sh: Preparation for uncached jumps through PMB.

Presently most of the 29-bit physical parts do P1/P2 segmentation
with a 1:1 cached/uncached mapping, jumping between the two to
control the caching behaviour. This provides the basic infrastructure
to maintain this behaviour on 32-bit physical parts that don't map
P1/P2 at all, using a shiny new linker section and corresponding
fixmap entry.

Signed-off-by: Stuart Menefy <stuart.menefy@st.com>
Signed-off-by: Paul Mundt <lethal@linux-sh.org>

1 files changed, 15 insertions, 1 deletions

diff --git a/arch/sh/mm/init.c b/arch/sh/mm/init.c
index 79c309780f9..094225e0d72 100644
--- a/arch/sh/mm/init.c
+++ b/arch/sh/mm/init.c
@@ -23,6 +23,7 @@
 
 DEFINE_PER_CPU(struct mmu_gather, mmu_gathers);
 pgd_t swapper_pg_dir[PTRS_PER_PGD];
+unsigned long cached_to_uncached = 0;
 
 void show_mem(void)
 {
@@ -99,7 +100,8 @@ static void set_pte_phys(unsigned long addr, unsigned long phys, pgprot_t prot)
 
 	set_pte(pte, pfn_pte(phys >> PAGE_SHIFT, prot));
 
-	flush_tlb_one(get_asid(), addr);
+	if (cached_to_uncached)
+		flush_tlb_one(get_asid(), addr);
 }
 
 /*
@@ -164,6 +166,18 @@ void __init paging_init(void)
 	}
 
 	free_area_init_nodes(max_zone_pfns);
+
+	/* Set up the uncached fixmap */
+	set_fixmap_nocache(FIX_UNCACHED, __pa(&__uncached_start));
+
+#ifdef CONFIG_29BIT
+	/*
+	 * Handle trivial transitions between cached and uncached
+	 * segments, making use of the 1:1 mapping relationship in
+	 * 512MB lowmem.
+	 */
+	cached_to_uncached = P2SEG - P1SEG;
+#endif
 }
 
 static struct kcore_list kcore_mem, kcore_vmalloc;