[ALSA] Reduce interrupt latency in sound/pci/via82xx.c
Modules: VIA82xx driver The change only affects the via823x kind of chips. Here the via8233_pcm_pointer_hw() function (named snd_via8233_pcm_pointer() before) needed to loop until a non zero position is red from the chip. Measurements have shown that more than 200 loops are typically needed on an Athlon64. As io-reads cost many cycles, those loops sum up huge. via8233_pcm_pointer_hw() runs either in interrupt or with interrupts disabled. So it introduces significant interrupt latency. The patch introduces a calculated position value hwptr_done, that is updated by the interrupt routine when a period is completed. It is only used, if the 823x chip returns a zero position, which can't be interpreted reliably. Further optimisation is applied on the 8233 chip's interrupt routine: Only the SGD_SHADOW is read, as it contains all infos needed. We ommit ~5 more register reads that way. Signed-off-by: Karsten Wiese <annabellesgarden@yahoo.de> Signed-off-by: Takashi Iwai <tiwai@suse.de>
This commit is contained in:
Karsten Wiese
Jaroslav Kysela
parent
f0597a416d
commit
4f550df58f
@ -41,6 +41,9 @@
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* device for applications.
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* - clean up the code, separate low-level initialization
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* routines for each chipset.
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*
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* Sep. 26, 2005 Karsten Wiese <annabellesgarden@yahoo.de>
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* - Optimize position calculation for the 823x chips.
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*/
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#include <sound/driver.h>
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@ -131,6 +134,7 @@ module_param(enable, int, 0444);
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/* common offsets */
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#define VIA_REG_OFFSET_STATUS 0x00 /* byte - channel status */
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#define VIA_REG_STAT_ACTIVE 0x80 /* RO */
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#define VIA8233_SHADOW_STAT_ACTIVE 0x08 /* RO */
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#define VIA_REG_STAT_PAUSED 0x40 /* RO */
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#define VIA_REG_STAT_TRIGGER_QUEUED 0x08 /* RO */
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#define VIA_REG_STAT_STOPPED 0x04 /* RWC */
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@ -329,6 +333,9 @@ struct via_dev {
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unsigned int fragsize;
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unsigned int bufsize;
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unsigned int bufsize2;
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int hwptr_done; /* processed frame position in the buffer */
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int in_interrupt;
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int shadow_shift;
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};
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@ -395,8 +402,10 @@ struct _snd_via82xx {
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};
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static struct pci_device_id snd_via82xx_ids[] = {
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{ 0x1106, 0x3058, PCI_ANY_ID, PCI_ANY_ID, 0, 0, TYPE_CARD_VIA686, }, /* 686A */
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{ 0x1106, 0x3059, PCI_ANY_ID, PCI_ANY_ID, 0, 0, TYPE_CARD_VIA8233, }, /* VT8233 */
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/* 0x1106, 0x3058 */
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{ PCI_VENDOR_ID_VIA, PCI_DEVICE_ID_VIA_82C686_5, PCI_ANY_ID, PCI_ANY_ID, 0, 0, TYPE_CARD_VIA686, }, /* 686A */
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/* 0x1106, 0x3059 */
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{ PCI_VENDOR_ID_VIA, PCI_DEVICE_ID_VIA_8233_5, PCI_ANY_ID, PCI_ANY_ID, 0, 0, TYPE_CARD_VIA8233, }, /* VT8233 */
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{ 0, }
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};
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@ -550,7 +559,7 @@ static void snd_via82xx_codec_write(ac97_t *ac97,
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{
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via82xx_t *chip = ac97->private_data;
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unsigned int xval;
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xval = !ac97->num ? VIA_REG_AC97_CODEC_ID_PRIMARY : VIA_REG_AC97_CODEC_ID_SECONDARY;
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xval <<= VIA_REG_AC97_CODEC_ID_SHIFT;
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xval |= reg << VIA_REG_AC97_CMD_SHIFT;
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@ -598,14 +607,15 @@ static void snd_via82xx_channel_reset(via82xx_t *chip, viadev_t *viadev)
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outb(0x00, VIADEV_REG(viadev, OFFSET_TYPE)); /* for via686 */
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// outl(0, VIADEV_REG(viadev, OFFSET_CURR_PTR));
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viadev->lastpos = 0;
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viadev->hwptr_done = 0;
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}
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/*
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* Interrupt handler
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* Used for 686 and 8233A
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*/
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static irqreturn_t snd_via82xx_interrupt(int irq, void *dev_id, struct pt_regs *regs)
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static irqreturn_t snd_via686_interrupt(int irq, void *dev_id, struct pt_regs *regs)
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{
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via82xx_t *chip = dev_id;
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unsigned int status;
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@ -624,13 +634,23 @@ static irqreturn_t snd_via82xx_interrupt(int irq, void *dev_id, struct pt_regs *
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for (i = 0; i < chip->num_devs; i++) {
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viadev_t *viadev = &chip->devs[i];
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unsigned char c_status = inb(VIADEV_REG(viadev, OFFSET_STATUS));
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c_status &= (VIA_REG_STAT_EOL|VIA_REG_STAT_FLAG|VIA_REG_STAT_STOPPED);
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if (! c_status)
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if (! (c_status & (VIA_REG_STAT_EOL|VIA_REG_STAT_FLAG|VIA_REG_STAT_STOPPED)))
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continue;
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if (viadev->substream && viadev->running) {
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/*
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* Update hwptr_done based on 'period elapsed'
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* interrupts. We'll use it, when the chip returns 0
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* for OFFSET_CURR_COUNT.
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*/
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if (c_status & VIA_REG_STAT_EOL)
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viadev->hwptr_done = 0;
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else
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viadev->hwptr_done += viadev->fragsize;
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viadev->in_interrupt = c_status;
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spin_unlock(&chip->reg_lock);
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snd_pcm_period_elapsed(viadev->substream);
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spin_lock(&chip->reg_lock);
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viadev->in_interrupt = 0;
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}
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outb(c_status, VIADEV_REG(viadev, OFFSET_STATUS)); /* ack */
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}
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@ -638,6 +658,60 @@ static irqreturn_t snd_via82xx_interrupt(int irq, void *dev_id, struct pt_regs *
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return IRQ_HANDLED;
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}
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/*
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* Interrupt handler
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*/
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static irqreturn_t snd_via8233_interrupt(int irq, void *dev_id, struct pt_regs *regs)
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{
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via82xx_t *chip = dev_id;
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unsigned int status;
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unsigned int i;
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int irqreturn = 0;
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/* check status for each stream */
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spin_lock(&chip->reg_lock);
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status = inl(VIAREG(chip, SGD_SHADOW));
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for (i = 0; i < chip->num_devs; i++) {
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viadev_t *viadev = &chip->devs[i];
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snd_pcm_substream_t *substream;
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unsigned char c_status, shadow_status;
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shadow_status = (status >> viadev->shadow_shift) &
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(VIA8233_SHADOW_STAT_ACTIVE|VIA_REG_STAT_EOL|
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VIA_REG_STAT_FLAG);
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c_status = shadow_status & (VIA_REG_STAT_EOL|VIA_REG_STAT_FLAG);
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if (!c_status)
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continue;
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substream = viadev->substream;
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if (substream && viadev->running) {
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/*
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* Update hwptr_done based on 'period elapsed'
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* interrupts. We'll use it, when the chip returns 0
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* for OFFSET_CURR_COUNT.
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*/
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if (c_status & VIA_REG_STAT_EOL)
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viadev->hwptr_done = 0;
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else
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viadev->hwptr_done += viadev->fragsize;
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viadev->in_interrupt = c_status;
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if (shadow_status & VIA8233_SHADOW_STAT_ACTIVE)
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viadev->in_interrupt |= VIA_REG_STAT_ACTIVE;
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spin_unlock(&chip->reg_lock);
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snd_pcm_period_elapsed(substream);
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spin_lock(&chip->reg_lock);
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viadev->in_interrupt = 0;
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}
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outb(c_status, VIADEV_REG(viadev, OFFSET_STATUS)); /* ack */
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irqreturn = 1;
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}
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spin_unlock(&chip->reg_lock);
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return IRQ_RETVAL(irqreturn);
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}
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/*
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* PCM callbacks
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*/
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@ -701,6 +775,8 @@ static inline unsigned int calc_linear_pos(viadev_t *viadev, unsigned int idx, u
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size = viadev->idx_table[idx].size;
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base = viadev->idx_table[idx].offset;
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res = base + size - count;
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if (res >= viadev->bufsize)
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res -= viadev->bufsize;
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/* check the validity of the calculated position */
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if (size < count) {
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@ -730,9 +806,6 @@ static inline unsigned int calc_linear_pos(viadev_t *viadev, unsigned int idx, u
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}
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}
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}
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viadev->lastpos = res; /* remember the last position */
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if (res >= viadev->bufsize)
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res -= viadev->bufsize;
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return res;
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}
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@ -760,6 +833,7 @@ static snd_pcm_uframes_t snd_via686_pcm_pointer(snd_pcm_substream_t *substream)
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else /* CURR_PTR holds the address + 8 */
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idx = ((ptr - (unsigned int)viadev->table.addr) / 8 - 1) % viadev->tbl_entries;
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res = calc_linear_pos(viadev, idx, count);
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viadev->lastpos = res; /* remember the last position */
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spin_unlock(&chip->reg_lock);
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return bytes_to_frames(substream->runtime, res);
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@ -773,30 +847,44 @@ static snd_pcm_uframes_t snd_via8233_pcm_pointer(snd_pcm_substream_t *substream)
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via82xx_t *chip = snd_pcm_substream_chip(substream);
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viadev_t *viadev = (viadev_t *)substream->runtime->private_data;
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unsigned int idx, count, res;
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int timeout = 5000;
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int status;
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snd_assert(viadev->tbl_entries, return 0);
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if (!(inb(VIADEV_REG(viadev, OFFSET_STATUS)) & VIA_REG_STAT_ACTIVE))
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return 0;
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spin_lock(&chip->reg_lock);
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do {
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count = inl(VIADEV_REG(viadev, OFFSET_CURR_COUNT));
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/* some mobos read 0 count */
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if ((count & 0xffffff) || ! viadev->running)
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break;
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} while (--timeout);
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if (! timeout)
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snd_printd(KERN_ERR "zero position is read\n");
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idx = count >> 24;
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if (idx >= viadev->tbl_entries) {
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#ifdef POINTER_DEBUG
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printk("fail: invalid idx = %i/%i\n", idx, viadev->tbl_entries);
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#endif
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res = viadev->lastpos;
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} else {
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count &= 0xffffff;
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res = calc_linear_pos(viadev, idx, count);
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count = inl(VIADEV_REG(viadev, OFFSET_CURR_COUNT));
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status = viadev->in_interrupt;
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if (!status)
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status = inb(VIADEV_REG(viadev, OFFSET_STATUS));
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if (!(status & VIA_REG_STAT_ACTIVE)) {
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res = 0;
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goto unlock;
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}
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if (count & 0xffffff) {
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idx = count >> 24;
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if (idx >= viadev->tbl_entries) {
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#ifdef POINTER_DEBUG
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printk("fail: invalid idx = %i/%i\n", idx, viadev->tbl_entries);
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#endif
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res = viadev->lastpos;
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} else {
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count &= 0xffffff;
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res = calc_linear_pos(viadev, idx, count);
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}
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} else {
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res = viadev->hwptr_done;
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if (!viadev->in_interrupt) {
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if (status & VIA_REG_STAT_EOL) {
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res = 0;
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} else
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if (status & VIA_REG_STAT_FLAG) {
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res += viadev->fragsize;
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}
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}
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}
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unlock:
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viadev->lastpos = res;
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spin_unlock(&chip->reg_lock);
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return bytes_to_frames(substream->runtime, res);
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@ -1241,9 +1329,10 @@ static snd_pcm_ops_t snd_via8233_capture_ops = {
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};
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static void init_viadev(via82xx_t *chip, int idx, unsigned int reg_offset, int direction)
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static void init_viadev(via82xx_t *chip, int idx, unsigned int reg_offset, int shadow_pos, int direction)
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{
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chip->devs[idx].reg_offset = reg_offset;
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chip->devs[idx].shadow_shift = shadow_pos * 4;
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chip->devs[idx].direction = direction;
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chip->devs[idx].port = chip->port + reg_offset;
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}
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@ -1273,9 +1362,9 @@ static int __devinit snd_via8233_pcm_new(via82xx_t *chip)
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chip->pcms[0] = pcm;
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/* set up playbacks */
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for (i = 0; i < 4; i++)
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init_viadev(chip, i, 0x10 * i, 0);
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init_viadev(chip, i, 0x10 * i, i, 0);
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/* capture */
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init_viadev(chip, chip->capture_devno, VIA_REG_CAPTURE_8233_STATUS, 1);
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init_viadev(chip, chip->capture_devno, VIA_REG_CAPTURE_8233_STATUS, 6, 1);
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if ((err = snd_pcm_lib_preallocate_pages_for_all(pcm, SNDRV_DMA_TYPE_DEV_SG,
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snd_dma_pci_data(chip->pci), 64*1024, 128*1024)) < 0)
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@ -1291,9 +1380,9 @@ static int __devinit snd_via8233_pcm_new(via82xx_t *chip)
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strcpy(pcm->name, chip->card->shortname);
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chip->pcms[1] = pcm;
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/* set up playback */
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init_viadev(chip, chip->multi_devno, VIA_REG_MULTPLAY_STATUS, 0);
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init_viadev(chip, chip->multi_devno, VIA_REG_MULTPLAY_STATUS, 4, 0);
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/* set up capture */
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init_viadev(chip, chip->capture_devno + 1, VIA_REG_CAPTURE_8233_STATUS + 0x10, 1);
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init_viadev(chip, chip->capture_devno + 1, VIA_REG_CAPTURE_8233_STATUS + 0x10, 7, 1);
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if ((err = snd_pcm_lib_preallocate_pages_for_all(pcm, SNDRV_DMA_TYPE_DEV_SG,
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snd_dma_pci_data(chip->pci), 64*1024, 128*1024)) < 0)
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@ -1326,9 +1415,9 @@ static int __devinit snd_via8233a_pcm_new(via82xx_t *chip)
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strcpy(pcm->name, chip->card->shortname);
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chip->pcms[0] = pcm;
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/* set up playback */
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init_viadev(chip, chip->multi_devno, VIA_REG_MULTPLAY_STATUS, 0);
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init_viadev(chip, chip->multi_devno, VIA_REG_MULTPLAY_STATUS, 4, 0);
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/* capture */
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init_viadev(chip, chip->capture_devno, VIA_REG_CAPTURE_8233_STATUS, 1);
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init_viadev(chip, chip->capture_devno, VIA_REG_CAPTURE_8233_STATUS, 6, 1);
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if ((err = snd_pcm_lib_preallocate_pages_for_all(pcm, SNDRV_DMA_TYPE_DEV_SG,
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snd_dma_pci_data(chip->pci), 64*1024, 128*1024)) < 0)
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@ -1347,7 +1436,7 @@ static int __devinit snd_via8233a_pcm_new(via82xx_t *chip)
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strcpy(pcm->name, chip->card->shortname);
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chip->pcms[1] = pcm;
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/* set up playback */
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init_viadev(chip, chip->playback_devno, 0x30, 0);
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init_viadev(chip, chip->playback_devno, 0x30, 3, 0);
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if ((err = snd_pcm_lib_preallocate_pages_for_all(pcm, SNDRV_DMA_TYPE_DEV_SG,
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snd_dma_pci_data(chip->pci), 64*1024, 128*1024)) < 0)
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@ -1377,8 +1466,8 @@ static int __devinit snd_via686_pcm_new(via82xx_t *chip)
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pcm->private_data = chip;
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strcpy(pcm->name, chip->card->shortname);
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chip->pcms[0] = pcm;
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init_viadev(chip, 0, VIA_REG_PLAYBACK_STATUS, 0);
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init_viadev(chip, 1, VIA_REG_CAPTURE_STATUS, 1);
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init_viadev(chip, 0, VIA_REG_PLAYBACK_STATUS, 0, 0);
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init_viadev(chip, 1, VIA_REG_CAPTURE_STATUS, 0, 1);
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if ((err = snd_pcm_lib_preallocate_pages_for_all(pcm, SNDRV_DMA_TYPE_DEV_SG,
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snd_dma_pci_data(chip->pci), 64*1024, 128*1024)) < 0)
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@ -2134,7 +2223,10 @@ static int __devinit snd_via82xx_create(snd_card_t * card,
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return err;
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}
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chip->port = pci_resource_start(pci, 0);
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if (request_irq(pci->irq, snd_via82xx_interrupt, SA_INTERRUPT|SA_SHIRQ,
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if (request_irq(pci->irq,
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chip_type == TYPE_VIA8233 ?
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snd_via8233_interrupt : snd_via686_interrupt,
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SA_INTERRUPT|SA_SHIRQ,
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card->driver, (void *)chip)) {
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snd_printk("unable to grab IRQ %d\n", pci->irq);
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snd_via82xx_free(chip);
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