Back to byte-aligned bitswapping

git-svn-id: svn://svn.rockbox.org/rockbox/trunk@2519 a1c6a512-1295-4272-9138-f99709370657

firmware/bitswap.S

@@ -25,36 +25,27 @@
 /* Registers used:
  *
  * r0   Temporary (required by some instructions)
- * r1	Low byte
+ * r1   Flip table
- * r2	High byte
+ * r4   Argument:  Data pointer
- * r3	Result after flip
+ * r5   Argument:  Length (in bytes)
- * r4	Data
- * r5	Length
- * r6	Current (position in Data)
- * r7	Flip table
  */
 
+/* TODO: Optimize for DRAM burst operation by reading and writing in chunks
+   We do not want to optimize by reading/writing words, because the data
+   pointer may be odd */
+ 
 _bitswap:
-	mov.l	.fliptable,r7
+    mov.l   .fliptable,r1
-	mov	r4,r6
+    add r4,r5             /* Calculate end of buffer */
-	add	r5,r6				/* goto end of buffer */
-	add	r5,r6				/* (direction IS important) */
     bra .init
 .loop:
-	mov.w	@r4,r1				/* data to flip */
+    mov.b   @r4,r0        /* Data to flip */
-	swap.b	r1,r2
+    extu.b  r0,r0         /* Zero extend */
-	extu.b	r2,r0				/* high byte */
+    mov.b   @(r0,r1),r0   /* Look up in the flip table */
-	mov.b	@(r0,r7),r2
+    mov.b   r0,@r4        /* Store result */
-	extu.b	r2,r0				/* remove any sign extend */
+    add #1,r4
-	swap.b	r0,r3				/* put high byte in result */
-	extu.b	r1,r0				/* low byte */
-	mov.b	@(r0,r7),r1
-	extu.b	r1,r0				/* remove any sign extend */
-	or	r0,r3				/* put low byte in result */
-	mov.w	r3,@r4				/* store result */
-	add	#2,r4
 .init:
-	cmp/gt	r4,r6				/* while (data < start+length*2) */
+    cmp/gt  r4,r5         /* while (dataptr < start+length) */
     bt  .loop
     rts
 

firmware/mpeg.c

@@ -35,7 +35,7 @@
 #include "file.h"
 #endif
 
-extern void bitswap(unsigned short *data, int length);
+extern void bitswap(unsigned char *data, int length);
 
 #define MPEG_CHUNKSIZE  0x180000
 #define MPEG_SWAP_CHUNKSIZE  0x8000
@@ -465,9 +465,30 @@ static void mas_poll_start(int interval_in_ms)
     TSR1 &= ~0x02;
     TIER1 = 0xf9; /* Enable GRA match interrupt */
 
-    TSTR |= 0x02; /* Start timer 2 */
+    TSTR |= 0x02; /* Start timer 1 */
 }
 
+#ifdef DEBUG
+static void dbg_timer_start(void)
+{
+    /* We are using timer 2 */
+    
+    TSTR &= ~0x04; /* Stop the timer */
+    TSNC &= ~0x04; /* No synchronization */
+    TMDR &= ~0x44; /* Operate normally */
+
+    TCNT1 = 0;   /* Start counting at 0 */
+    TCR1 = 0x03; /* Sysclock/8 */
+
+    TSTR |= 0x04; /* Start timer 2 */
+}
+
+static int dbg_cnt2us(unsigned int cnt)
+{
+    return (cnt * 10000) / (FREQ/800);
+}
+#endif
+
 static int get_unplayed_space(void)
 {
     int space = mp3buf_write - mp3buf_read;
@@ -704,7 +725,7 @@ static int new_file(int steps)
             }
             else
             {
-                /* skip past id3v2 tag (to an even byte) */
+                /* skip past id3v2 tag */
                 lseek(mpeg_file, 
                       id3tags[new_tag_idx]->id3.id3v2len,
                       SEEK_SET);
@@ -827,9 +848,9 @@ static void mpeg_thread(void)
                     set_elapsed(id3);
                 }
                 else {
-                    /* skip past id3v2 tag (to an even byte) */
+                    /* skip past id3v2 tag */
                     lseek(mpeg_file, 
-                          id3tags[tag_read_idx]->id3.id3v2len & ~1, 
+                          id3tags[tag_read_idx]->id3.id3v2len, 
                           SEEK_SET);
 
                 }
@@ -1046,8 +1067,6 @@ static void mpeg_thread(void)
                     newpos = id3->id3v2len;
                 }
 
-                newpos = newpos & ~1;
-
                 if (mpeg_file >= 0)
                     curpos = lseek(mpeg_file, 0, SEEK_CUR);
                 else
@@ -1196,8 +1215,7 @@ static void mpeg_thread(void)
                 
                 DEBUGF("B %x\n", amount_to_swap);
                 t1 = current_tick;
-                bitswap((unsigned short *)(mp3buf + mp3buf_swapwrite),
+                bitswap(mp3buf + mp3buf_swapwrite, amount_to_swap);
-                        (amount_to_swap+1)/2);
                 t2 = current_tick;
                 DEBUGF("time: %d\n", t2 - t1);
 
@@ -2054,6 +2072,10 @@ void mpeg_init(int volume, int bass, int treble, int balance, int loudness, int
 
     memset(id3tags, sizeof(id3tags), 0);
     memset(_id3tags, sizeof(id3tags), 0);
+
+#ifdef DEBUG
+    dbg_timer_start();
+#endif
 }
 
 /* -----------------------------------------------------------------