ALSA: AACI: make fifo variables more explanitory

Improve commenting and change fifo variable names to reflect their
meanings.

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

2 files changed, 26 insertions, 20 deletions

diff --git a/sound/arm/aaci.c b/sound/arm/aaci.c
index 393ce08b0e11..a148e275c80f 100644
--- a/sound/arm/aaci.c
+++ b/sound/arm/aaci.c
@@ -219,7 +219,7 @@ static void aaci_fifo_irq(struct aaci *aaci, int channel, u32 mask)
 
                 ptr = aacirun->ptr;
                 do {
-                        unsigned int len = aacirun->fifosz;
+                        unsigned int len = aacirun->fifo_bytes;
                         u32 val;
 
                         if (aacirun->bytes <= 0) {
@@ -279,7 +279,7 @@ static void aaci_fifo_irq(struct aaci *aaci, int channel, u32 mask)
 
                 ptr = aacirun->ptr;
                 do {
-                        unsigned int len = aacirun->fifosz;
+                        unsigned int len = aacirun->fifo_bytes;
                         u32 val;
 
                         if (aacirun->bytes <= 0) {
@@ -430,13 +430,11 @@ static int aaci_pcm_open(struct snd_pcm_substream *substream)
         }
 
         /*
-         * FIXME: ALSA specifies fifo_size in bytes.  If we're in normal
-         * mode, each 32-bit word contains one sample.  If we're in
-         * compact mode, each 32-bit word contains two samples, effectively
-         * halving the FIFO size.  However, we don't know for sure which
-         * we'll be using at this point.  We set this to the lower limit.
+         * ALSA wants the byte-size of the FIFOs.  As we only support
+         * 16-bit samples, this is twice the FIFO depth irrespective
+         * of whether it's in compact mode or not.
          */
-        runtime->hw.fifo_size = aaci->fifosize * 2;
+        runtime->hw.fifo_size = aaci->fifo_depth * 2;
 
         mutex_lock(&aaci->irq_lock);
         if (!aaci->users++) {
@@ -529,10 +527,13 @@ static int aaci_pcm_hw_params(struct snd_pcm_substream *substream,
                 aacirun->pcm_open = err == 0;
                 aacirun->cr = CR_FEN | CR_COMPACT | CR_SZ16;
                 aacirun->cr |= channels_to_slotmask[channels + dbl * 2];
-                aacirun->fifosz = aaci->fifosize * 4;
 
-                if (aacirun->cr & CR_COMPACT)
-                        aacirun->fifosz >>= 1;
+                /*
+                 * fifo_bytes is the number of bytes we transfer to/from
+                 * the FIFO, including padding.  So that's x4.  As we're
+                 * in compact mode, the FIFO is half the size.
+                 */
+                aacirun->fifo_bytes = aaci->fifo_depth * 4 / 2;
         }
 
         return err;
@@ -948,6 +949,10 @@ static unsigned int __devinit aaci_size_fifo(struct aaci *aaci)
         struct aaci_runtime *aacirun = &aaci->playback;
         int i;
 
+        /*
+         * Enable the channel, but don't assign it to any slots, so
+         * it won't empty onto the AC'97 link.
+         */
         writel(CR_FEN | CR_SZ16 | CR_EN, aacirun->base + AACI_TXCR);
 
         for (i = 0; !(readl(aacirun->base + AACI_SR) & SR_TXFF) && i < 4096; i++)
@@ -964,7 +969,7 @@ static unsigned int __devinit aaci_size_fifo(struct aaci *aaci)
         writel(aaci->maincr, aaci->base + AACI_MAINCR);
 
         /*
-         * If we hit 4096, we failed.  Go back to the specified
+         * If we hit 4096 entries, we failed.  Go back to the specified
          * fifo depth.
          */
         if (i == 4096)
@@ -1029,11 +1034,12 @@ static int __devinit aaci_probe(struct amba_device *dev, struct amba_id *id)
 
         /*
          * Size the FIFOs (must be multiple of 16).
+         * This is the number of entries in the FIFO.
          */
-        aaci->fifosize = aaci_size_fifo(aaci);
-        if (aaci->fifosize & 15) {
-                printk(KERN_WARNING "AACI: fifosize = %d not supported\n",
-                       aaci->fifosize);
+        aaci->fifo_depth = aaci_size_fifo(aaci);
+        if (aaci->fifo_depth & 15) {
+                printk(KERN_WARNING "AACI: FIFO depth %d not supported\n",
+                       aaci->fifo_depth);
                 ret = -ENODEV;
                 goto out;
         }
@@ -1046,8 +1052,8 @@ static int __devinit aaci_probe(struct amba_device *dev, struct amba_id *id)
 
         ret = snd_card_register(aaci->card);
         if (ret == 0) {
-                dev_info(&dev->dev, "%s, fifo %d\n", aaci->card->longname,
-                         aaci->fifosize);
+                dev_info(&dev->dev, "%s\n", aaci->card->longname);
+                dev_info(&dev->dev, "FIFO %u entries\n", aaci->fifo_depth);
                 amba_set_drvdata(dev, aaci->card);
                 return ret;
         }
diff --git a/sound/arm/aaci.h b/sound/arm/aaci.h
index 198750d6871d..5791bd5bd2ab 100644
--- a/sound/arm/aaci.h
+++ b/sound/arm/aaci.h
@@ -219,14 +219,14 @@ struct aaci_runtime {
         void                    *end;
         void                    *ptr;
         int                     bytes;
-        unsigned int            fifosz;
+        unsigned int            fifo_bytes;
 };
 
 struct aaci {
         struct amba_device      *dev;
         struct snd_card         *card;
         void                    __iomem *base;
-        unsigned int            fifosize;
+        unsigned int            fifo_depth;
         unsigned int            users;
         struct mutex            irq_lock;