From 4422c04bbb09f1864e2ce27296457f86d4167fe2 Mon Sep 17 00:00:00 2001 From: Tomi Valkeinen Date: Tue, 14 Dec 2010 14:16:59 +0200 Subject: [PATCH] OMAP: DSS: VRAM: Align start & size of vram to 2M Align the start address and size of VRAM area to 2M as per comments from Russell King: > > So, why SZ_2M? > > Firstly, that's the granularity which we allocate page tables - one > Linux page table covers 2MB of memory. We want to avoid creating page > tables for the main memory mapping as that increases TLB pressure through > the use of additional TLB entries, and more page table walks. > > Plus, we never used to allow the kernel's direct memory mapping to be > mapped at anything less than section size - this restriction has since > been lifted due to OMAP SRAM problems, but I'd rather we stuck with it > to ensure that we have proper behaviour from all parts of the system. > > Secondly, we don't want to end up with lots of fragmentation at the end > of the memory mapping as that'll reduce performance, not only by making > the pfn_valid() search more expensive. > > Emsuring a minimum allocation size and alignment makes sure that the > regions can be coalesced together into one block, and minimises run-time > expenses. > > So please, 2MB, or if you object, at the _very_ _least_ 1MB. But > definitely not PAGE_SIZE. Signed-off-by: Tomi Valkeinen Acked-by: Tony Lindgren --- drivers/video/omap2/vram.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/drivers/video/omap2/vram.c b/drivers/video/omap2/vram.c index 2fd7e5271be9..9441e2eb3dee 100644 --- a/drivers/video/omap2/vram.c +++ b/drivers/video/omap2/vram.c @@ -551,7 +551,7 @@ void __init omap_vram_reserve_sdram_memblock(void) if (!size) return; - size = PAGE_ALIGN(size); + size = ALIGN(size, SZ_2M); if (paddr) { if (paddr & ~PAGE_MASK) { @@ -576,7 +576,7 @@ void __init omap_vram_reserve_sdram_memblock(void) return; } } else { - paddr = memblock_alloc(size, PAGE_SIZE); + paddr = memblock_alloc(size, SZ_2M); } memblock_free(paddr, size); -- GitLab