[alsa-devel] [PATCH] sound: rcar: use fast_io for bus

[Ben Dooks]

The rcar sound driver uses regmap to access registers in various parts
of the block and uses regmap to manage mappings. The regmap is created
without fast_io set, which means it locks with a mutex rather than a
lighter-spinlock.

The use of the mutex lock causes issues when the IRQ handler is entered
as the code needs to read/write register values and thus with lock
debugging enabled the system outputs a number of warnings such as:

BUG: sleeping function called from invalid context at rnel/locking/mutex.c:616

The rcar registers are all connected via APB bus and thus not that slow
to access. The fix is to set the fast_io in the code so that regmap creates
the regmap structures using the faster spinlock functions.

Signed-off-by: Ben Dooks <ben.dooks at codethink.co.uk>
---
 sound/soc/sh/rcar/gen.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/sound/soc/sh/rcar/gen.c b/sound/soc/sh/rcar/gen.c
index 9094970..6468962 100644
--- a/sound/soc/sh/rcar/gen.c
+++ b/sound/soc/sh/rcar/gen.c
@@ -66,6 +66,7 @@ static int rsnd_regmap_read32(void *context,
 }
 
 static struct regmap_bus rsnd_regmap_bus = {
+	.fast_io			= true,
 	.write				= rsnd_regmap_write32,
 	.read				= rsnd_regmap_read32,
 	.reg_format_endian_default	= REGMAP_ENDIAN_NATIVE,
-- 
1.9.0