i.MX31: Remove long udelay from DVFS interrupt handler

Split the ISR into two parts and alllow quick return from first half.

Introduces a uevent() API to have a callback happen in a specified
number of microseconds. Right now only one event is supported.

Change-Id: Ib1666165be2f6082e5275d64961f083cab104f9f

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

@@ -56,7 +56,7 @@ void INIT_ATTR tick_start(unsigned int interval_in_ms)
     EPITCR1 = EPITCR_CLKSRC_IPG_CLK | EPITCR_WAITEN | EPITCR_IOVW |
               ((2640-1) << EPITCR_PRESCALER_POS) | EPITCR_RLD |
               EPITCR_OCIEN | EPITCR_ENMOD;
- 
+
     EPITLR1 = interval_in_ms*25; /* Count down from interval */
     EPITCMPR1 = 0;               /* Event when counter reaches 0 */
     EPITSR1 = EPITSR_OCIF;       /* Clear any pending interrupt */
@@ -86,9 +86,3 @@ void tick_stop(void)
     EPITSR1 = EPITSR_OCIF;                  /* Clear pending */
     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

@@ -104,7 +104,7 @@ static void play_dma_callback(void)
                   PCM_DMAST_ERR_DMA : PCM_DMAST_OK;
     const void *addr;
     size_t size;
-    
+
     if (pcm_play_dma_complete_callback(status, &addr, &size))
     {
         play_start_dma(addr, size);
@@ -114,33 +114,20 @@ 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)
+    if (--dma_play_data.locked == 0 && dma_play_data.state != 0)
     {
-        if (dma_play_data.state != 0)
-        {
-            int oldstatus = disable_irq_save();
-            int pending = dma_play_data.callback_pending;
-            dma_play_data.callback_pending = 0;
-            restore_irq(oldstatus);
+        int oldstatus = disable_irq_save();
+        int pending = dma_play_data.callback_pending;
+        dma_play_data.callback_pending = 0;
+        restore_irq(oldstatus);
 
-            if (pending != 0)
-                play_dma_callback();
-        }
-
-        kernel_audio_locking(false);
+        if (pending != 0)
+            play_dma_callback();
     }
 }
 
@@ -368,26 +355,20 @@ 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)
+    if (--dma_rec_data.locked == 0 && dma_rec_data.state != 0)
     {
-        if (dma_rec_data.state != 0)
-        {
-            int oldstatus = disable_irq_save();
-            int pending = dma_rec_data.callback_pending;
-            dma_rec_data.callback_pending = 0;
-            restore_irq(oldstatus);
+        int oldstatus = disable_irq_save();
+        int pending = dma_rec_data.callback_pending;
+        dma_rec_data.callback_pending = 0;
+        restore_irq(oldstatus);
 
-            if (pending != 0)
-                rec_dma_callback();
-        }
-
-        kernel_audio_locking(false);
+        if (pending != 0)
+            rec_dma_callback();
     }
 }
 

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

@@ -84,7 +84,62 @@ void watchdog_service(void)
     WDOG_WSR = 0xaaaa;
 }
 
-/** GPT timer routines - basis for udelay **/
+
+/** uevent APIs **/
+
+static void (*ucallback)(void) = NULL; /* uevent callback */
+
+static void cancel_uevent(void)
+{
+    GPTSR = GPTSR_OF1;
+    GPTIR &= ~GPTIR_OF1IE;
+    ucallback = NULL;
+}
+
+static void __attribute__((interrupt("IRQ"))) GPT_HANDLER(void)
+{
+    uevent_cb_type cb = ucallback;
+    cancel_uevent();
+    cb();
+}
+
+void uevent(unsigned long usecs, uevent_cb_type callback)
+{
+    if (!callback || ucallback)
+        return; /* Is busy */
+
+    unsigned long status = disable_interrupt_save(IRQ_FIQ_STATUS);
+
+    ucallback = callback;
+
+    for (int i = 0; i < 1; i++)
+    {
+        unsigned long utime = GPTCNT;
+        unsigned long time = utime + usecs + 1;
+
+        GPTOCR1 = time;
+        GPTSR = GPTSR_OF1;
+        GPTIR |= GPTIR_OF1IE;
+
+        if (TIME_BEFORE(GPTCNT, time))
+            break; /* Didn't miss it */
+    }
+
+    restore_interrupt(status);
+}
+
+void uevent_cancel(void)
+{
+    unsigned long status = disable_interrupt_save(IRQ_FIQ_STATUS);
+
+    if (ucallback)
+        cancel_uevent();
+
+    restore_interrupt(status);
+}
+
+
+/** GPT timer routines - basis for udelay/uevent **/
 
 /* Start the general-purpose timer (1MHz) */
 void gpt_start(void)
@@ -102,13 +157,20 @@ void gpt_start(void)
      */
     GPTCR = GPTCR_FRR | GPTCR_WAITEN | GPTCR_CLKSRC_IPG_CLK;
     GPTPR = ipg_mhz - 1;
+    GPTSR = GPTSR_OF1;
     GPTCR |= GPTCR_EN;
+
+    avic_enable_int(INT_GPT, INT_TYPE_IRQ, INT_PRIO_GPT, GPT_HANDLER);
 }
 
 /* Stop the general-purpose timer */
 void gpt_stop(void)
 {
+    unsigned long status = disable_interrupt_save(IRQ_FIQ_STATUS);
+    avic_disable_int(INT_GPT);
+    cancel_uevent();
     GPTCR &= ~GPTCR_EN;
+    restore_interrupt(status);
 }
 
 int system_memory_guard(int newmode)
@@ -258,7 +320,7 @@ void dumpregs(void)
                   "mov %3,r12":
                   "=r"(regs.r8),"=r"(regs.r9),
                   "=r"(regs.r10),"=r"(regs.r11):);
-  
+
     asm volatile ("mov %0,r12\n\t"
                    "mov %1,sp\n\t"
                    "mov %2,lr\n\t"
@@ -280,7 +342,7 @@ void dumpregs(void)
     DEBUGF("R8=0x%x\tR9=0x%x\tR10=0x%x\tR11=0x%x\n",regs.r8,regs.r9,regs.r10,regs.r11);
     DEBUGF("R12=0x%x\tSP=0x%x\tLR=0x%x\tPC=0x%x\n",regs.r12,regs.sp,regs.lr,regs.pc);
     //DEBUGF("CPSR=0x%x\t\n",regs.cpsr);
-    
+
  }
 
 #ifdef HAVE_ADJUSTABLE_CPU_FREQ

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

@@ -44,6 +44,11 @@ static inline unsigned long usec_timer(void)
     return GPTCNT;
 }
 
+/* Fire an event usecs microseconds from now */
+typedef void (* uevent_cb_type)(void);
+void uevent(unsigned long usecs, uevent_cb_type callback);
+void uevent_cancel(void);
+
 void watchdog_init(unsigned int half_seconds);
 void watchdog_service(void);
 
@@ -58,9 +63,6 @@ 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 {