PCI BARs tell us whether prefetching is safe, but they don't say
anything about write combining (WC). WC changes ordering rules
and allows writes to be collapsed, so it's not safe in general
to use it on a prefetchable region.
Add pci_iomap_wc() and pci_iomap_wc_range() so drivers can take
advantage of write combining when they know it's safe.
On architectures that don't fully support WC, e.g., x86 without
PAT, drivers for legacy framebuffers may get some of the benefit
by using arch_phys_wc_add() in addition to pci_iomap_wc(). But
arch_phys_wc_add() is unreliable and should be avoided in
general. On x86, it uses MTRRs, which are limited in number and
size, so the results will vary based on driver loading order.
The goals of adding pci_iomap_wc() are to:
- Give drivers an architecture-independent way to use WC so they can stop
using interfaces like mtrr_add() (on x86, pci_iomap_wc() uses
PAT when available).
- Move toward using _PAGE_CACHE_MODE_UC, not _PAGE_CACHE_MODE_UC_MINUS,
on x86 on ioremap_nocache() (see de33c442ed ("x86 PAT: fix
performance drop for glx, use UC minus for ioremap(), ioremap_nocache()
and pci_mmap_page_range()").
Signed-off-by: Luis R. Rodriguez <mcgrof@suse.com>
[ Move IORESOURCE_IO check up, space out statements for better readability. ]
Signed-off-by: Borislav Petkov <bp@suse.de>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Cc: <roger.pau@citrix.com>
Cc: <syrjala@sci.fi>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Antonino Daplas <adaplas@gmail.com>
Cc: Bjorn Helgaas <bhelgaas@google.com>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: Dave Airlie <airlied@redhat.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Davidlohr Bueso <dbueso@suse.de>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Jean-Christophe Plagniol-Villard <plagnioj@jcrosoft.com>
Cc: Juergen Gross <jgross@suse.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Michael S. Tsirkin <mst@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Roger Pau Monné <roger.pau@citrix.com>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Stefan Bader <stefan.bader@canonical.com>
Cc: Suresh Siddha <sbsiddha@gmail.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Tomi Valkeinen <tomi.valkeinen@ti.com>
Cc: Toshi Kani <toshi.kani@hp.com>
Cc: Ville Syrjälä <syrjala@sci.fi>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: airlied@linux.ie
Cc: benh@kernel.crashing.org
Cc: dan.j.williams@intel.com
Cc: david.vrabel@citrix.com
Cc: jbeulich@suse.com
Cc: konrad.wilk@oracle.com
Cc: linux-arch@vger.kernel.org
Cc: linux-fbdev@vger.kernel.org
Cc: linux-pci@vger.kernel.org
Cc: venkatesh.pallipadi@intel.com
Cc: vinod.koul@intel.com
Cc: xen-devel@lists.xensource.com
Link: http://lkml.kernel.org/r/1440443613-13696-6-git-send-email-mcgrof@do-not-panic.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Virtio drivers should map the part of the BAR they need, not necessarily
all of it.
Cc: Bjorn Helgaas <bhelgaas@google.com>
Cc: linux-pci@vger.kernel.org
Acked-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
The problem in
commit fea80311a9
Author: Randy Dunlap <rdunlap@xenotime.net>
Date: Sun Jul 24 11:39:14 2011 -0700
iomap: make IOPORT/PCI mapping functions conditional
is that if your architecture supplies pci_iomap/pci_iounmap, it expects
always to supply them. Adding empty body defitions in the !CONFIG_PCI
case, which is what this patch does, breaks the parisc compile because
the functions become doubly defined. It took us a while to spot this,
because we don't actually build !CONFIG_PCI very often (only if someone
is brave enough to test the snake/asp machines).
Since the note in the commit log says this is to fix a
CONFIG_GENERIC_IOMAP issue (which it does because CONFIG_GENERIC_IOMAP
supplies pci_iounmap only if CONFIG_PCI is set), there should actually
have been a condition upon this. This should make sure no other
architecture's !CONFIG_PCI compile breaks in the same way as parisc.
The fix had to be updated to take account of the GENERIC_PCI_IOMAP
separation.
Reported-by: Rolf Eike Beer <eike@sf-mail.de>
Signed-off-by: James Bottomley <JBottomley@Parallels.com>
Some architectures need to override the way
IO port mapping is done on PCI devices.
Supply a generic macro that calls
ioport_map, and make it possible for architectures
to override.
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Many architectures want a generic pci_iomap but
not the rest of iomap.c. Split that to a separate .c
file and add a new config symbol. select automatically
by GENERIC_IOMAP.
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Luis R. Rodriguez
Michael S. Tsirkin
James Bottomley