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| author | Suresh Siddha <suresh.b.siddha@intel.com> | 2008-04-25 17:07:22 -0700 |
|---|---|---|
| committer | Ingo Molnar <mingo@elte.hu> | 2008-04-30 23:15:35 +0200 |
| commit | de33c442ed2a465d2d7804b26dafd2eec067aa34 (patch) | |
| tree | 02a9cb2b96d0ad535f0dbfbdccc35afe21aa052e /arch/x86/pci | |
| parent | b9b39bfba5b0de3418305f01cfa7bc55a16004e1 (diff) | |
| download | linux-de33c442ed2a465d2d7804b26dafd2eec067aa34.tar.gz linux-de33c442ed2a465d2d7804b26dafd2eec067aa34.tar.bz2 linux-de33c442ed2a465d2d7804b26dafd2eec067aa34.zip | |
x86 PAT: fix performance drop for glx, use UC minus for ioremap(), ioremap_nocache() and pci_mmap_page_range()
Use UC_MINUS for ioremap(), ioremap_nocache() instead of strong UC.
Once all the X drivers move to ioremap_wc(), we can go back to strong
UC semantics for ioremap() and ioremap_nocache().
To avoid attribute aliasing issues, pci_mmap_page_range() will also
use UC_MINUS for default non write-combining mapping request.
Next steps:
a) change all the video drivers using ioremap() or ioremap_nocache()
and adding WC MTTR using mttr_add() to ioremap_wc()
b) for strict usage, we can go back to strong uc semantics
for ioremap() and ioremap_nocache() after some grace period for
completing step-a.
c) user level X server needs to use the appropriate method for setting
up WC mapping (like using resourceX_wc sysfs file instead of
adding MTRR for WC and using /dev/mem or resourceX under /sys)
Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
Signed-off-by: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Diffstat (limited to 'arch/x86/pci')
| -rw-r--r-- | arch/x86/pci/i386.c | 12 |
1 files changed, 9 insertions, 3 deletions
diff --git a/arch/x86/pci/i386.c b/arch/x86/pci/i386.c index 94f6c73a53d0..8af0f0bae2af 100644 --- a/arch/x86/pci/i386.c +++ b/arch/x86/pci/i386.c @@ -301,6 +301,13 @@ int pci_mmap_page_range(struct pci_dev *dev, struct vm_area_struct *vma, prot = pgprot_val(vma->vm_page_prot); if (pat_wc_enabled && write_combine) prot |= _PAGE_CACHE_WC; + else if (pat_wc_enabled) + /* + * ioremap() and ioremap_nocache() defaults to UC MINUS for now. + * To avoid attribute conflicts, request UC MINUS here + * aswell. + */ + prot |= _PAGE_CACHE_UC_MINUS; else if (boot_cpu_data.x86 > 3) prot |= _PAGE_CACHE_UC; @@ -319,9 +326,8 @@ int pci_mmap_page_range(struct pci_dev *dev, struct vm_area_struct *vma, * - request is uncached, return cannot be write-combine * - request is write-combine, return cannot be write-back */ - if ((flags == _PAGE_CACHE_UC && - (new_flags == _PAGE_CACHE_WB || - new_flags == _PAGE_CACHE_WC)) || + if ((flags == _PAGE_CACHE_UC_MINUS && + (new_flags == _PAGE_CACHE_WB)) || (flags == _PAGE_CACHE_WC && new_flags == _PAGE_CACHE_WB)) { free_memtype(addr, addr+len); |