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Subject[PATCH] powerpc/8xx: Simplify pte_update() with 16k pages
Date
While looking at code generated for code patching, I saw that
pte_clear generated:

2d8: 38 a0 00 00 li r5,0
2dc: 38 e0 10 00 li r7,4096
2e0: 39 00 20 00 li r8,8192
2e4: 39 40 30 00 li r10,12288
2e8: 90 a9 00 00 stw r5,0(r9)
2ec: 90 e9 00 04 stw r7,4(r9)
2f0: 91 09 00 08 stw r8,8(r9)
2f4: 91 49 00 0c stw r10,12(r9)

With 16k pages, only the first entry is used by the kernel, so no need
to adapt the address of other entries. Only duplicate the first entry
for hardware.

Now it is:

2cc: 39 40 00 00 li r10,0
2d0: 91 49 00 00 stw r10,0(r9)
2d4: 91 49 00 04 stw r10,4(r9)
2d8: 91 49 00 08 stw r10,8(r9)
2dc: 91 49 00 0c stw r10,12(r9)

Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
---
arch/powerpc/include/asm/nohash/32/pgtable.h | 10 ++++++++--
1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/arch/powerpc/include/asm/nohash/32/pgtable.h b/arch/powerpc/include/asm/nohash/32/pgtable.h
index 9091e4904a6b..981e414bdeef 100644
--- a/arch/powerpc/include/asm/nohash/32/pgtable.h
+++ b/arch/powerpc/include/asm/nohash/32/pgtable.h
@@ -256,8 +256,14 @@ static inline pte_basic_t pte_update(struct mm_struct *mm, unsigned long addr, p

num = number_of_cells_per_pte(pmd, new, huge);

- for (i = 0; i < num; i++, entry++, new += SZ_4K)
- *entry = new;
+ for (i = 0; i < num; i += PAGE_SIZE / SZ_4K, new += PAGE_SIZE) {
+ *entry++ = new;
+ if (IS_ENABLED(CONFIG_PPC_16K_PAGES) && num != 1) {
+ *entry++ = new;
+ *entry++ = new;
+ *entry++ = new;
+ }
+ }

return old;
}
--
2.37.1
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