It was observed on a mx31pdk board that audio playback only worked when the bootloader was Redboot, and 
did not work when U-boot was used. 

Comparing the sources of these bootloaders showed that the AIPS registers were not setup in U-boot.

Instead of relying on the bootloader to setup the AIPS registers, do it in the kernel so that audio
playback can work independantly of the bootloader being used.

Copied the AIPS settings from Redboot to the kernel.

Signed-off-by: Fabio Estevam <redacted>
---
Changes since v1:
- Make sure post_cpu_init() only runs on mx31
- Place imx_set_aips() in a common location so that other SoCs can use it.
- Improve comments about OPACRx

 arch/arm/mach-imx/cpu-imx31.c           |   11 +++++++++++
 arch/arm/plat-mxc/cpu.c                 |   24 ++++++++++++++++++++++++
 arch/arm/plat-mxc/include/mach/common.h |    1 +
 3 files changed, 36 insertions(+), 0 deletions(-)

diff --git a/arch/arm/mach-imx/cpu-imx31.c b/arch/arm/mach-imx/cpu-imx31.c
index 3f2345f..8841039 100644
--- a/arch/arm/mach-imx/cpu-imx31.c
+++ b/arch/arm/mach-imx/cpu-imx31.c

@@ -60,3 +60,14 @@ int mx31_revision(void)
 	return mx31_cpu_rev;
 }
 EXPORT_SYMBOL(mx31_revision);
+
+static int __init post_cpu_init(void)
+{
+	if (cpu_is_mx31()) {
+		imx_set_aips(MX31_IO_ADDRESS(MX31_AIPS1_BASE_ADDR));
+		imx_set_aips(MX31_IO_ADDRESS(MX31_AIPS2_BASE_ADDR));
+	}
+
+	return 0;
+}
+postcore_initcall(post_cpu_init);