[PATCH] ALSA: sh: aica: Fix spu_memset() stride

[PATCH] ALSA: sh: aica: Fix spu_memset() stride

[Florian Fuchs]

spu_memset() writes one 32-bit word per iteration, but advances the
destination offset by only one byte. spu_reset() calls it with
0x200000 / 4 words to clear the 2 MiB of sound RAM, so:

 - three out of four writel() calls target an unaligned address. The
   SH4 can't do that. Each one traps and is emulated by the unaligned
   access fixup. This call to spu_memset() causes 393216 unaligned
   accesses, visible in /proc/cpu/alignment.
 - the clear covered only about 512 KiB of sound RAM, not 2 MiB.

Advance the offset by the size of the written word, to clear the full
sound RAM using aligned writes.

Fixes: 198de43d758c ("[ALSA] Add ALSA support for the SEGA Dreamcast PCM device")
Signed-off-by: Florian Fuchs <fuchsfl@gmail.com>
---
The patch has been tested on the hardware and sound is also still
working well, the boot is faster by about 4s due to less unaligned
fixups.

Previously: 7.9s to boot:
[    2.900000] AICA AICA: ALSA Driver for Yamaha AICA Super Intelligent Sound Processor
..
[    7.872000] ALSA device list:
[    7.876000]   #1: Yamaha AICA Super Intelligent Sound Processor for SEGA Dreamcast

After: 3.8s to boot:
[    2.892000] AICA AICA: ALSA Driver for Yamaha AICA Super Intelligent Sound Processor
..
[    3.796000] ALSA device list:
[    3.800000]   #1: Yamaha AICA Super Intelligent Sound Processor for SEGA Dreamcast

 sound/sh/aica.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/sound/sh/aica.c b/sound/sh/aica.c
index 078fc7fc08f9..04f80c8c89c0 100644
--- a/sound/sh/aica.c
+++ b/sound/sh/aica.c
@@ -94,7 +94,7 @@ static void spu_memset(u32 toi, u32 what, int length)
 		local_irq_save(flags);
 		writel(what, toi + SPU_MEMORY_BASE);
 		local_irq_restore(flags);
-		toi++;
+		toi += sizeof(what);
 	}
 }
 

base-commit: c1b1c25de0d6008c3fcabc942fba635ea3693c3f
-- 
2.43.0