[ALSA] maestro3.c: fix BUG, optimization

- fix brown-paper-bag locking bug (lock() / return / unlock())
- improve central function snd_m3_update_ptr()
  (avoid expensive integer divisions)
- add cpu_relax() to busy-wait I/O loop as recommended
  (does this require special macro support in ALSA for older kernels??)
- constify several structs
- spelling updates

Signed-off-by: Andreas Mohr <andi@lisas.de>
Signed-off-by: Takashi Iwai <tiwai@suse.de>

1 files changed, 37 insertions, 20 deletions

diff --git a/sound/pci/maestro3.c b/sound/pci/maestro3.c
index 44393e190929..9c90d901e6b9 100644
--- a/sound/pci/maestro3.c
+++ b/sound/pci/maestro3.c
@@ -831,8 +831,8 @@ struct snd_m3 {
         struct snd_pcm *pcm;
 
         struct pci_dev *pci;
-        struct m3_quirk *quirk;
-        struct m3_hv_quirk *hv_quirk;
+        const struct m3_quirk *quirk;
+        const struct m3_hv_quirk *hv_quirk;
 
         int dacs_active;
         int timer_users;
@@ -892,7 +892,7 @@ static struct pci_device_id snd_m3_ids[] = {
 
 MODULE_DEVICE_TABLE(pci, snd_m3_ids);
 
-static struct m3_quirk m3_quirk_list[] = {
+static const struct m3_quirk m3_quirk_list[] = {
         /* panasonic CF-28 "toughbook" */
         {
                 .name = "Panasonic CF-28",
@@ -950,7 +950,7 @@ static struct m3_quirk m3_quirk_list[] = {
 };
 
 /* These values came from the Windows driver. */
-static struct m3_hv_quirk m3_hv_quirk_list[] = {
+static const struct m3_hv_quirk m3_hv_quirk_list[] = {
         /* Allegro chips */
         { 0x125D, 0x1988, 0x0E11, 0x002E, HV_CTRL_ENABLE | HV_BUTTON_FROM_GD, 0 },
         { 0x125D, 0x1988, 0x0E11, 0x0094, HV_CTRL_ENABLE | HV_BUTTON_FROM_GD, 0 },
@@ -1361,7 +1361,7 @@ static void snd_m3_pcm_setup2(struct snd_m3 *chip, struct m3_dma *s,
 }
 
 
-static struct play_vals {
+static const struct play_vals {
         u16 addr, val;
 } pv[] = {
         {CDATA_LEFT_VOLUME, ARB_VOLUME},
@@ -1428,7 +1428,7 @@ snd_m3_playback_setup(struct snd_m3 *chip, struct m3_dma *s,
 /*
  *    Native record driver 
  */
-static struct rec_vals {
+static const struct rec_vals {
         u16 addr, val;
 } rv[] = {
         {CDATA_LEFT_VOLUME, ARB_VOLUME},
@@ -1598,12 +1598,26 @@ static void snd_m3_update_ptr(struct snd_m3 *chip, struct m3_dma *s)
         if (! s->running)
                 return;
 
-        hwptr = snd_m3_get_pointer(chip, s, subs) % s->dma_size;
-        diff = (s->dma_size + hwptr - s->hwptr) % s->dma_size;
+        hwptr = snd_m3_get_pointer(chip, s, subs);
+
+        /* try to avoid expensive modulo divisions */
+        if (hwptr >= s->dma_size)
+                hwptr %= s->dma_size;
+
+        diff = s->dma_size + hwptr - s->hwptr;
+        if (diff >= s->dma_size)
+                diff %= s->dma_size;
+
         s->hwptr = hwptr;
         s->count += diff;
+
         if (s->count >= (signed)s->period_size) {
-                s->count %= s->period_size;
+
+                if (s->count < 2 * (signed)s->period_size)
+                        s->count -= (signed)s->period_size;
+                else
+                        s->count %= s->period_size;
+
                 spin_unlock(&chip->reg_lock);
                 snd_pcm_period_elapsed(subs);
                 spin_lock(&chip->reg_lock);
@@ -1942,6 +1956,7 @@ static int snd_m3_ac97_wait(struct snd_m3 *chip)
         do {
                 if (! (snd_m3_inb(chip, 0x30) & 1))
                         return 0;
+                cpu_relax();
         } while (i-- > 0);
 
         snd_printk(KERN_ERR "ac97 serial bus busy\n");
@@ -1953,16 +1968,18 @@ snd_m3_ac97_read(struct snd_ac97 *ac97, unsigned short reg)
 {
         struct snd_m3 *chip = ac97->private_data;
         unsigned long flags;
-        unsigned short data;
+        unsigned short data = 0xffff;
 
         if (snd_m3_ac97_wait(chip))
-                return 0xffff;
+                goto fail;
         spin_lock_irqsave(&chip->ac97_lock, flags);
         snd_m3_outb(chip, 0x80 | (reg & 0x7f), CODEC_COMMAND);
         if (snd_m3_ac97_wait(chip))
-                return 0xffff;
+                goto fail_unlock;
         data = snd_m3_inw(chip, CODEC_DATA);
+fail_unlock:
         spin_unlock_irqrestore(&chip->ac97_lock, flags);
+fail:
         return data;
 }
 
@@ -2121,7 +2138,7 @@ static int __devinit snd_m3_mixer(struct snd_m3 *chip)
  * DSP Code images
  */
 
-static u16 assp_kernel_image[] __devinitdata = {
+static const u16 assp_kernel_image[] __devinitdata = {
     0x7980, 0x0030, 0x7980, 0x03B4, 0x7980, 0x03B4, 0x7980, 0x00FB, 0x7980, 0x00DD, 0x7980, 0x03B4, 
     0x7980, 0x0332, 0x7980, 0x0287, 0x7980, 0x03B4, 0x7980, 0x03B4, 0x7980, 0x03B4, 0x7980, 0x03B4, 
     0x7980, 0x031A, 0x7980, 0x03B4, 0x7980, 0x022F, 0x7980, 0x03B4, 0x7980, 0x03B4, 0x7980, 0x03B4, 
@@ -2208,7 +2225,7 @@ static u16 assp_kernel_image[] __devinitdata = {
  * Mini sample rate converter code image
  * that is to be loaded at 0x400 on the DSP.
  */
-static u16 assp_minisrc_image[] __devinitdata = {
+static const u16 assp_minisrc_image[] __devinitdata = {
 
     0xBF80, 0x101E, 0x906E, 0x006E, 0x8B88, 0x6980, 0xEF88, 0x906F, 0x0D6F, 0x6900, 0xEB08, 0x0412, 
     0xBC20, 0x696E, 0xB801, 0x906E, 0x7980, 0x0403, 0xB90E, 0x8807, 0xBE43, 0xBF01, 0xBE47, 0xBE41, 
@@ -2251,7 +2268,7 @@ static u16 assp_minisrc_image[] __devinitdata = {
  */
 
 #define MINISRC_LPF_LEN 10
-static u16 minisrc_lpf[MINISRC_LPF_LEN] __devinitdata = {
+static const u16 minisrc_lpf[MINISRC_LPF_LEN] __devinitdata = {
         0X0743, 0X1104, 0X0A4C, 0XF88D, 0X242C,
         0X1023, 0X1AA9, 0X0B60, 0XEFDD, 0X186F
 };
@@ -2358,7 +2375,7 @@ static int __devinit snd_m3_assp_client_init(struct snd_m3 *chip, struct m3_dma
          */
 
         /*
-         * align instance address to 256 bytes so that it's
+         * align instance address to 256 bytes so that its
          * shifted list address is aligned.
          * list address = (mem address >> 1) >> 7;
          */
@@ -2647,8 +2664,8 @@ snd_m3_create(struct snd_card *card, struct pci_dev *pci,
 {
         struct snd_m3 *chip;
         int i, err;
-        struct m3_quirk *quirk;
-        struct m3_hv_quirk *hv_quirk;
+        const struct m3_quirk *quirk;
+        const struct m3_hv_quirk *hv_quirk;
         static struct snd_device_ops ops = {
                 .dev_free =     snd_m3_dev_free,
         };
@@ -2843,12 +2860,12 @@ snd_m3_probe(struct pci_dev *pci, const struct pci_device_id *pci_id)
         }
 
 #if 0 /* TODO: not supported yet */
-        /* TODO enable midi irq and i/o */
+        /* TODO enable MIDI IRQ and I/O */
         err = snd_mpu401_uart_new(chip->card, 0, MPU401_HW_MPU401,
                                   chip->iobase + MPU401_DATA_PORT, 1,
                                   chip->irq, 0, &chip->rmidi);
         if (err < 0)
-                printk(KERN_WARNING "maestro3: no midi support.\n");
+                printk(KERN_WARNING "maestro3: no MIDI support.\n");
 #endif
 
         pci_set_drvdata(pci, card);