From mboxrd@z Thu Jan 1 00:00:00 1970 From: dwmw2@infradead.org (David Woodhouse) Date: Thu, 16 Mar 2017 12:17:27 +0000 Subject: [PATCH v2] arm64: pci: add support for pci_mmap_page_range In-Reply-To: <20160415130953.GI22906@arm.com> References: <1460581856-12380-1-git-send-email-jerin.jacob@caviumnetworks.com> <20160415130953.GI22906@arm.com> Message-ID: <1489666647.4195.238.camel@infradead.org> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On Fri, 2016-04-15 at 14:09 +0100, Will Deacon wrote: > > > +?????if (write_combine) > > +?????????????vma->vm_page_prot = pgprot_writecombine(vma->vm_page_prot); > > +?????else > > +?????????????vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot); > > For consistency with ioremap, this should be pgprot_device. What's the difference? I note that VFIO is using pgprot_noncached() too, in vfio_pci_mmap() ? where it open-codes an entirely arch-agnostic version of pci_mmap_page_range() all for itself. Should that be changed to pgprot_device() too? Let me see if I can get this straight... We have the legacy interface through /proc/bus/pci, where the user passes a "user-visible" bus address not necessarily (on platforms with HAVE_PCI_RESOURCE_TO_USER) a host physical address. The arch-specific pci_mmap_page_range() exists to work around that translation, on the two platforms which need it. It *also* has (on about three platforms) support for a write-combining mapping. The sysfs interface theough /sys/bus/pci/devices/*/resource* probably doesn't need to use pci_mmap_page_range() at all, *except* for the 'resourceX_wc' variant which has write-combining support. How about we do the following (probably not in this order): ?? Kill pci_mmap_page_range() entirely. ?? Implement a generic version which has (arch-assisted) WC support ? ?but no knowledge of the horrid pci_resource_to_user() mapping. ?? Require pci_user_to_resource() to be provided by platforms with ? ?HAVE_ARCH_PCI_RESOURCE_TO_USER, and call that from *generic* code, ? ?for the legacy procfs interface, before invoking the generic ? ?replacement for pci_mmap_page_range(). (Yes, we still need to support mmap of I/O resources on... is it only powerpc? And there are a few inconsistencies, like powerpc forcing WC even on the sysfs files that *don't* have _wc in their name, that probably want to be cleaned up as we consolidate...) -------------- next part -------------- A non-text attachment was scrubbed... Name: smime.p7s Type: application/x-pkcs7-signature Size: 4938 bytes Desc: not available URL: