ALSA: hda: Direct MMIO accesses

HD-audio drivers access to the mmio registers indirectly via the
corresponding bus->io_ops callbacks.  This is because some platform
(notably Tegra SoC) requires the word-aligned access.  But it's rather
a rare case, and other platforms suffer from the penalties by indirect
calls unnecessarily.

This patch is an attempt to optimize and cleanup for this situation.
Now the special aligned access is used only when a new kconfig
CONFIG_SND_HDA_ALIGNED_MMIO is set.  And the HD-audio core itself
provides the aligned MMIO access helpers instead of the driver side.
If Kconfig isn't set (as default), the standard helpers like readl()
or writel() are used directly.

A couple of places in ASoC Intel drivers have the access via io_ops
reg_writel(), and they are replaced with the direct writel() calls.

And now with this patch, the whole bus->io_ops becomes empty, so it's
dropped completely.  The bus initialization functions are changed
accordingly as well to drop the whole bus->io_ops.

Reviewed-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>

1 files changed, 1 insertions, 0 deletions

diff --git a/sound/pci/hda/Kconfig b/sound/pci/hda/Kconfig
index 35d934309cb2..82198ea8f7f8 100644
--- a/sound/pci/hda/Kconfig
+++ b/sound/pci/hda/Kconfig
@@ -26,6 +26,7 @@ config SND_HDA_TEGRA
 	tristate "NVIDIA Tegra HD Audio"
 	depends on ARCH_TEGRA
 	select SND_HDA
+	select SND_HDA_ALIGNED_MMIO
 	help
 	  Say Y here to support the HDA controller present in NVIDIA
 	  Tegra SoCs