.c @@ -603,7 +603,8 @@ static int agp_mmap(struct file *file, struct vm_area_struct *vma) vma->vm_ops = kerninfo.vm_ops; } else if (io_remap_pfn_range(vma, vma->vm_start, (kerninfo.aper_base + offset) >> PAGE_SHIFT, - size, vma->vm_page_prot)) { + size, + pgprot_writecombine(vma->vm_page_prot))) { goto out_again; } mutex_unlock(&(agp_fe.agp_mutex)); @@ -618,8 +619,9 @@ static int agp_mmap(struct file *file, struct vm_area_struct *vma) if (kerninfo.vm_ops) { vma->vm_ops = kerninfo.vm_ops; } else if (io_remap_pfn_range(vma, vma->vm_start, - kerninfo.aper_base >> PAGE_SHIFT, - size, vma->vm_page_prot)) { + kerninfo.aper_base >> PAGE_SHIFT, + size, + pgprot_writecombine(vma->vm_page_prot))) { goto out_again; } mutex_unlock(&(agp_fe.agp_mutex)); diff --git a/drivers/gpu/drm/drm_pci.c b/drivers/gpu/drm/drm_pci.c index bd719e9..d0f6699 100644 --- a/drivers/gpu/drm/drm_pci.c +++ b/drivers/gpu/drm/drm_pci.c @@ -278,10 +278,10 @@ int drm_pci_agp_init(struct drm_device *dev) } if (drm_core_has_MTRR(dev)) { if (dev->agp) - dev->agp->agp_mtrr = - mtrr_add(dev->agp->agp_info.aper_base, - dev->agp->agp_info.aper_size * - 1024 * 1024, MTRR_TYPE_WRCOMB, 1); + dev->agp->agp_mtrr = arch_phys_wc_add( + dev->agp->agp_info.aper_base, + dev->agp->agp_info.aper_size * + 1024 * 1024); } } return 0; diff --git a/drivers/gpu/drm/drm_stub.c b/drivers/gpu/drm/drm_stub.c index 7d30802..9e2acdf 100644 --- a/drivers/gpu/drm/drm_stub.c +++ b/drivers/gpu/drm/drm_stub.c @@ -451,14 +451,8 @@ void drm_put_dev(struct drm_device *dev)
drm_lastclose(dev);
- if (drm_core_has_MTRR(dev) && drm_core_has_AGP(dev) && - dev->agp && dev->agp->agp_mtrr >= 0) { - int retval; - retval = mtrr_del(dev->agp->agp_mtrr, - dev->agp->agp_info.aper_base, - dev->agp->agp_info.aper_size * 1024 * 1024); - DRM_DEBUG("mtrr_del=%d\n", retval); - } + if (drm_core_has_MTRR(dev) && drm_core_has_AGP(dev) && dev->agp) + arch_phys_wc_del(dev->agp->agp_mtrr);
if (dev->driver->unload) dev->driver->unload(dev); diff --git a/drivers/gpu/drm/drm_vm.c b/drivers/gpu/drm/drm_vm.c index 163f436..b1e4ec8 100644 --- a/drivers/gpu/drm/drm_vm.c +++ b/drivers/gpu/drm/drm_vm.c @@ -49,13 +49,10 @@ static pgprot_t drm_io_prot(struct drm_local_map *map, pgprot_t tmp = vm_get_page_prot(vma->vm_flags);
#if defined(__i386__) || defined(__x86_64__) - if (map->type != _DRM_AGP) { - if (map->type == _DRM_FRAME_BUFFER || - map->flags & _DRM_WRITE_COMBINING) - tmp = pgprot_writecombine(tmp); - else - tmp = pgprot_noncached(tmp); - } + if (map->type == _DRM_REGISTERS && !(map->flags & _DRM_WRITE_COMBINING)) + tmp = pgprot_noncached(tmp); + else + tmp = pgprot_writecombine(tmp); #elif defined(__powerpc__) pgprot_val(tmp) |= _PAGE_NO_CACHE; if (map_type == _DRM_REGISTERS)