Gigabeat S/i.MX31: Take care of an interrupt priority inversion that can happen during PCM callback lockout when DVFS switches frequecies during the lockout, preventing a thread from unlocking the callback until DVFS finishes, causing an SSI FIFO underrun. Hadn't thought of an acceptable way to deal with it before.

git-svn-id: svn://svn.rockbox.org/rockbox/trunk@28996 a1c6a512-1295-4272-9138-f99709370657

firmware/target/arm/imx31/avic-imx31.h

@@ -67,6 +67,11 @@ void avic_set_int_type(enum IMX31_INT_LIST ints, enum INT_TYPE intstype);
 #define AVIC_NIL_ENABLE  (-1)
 void avic_set_ni_level(int level);
 
+static inline void avic_mask_int(enum IMX31_INT_LIST ints)
+    { AVIC_INTDISNUM = ints; }
+
+static inline void avic_unmask_int(enum IMX31_INT_LIST ints)
+    { AVIC_INTENNUM = ints; }
 
 /* Call a service routine while allowing preemption by interrupts of higher
  * priority. Avoid using any app or other SVC stack by doing it with a mini

firmware/target/arm/imx31/dvfs_dptc-imx31.c

@@ -612,6 +612,22 @@ void dvfs_dptc_stop(void)
 }
 
 
+/* Mask the DVFS interrupt without affecting running status */
+void dvfs_int_mask(bool mask)
+{
+    if (mask)
+    {
+        /* Just disable, not running = already disabled */
+        avic_mask_int(INT_CCM_DVFS);
+    }
+    else if (dvfs_running)
+    {
+        /* DVFS is running; unmask it */
+        avic_unmask_int(INT_CCM_DVFS);
+    }
+}
+
+
 /* Set a signal load tracking weight */
 void dvfs_set_lt_weight(enum DVFS_LT_SIGS index, unsigned long value)
 {

firmware/target/arm/imx31/dvfs_dptc-imx31.h

@@ -128,6 +128,7 @@ void dvfs_wfi_monitor(bool on);
 void dvfs_set_lt_weight(enum DVFS_LT_SIGS index, unsigned long value);
 void dvfs_set_lt_detect(enum DVFS_LT_SIGS index, bool edge);
 void dvfs_set_gp_bit(enum DVFS_DVGPS dvgp, bool assert);
+void dvfs_int_mask(bool mask);
 
 unsigned int dvfs_dptc_get_voltage(void);
 unsigned int dvfs_get_level(void);

firmware/target/arm/imx31/gigabeat-s/kernel-gigabeat-s.c

@@ -85,3 +85,8 @@ void tick_stop(void)
     ccm_module_clock_gating(CG_EPIT1, CGM_OFF); /* Turn off module clock */
 }
 
+
+void kernel_audio_locking(bool locking)
+{
+    dvfs_int_mask(locking);
+}

firmware/target/arm/imx31/gigabeat-s/pcm-gigabeat-s.c

@@ -109,12 +109,22 @@ static void play_dma_callback(void)
 
 void pcm_play_lock(void)
 {
+    /* Need to prevent DVFS from causing interrupt priority inversion if audio
+     * is locked and a DVFS interrupt fires, blocking reenabling of audio by a 
+     * low-priority mode for at least the duration of the lengthy DVFS routine.
+     * Not really an issue with state changes but lockout when playing.
+     *
+     * Keep direct use of DVFS code away from here though. This could provide
+     * more services in the future anyway. */
+    kernel_audio_locking(true);
     ++dma_play_data.locked;
 }
 
 void pcm_play_unlock(void)
 {
-    if (--dma_play_data.locked == 0 && dma_play_data.state != 0)
+    if (--dma_play_data.locked == 0)
+    {
+        if (dma_play_data.state != 0)
         {
             int oldstatus = disable_irq_save();
             int pending = dma_play_data.callback_pending;
@@ -124,6 +134,9 @@ void pcm_play_unlock(void)
             if (pending != 0)
                 play_dma_callback();
         }
+
+        kernel_audio_locking(false);
+    }
 }
 
 void pcm_dma_apply_settings(void)
@@ -442,12 +455,15 @@ static void rec_dma_callback(void)
 
 void pcm_rec_lock(void)
 {
+    kernel_audio_locking(true);    
     ++dma_rec_data.locked;
 }
 
 void pcm_rec_unlock(void)
 {
-    if (--dma_rec_data.locked == 0 && dma_rec_data.state != 0)
+    if (--dma_rec_data.locked == 0)
+    {
+        if (dma_rec_data.state != 0)
         {
             int oldstatus = disable_irq_save();
             int pending = dma_rec_data.callback_pending;
@@ -457,6 +473,9 @@ void pcm_rec_unlock(void)
             if (pending != 0)
                 rec_dma_callback();
         }
+
+        kernel_audio_locking(false);
+    }
 }
 
 void pcm_rec_dma_stop(void)

firmware/target/arm/imx31/gigabeat-s/system-target.h

@@ -51,6 +51,9 @@ void tick_stop(void);
 void kernel_device_init(void);
 void system_halt(void);
 
+/* Handle some audio lockout related tasks */
+void kernel_audio_locking(bool locking);
+
 #define KDEV_INIT
 
 struct ARM_REGS {