Skip updating the kmap_pte and flushing the TLB if the pte we
are about to write is the same as the one we wrote last time we
called kmap_atomic for this km_type.
Also expose the flags to allow a caller to specify their own
flags for things like non-cacheable IO memory.
---
This is the starts of some work Ben and I were discussion to allow us to
use kmap_atomic to access a page size region of PCI CFG space when its
provided as direct MMIO.
We also intend to provide a means to preload the TLB for SW managed TLB
machines.
- k
include/asm-powerpc/highmem.h | 16 +++++++++++++---
1 files changed, 13 insertions(+), 3 deletions(-)
diff --git a/include/asm-powerpc/highmem.h b/include/asm-powerpc/highmem.h
index f7b21ee..a50bb00 100644
--- a/include/asm-powerpc/highmem.h
+++ b/include/asm-powerpc/highmem.h
@@ -73,10 +73,12 @@ static inline void kunmap(struct page *page)
* be used in IRQ contexts, so in some (very limited) cases we need
* it.
*/
-static inline void *kmap_atomic(struct page *page, enum km_type type)
+static inline void *__kmap_atomic(struct page *page,
+ enum km_type type, unsigned long flags)
{
unsigned int idx;
unsigned long vaddr;
+ pte_t pte;
/* even !CONFIG_PREEMPT needs this, for in_atomic in do_page_fault */
pagefault_disable();
@@ -88,12 +90,20 @@ static inline void *kmap_atomic(struct page *page, enum
km_type type)
#ifdef HIGHMEM_DEBUG
BUG_ON(!pte_none(*(kmap_pte+idx)));
#endif
- set_pte_at(&init_mm, vaddr, kmap_pte+idx, mk_pte(page, kmap_prot));
- flush_tlb_page(NULL, vaddr);
+ pte = mk_pte(page, flags);
+ if (!pte_same(kmap_pte[idx], pte)) {
+ set_pte_at(&init_mm, vaddr, kmap_pte+idx, pte);
+ flush_tlb_page(NULL, vaddr);
+ }
return (void*) vaddr;
}
+static inline void *kmap_atomic(struct page *page, enum km_type type)
+{
+ return __kmap_atomic(page, type, kmap_prot);
+}
+
static inline void kunmap_atomic(void *kvaddr, enum km_type type)
{
#ifdef HIGHMEM_DEBUG
--
1.5.3.4
_______________________________________________
Linuxppc-dev mailing list
Linuxppc-dev@ozlabs.org
https://ozlabs.org/mailman/listinfo/linuxppc-dev
