From dc32a5b14ccad55ce1f1848a16d5605b9019ae87 Mon Sep 17 00:00:00 2001
From: Rafaël Carré <rafael.carre@gmail.com>
Date: Tue, 1 Jun 2010 09:39:08 +0000
Subject: as3525 PCM: implement locking like done for the gigabeats in r26341

this removes workaround for spurious interrupts added in r26316

side effect: make keyclicks work correctly when used intensively (with
the scrollwheel for example), the clicks should be inserted fast enough
for the PCM fifo to not become empty.

PL190 can cause spurious interrupts if an interrupt is triggered by a
peripheral shortly before the interrupt for this peripheral is cleared
from VIC registers.

As an effect we should only write in VIC_INT_EN_CLEAR after having
disabled the source of the interrupt in the peripheral.

references on PL190 spurious interrupts:
- http://www.embeddedrelated.com/groups/lpc2000/show/14599.php
- http://water.cse.unsw.edu.au/esdk/lpc2/spurious-irq.html

git-svn-id: svn://svn.rockbox.org/rockbox/trunk@26444 a1c6a512-1295-4272-9138-f99709370657
---
 firmware/target/arm/as3525/pcm-as3525.c | 72 ++++++++++++++++++++++++++-------
 1 file changed, 57 insertions(+), 15 deletions(-)

diff --git a/firmware/target/arm/as3525/pcm-as3525.c b/firmware/target/arm/as3525/pcm-as3525.c
index 5a403bad83..9f31d623fe 100644
--- a/firmware/target/arm/as3525/pcm-as3525.c
+++ b/firmware/target/arm/as3525/pcm-as3525.c
@@ -39,21 +39,28 @@ static unsigned char *dma_start_addr;
 static size_t      dma_size;   /* in 4*32 bits */
 static void dma_callback(void);
 static int locked = 0;
-
-static int play_irq_state;
+static bool is_playing = false;
+static bool play_callback_pending = false;
 
 /* Mask the DMA interrupt */
 void pcm_play_lock(void)
 {
-    if(++locked == 1)
-        play_irq_state = disable_irq_save();
+    ++locked;
 }
 
 /* Unmask the DMA interrupt if enabled */
 void pcm_play_unlock(void)
 {
-    if(--locked == 0)
-        restore_irq(play_irq_state);
+    if(--locked == 0 && is_playing)
+    {
+        int old = disable_irq_save();
+        if(play_callback_pending)
+        {
+            play_callback_pending = false;
+            dma_callback();
+        }
+        restore_irq(old);
+    }
 }
 
 static void play_start_pcm(void)
@@ -74,6 +81,12 @@ static void play_start_pcm(void)
 
 static void dma_callback(void)
 {
+    if(locked)
+    {
+        play_callback_pending = is_playing;
+        return;
+    }
+
     if(!dma_size)
     {
         pcm_play_get_more_callback((void **)&dma_start_addr, &dma_size);
@@ -95,11 +108,14 @@ void pcm_play_dma_start(const void *addr, size_t size)
 
     dma_retain();
 
+    is_playing = true;
+
     play_start_pcm();
 }
 
 void pcm_play_dma_stop(void)
 {
+    is_playing = false;
     dma_disable_channel(1);
     dma_size = 0;
 
@@ -111,6 +127,8 @@ void pcm_play_dma_stop(void)
 
 void pcm_play_dma_pause(bool pause)
 {
+    is_playing = !pause;
+
     if(pause)
         dma_disable_channel(1);
     else
@@ -192,6 +210,8 @@ void * pcm_dma_addr(void *addr)
 #ifdef HAVE_RECORDING
 
 static int rec_locked = 0;
+static bool is_recording = false;
+static bool rec_callback_pending = false;
 static unsigned char *rec_dma_start_addr;
 static size_t rec_dma_size, rec_dma_transfer_size;
 static void rec_dma_callback(void);
@@ -200,19 +220,25 @@ static void rec_dma_callback(void);
 static int16_t *mono_samples;
 #endif
 
-static int rec_irq_state;
 
 void pcm_rec_lock(void)
 {
-    if(++rec_locked == 1)
-        rec_irq_state = disable_irq_save();
+    ++rec_locked;
 }
 
 
 void pcm_rec_unlock(void)
 {
-    if(--rec_locked == 0)
-        restore_irq(rec_irq_state);
+    if(--rec_locked == 0 && is_recording)
+    {
+        int old = disable_irq_save();
+        if(rec_callback_pending)
+        {
+            rec_callback_pending = false;
+            rec_dma_callback();
+        }
+        restore_irq(old);
+    }
 }
 
 
@@ -268,11 +294,24 @@ static inline void mono2stereo(int16_t *end)
 
 static void rec_dma_callback(void)
 {
-    rec_dma_size -= rec_dma_transfer_size;
-    rec_dma_start_addr += rec_dma_transfer_size;
+    if(rec_dma_transfer_size)
+    {
+        rec_dma_size -= rec_dma_transfer_size;
+        rec_dma_start_addr += rec_dma_transfer_size;
+
+        /* don't act like we just transferred data when we are called from
+         * pcm_rec_unlock() */
+        rec_dma_transfer_size = 0;
 
-    /* the 2nd channel is silent when recording microphone on as3525v1 */
-    mono2stereo(AS3525_UNCACHED_ADDR((int16_t*)rec_dma_start_addr));
+        /* the 2nd channel is silent when recording microphone on as3525v1 */
+        mono2stereo(AS3525_UNCACHED_ADDR((int16_t*)rec_dma_start_addr));
+
+        if(locked)
+        {
+            rec_callback_pending = is_recording;
+            return;
+        }
+    }
 
     if(!rec_dma_size)
     {
@@ -293,6 +332,7 @@ static void rec_dma_callback(void)
 
 void pcm_rec_dma_stop(void)
 {
+    is_recording = false;
     dma_disable_channel(1);
     dma_release();
     rec_dma_size = 0;
@@ -320,6 +360,8 @@ void pcm_rec_dma_start(void *addr, size_t size)
 
     I2SIN_CONTROL |= (1<<11)|(1<<5); /* enable dma, 14bits samples */
 
+    is_recording = true;
+
     rec_dma_start();
 }
 
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