AMS: Return ascodec to interrupt-based I2C2 driver

1. Slightly revised and regularized internal interface. Callback is used
for read and write to provide completion signal instead of having two
mechanisms.

2. Lower overhead for asynchronous or alterate completion callbacks. We
now only init what is required by the transfer. A couple unneeded
structure members were also nixed.

3. Fixes a bug that would neglect a semaphore wait if pumping the I2C
interrupts in a loop when not in thread state or interrupts are masked.

4. Corrects broken initialization order by defining KDEV_INIT, which
makes kernel_init() call kernel_device_init() to initialize additional
devices _after_ the kernel, threading and synchronization objects are
safe to use.

5. Locking set_cpu_frequency has to be done at the highest level in
system.c to ensure the boost counter and the frequency are both set in
agreement. Reconcile the locking inteface between PP and AMS (the only
two currently using locking there) to keep it clean.

Now works fine with voltages in GIT HEAD on my Fuze v2, type 0.
Previously, everything crashed and died instantly. action.c calling
set_cpu_frequency from a tick was part of it. The rest may have been
related to 3. and 4. Honestly, I'm not certain!

Testing by Mihail Zenkov indicates it solves our problems. This will
get the developer builds running again after the kernel assert code
push.

Change-Id: Ie245994fb3e318dd5ef48e383ce61fdd977224d4

1 files changed, 34 insertions, 3 deletions

diff --git a/firmware/target/arm/as3525/system-as3525.c b/firmware/target/arm/as3525/system-as3525.c
index 8aa2d02ab7..0ea0c8fba4 100644
--- a/firmware/target/arm/as3525/system-as3525.c
+++ b/firmware/target/arm/as3525/system-as3525.c
@@ -33,6 +33,8 @@
 #include "backlight-target.h"
 #include "lcd.h"
 
+struct mutex cpufreq_mtx;
+
 /*  Charge Pump and Power management Settings  */
 #define AS314_CP_DCDC3_SETTING    \
                ((0<<7) |  /* CP_SW  Auto-Switch Margin 0=200/300 1=150/255 */  \
@@ -144,6 +146,7 @@ static const struct { int source; void (*isr) (void); } vec_int_srcs[] =
     { INT_SRC_USB, INT_USB_FUNC, },
     { INT_SRC_TIMER1, INT_TIMER1 },
     { INT_SRC_TIMER2, INT_TIMER2 },
+    { INT_SRC_I2C_AUDIO, INT_I2C_AUDIO },
     { INT_SRC_AUDIO, INT_AUDIO },
     /* Lowest priority at the end of the list */
 };
@@ -322,6 +325,12 @@ void system_init(void)
     setup_vic();
 
     dma_init();
+}
+
+/* this is called after kernel and threading are initialized */
+void kernel_device_init(void)
+{
+    mutex_init(&cpufreq_mtx);
 
     ascodec_init();
 
@@ -329,7 +338,8 @@ void system_init(void)
 #ifdef HAVE_AS3543
     /* PLL:       disable audio PLL, we use MCLK already */
     ascodec_write_pmu(0x1A, 7, 0x02);
-    /* DCDC_Cntr: set switching speed of CVDD1/2 power supplies to 1 MHz */
+    /* DCDC_Cntr: set switching speed of CVDD1/2 power supplies to 1 MHz,
+       immediate change */
     ascodec_write_pmu(0x17, 7, 0x30);
     /* Out_Cntr2: set drive strength of 24 MHz and 32 kHz clocks to 1 mA */
     ascodec_write_pmu(0x1A, 2, 0xCC);
@@ -414,11 +424,28 @@ void udelay(unsigned usecs)
 
 #ifndef BOOTLOADER
 #ifdef HAVE_ADJUSTABLE_CPU_FREQ
+bool set_cpu_frequency__lock(void)
+{
+    if (get_processor_mode() != CPU_MODE_THREAD_CONTEXT)
+        return false;
+
+    mutex_lock(&cpufreq_mtx);
+    return true;
+}
+
+void set_cpu_frequency__unlock(void)
+{
+    mutex_unlock(&cpufreq_mtx);
+}
 
 #if CONFIG_CPU == AS3525
 void set_cpu_frequency(long frequency)
 {
-    if(frequency == CPUFREQ_MAX)
+    if (frequency == cpu_frequency)
+    {
+        /* avoid redundant activity */
+    }
+    else if(frequency == CPUFREQ_MAX)
     {
 #ifdef HAVE_ADJUSTABLE_CPU_VOLTAGE
         /* Increasing frequency so boost voltage before change */
@@ -464,7 +491,11 @@ void set_cpu_frequency(long frequency)
 #else   /* as3525v2  */
 void set_cpu_frequency(long frequency)
 {
-    if(frequency == CPUFREQ_MAX)
+    if (frequency == cpu_frequency)
+    {
+        /* avoid redundant activity */
+    }
+    else if(frequency == CPUFREQ_MAX)
     {
 #ifdef HAVE_ADJUSTABLE_CPU_VOLTAGE
         /* Set CVDD1 power supply */