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![Thomas Gleixner](/assets/img/avatar_default.png)
The hrtimer callback pcsp_do_timer() prepares rearming of the timer with hrtimer_forward(). hrtimer_forward() is intended to provide a mechanism to forward the expiry time of the hrtimer by a multiple of the period argument so that the expiry time greater than the time provided in the 'now' argument. pcsp_do_timer() invokes hrtimer_forward() with the current timer expiry time as 'now' argument. That's providing a periodic timer expiry, but is not really robust when the timer callback is delayed so that the resulting new expiry time is already in the past which causes the callback to be invoked immediately again. If the timer is delayed then the back to back invocation is not really making it better than skipping the missed periods. Sound is distorted in any case. Use hrtimer_forward_now() which ensures that the next expiry is in the future. This prevents hogging the CPU in the timer expiry code and allows later on to remove hrtimer_forward() from the public interfaces. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Cc: alsa-devel@alsa-project.org Cc: Takashi Iwai <tiwai@suse.com> Cc: Jaroslav Kysela <perex@perex.cz> Link: https://lore.kernel.org/r/20210923153339.623208460@linutronix.de Signed-off-by: Takashi Iwai <tiwai@suse.de>
352 lines
8.8 KiB
C
352 lines
8.8 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/*
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* PC-Speaker driver for Linux
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*
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* Copyright (C) 1993-1997 Michael Beck
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* Copyright (C) 1997-2001 David Woodhouse
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* Copyright (C) 2001-2008 Stas Sergeev
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*/
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#include <linux/module.h>
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#include <linux/gfp.h>
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#include <linux/moduleparam.h>
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#include <linux/interrupt.h>
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#include <linux/io.h>
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#include <sound/pcm.h>
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#include "pcsp.h"
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static bool nforce_wa;
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module_param(nforce_wa, bool, 0444);
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MODULE_PARM_DESC(nforce_wa, "Apply NForce chipset workaround "
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"(expect bad sound)");
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#define DMIX_WANTS_S16 1
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/*
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* Call snd_pcm_period_elapsed in a work
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* This avoids spinlock messes and long-running irq contexts
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*/
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static void pcsp_call_pcm_elapsed(struct work_struct *work)
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{
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if (atomic_read(&pcsp_chip.timer_active)) {
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struct snd_pcm_substream *substream;
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substream = pcsp_chip.playback_substream;
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if (substream)
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snd_pcm_period_elapsed(substream);
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}
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}
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static DECLARE_WORK(pcsp_pcm_work, pcsp_call_pcm_elapsed);
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/* write the port and returns the next expire time in ns;
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* called at the trigger-start and in hrtimer callback
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*/
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static u64 pcsp_timer_update(struct snd_pcsp *chip)
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{
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unsigned char timer_cnt, val;
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u64 ns;
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struct snd_pcm_substream *substream;
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struct snd_pcm_runtime *runtime;
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unsigned long flags;
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if (chip->thalf) {
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outb(chip->val61, 0x61);
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chip->thalf = 0;
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return chip->ns_rem;
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}
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substream = chip->playback_substream;
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if (!substream)
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return 0;
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runtime = substream->runtime;
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/* assume it is mono! */
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val = runtime->dma_area[chip->playback_ptr + chip->fmt_size - 1];
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if (chip->is_signed)
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val ^= 0x80;
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timer_cnt = val * CUR_DIV() / 256;
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if (timer_cnt && chip->enable) {
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raw_spin_lock_irqsave(&i8253_lock, flags);
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if (!nforce_wa) {
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outb_p(chip->val61, 0x61);
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outb_p(timer_cnt, 0x42);
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outb(chip->val61 ^ 1, 0x61);
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} else {
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outb(chip->val61 ^ 2, 0x61);
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chip->thalf = 1;
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}
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raw_spin_unlock_irqrestore(&i8253_lock, flags);
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}
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chip->ns_rem = PCSP_PERIOD_NS();
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ns = (chip->thalf ? PCSP_CALC_NS(timer_cnt) : chip->ns_rem);
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chip->ns_rem -= ns;
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return ns;
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}
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static void pcsp_pointer_update(struct snd_pcsp *chip)
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{
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struct snd_pcm_substream *substream;
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size_t period_bytes, buffer_bytes;
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int periods_elapsed;
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unsigned long flags;
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/* update the playback position */
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substream = chip->playback_substream;
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if (!substream)
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return;
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period_bytes = snd_pcm_lib_period_bytes(substream);
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buffer_bytes = snd_pcm_lib_buffer_bytes(substream);
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spin_lock_irqsave(&chip->substream_lock, flags);
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chip->playback_ptr += PCSP_INDEX_INC() * chip->fmt_size;
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periods_elapsed = chip->playback_ptr - chip->period_ptr;
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if (periods_elapsed < 0) {
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#if PCSP_DEBUG
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printk(KERN_INFO "PCSP: buffer_bytes mod period_bytes != 0 ? "
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"(%zi %zi %zi)\n",
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chip->playback_ptr, period_bytes, buffer_bytes);
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#endif
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periods_elapsed += buffer_bytes;
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}
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periods_elapsed /= period_bytes;
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/* wrap the pointer _before_ calling snd_pcm_period_elapsed(),
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* or ALSA will BUG on us. */
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chip->playback_ptr %= buffer_bytes;
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if (periods_elapsed) {
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chip->period_ptr += periods_elapsed * period_bytes;
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chip->period_ptr %= buffer_bytes;
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queue_work(system_highpri_wq, &pcsp_pcm_work);
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}
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spin_unlock_irqrestore(&chip->substream_lock, flags);
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}
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enum hrtimer_restart pcsp_do_timer(struct hrtimer *handle)
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{
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struct snd_pcsp *chip = container_of(handle, struct snd_pcsp, timer);
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int pointer_update;
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u64 ns;
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if (!atomic_read(&chip->timer_active) || !chip->playback_substream)
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return HRTIMER_NORESTART;
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pointer_update = !chip->thalf;
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ns = pcsp_timer_update(chip);
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if (!ns) {
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printk(KERN_WARNING "PCSP: unexpected stop\n");
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return HRTIMER_NORESTART;
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}
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if (pointer_update)
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pcsp_pointer_update(chip);
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hrtimer_forward_now(handle, ns_to_ktime(ns));
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return HRTIMER_RESTART;
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}
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static int pcsp_start_playing(struct snd_pcsp *chip)
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{
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#if PCSP_DEBUG
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printk(KERN_INFO "PCSP: start_playing called\n");
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#endif
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if (atomic_read(&chip->timer_active)) {
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printk(KERN_ERR "PCSP: Timer already active\n");
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return -EIO;
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}
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raw_spin_lock(&i8253_lock);
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chip->val61 = inb(0x61) | 0x03;
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outb_p(0x92, 0x43); /* binary, mode 1, LSB only, ch 2 */
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raw_spin_unlock(&i8253_lock);
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atomic_set(&chip->timer_active, 1);
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chip->thalf = 0;
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hrtimer_start(&pcsp_chip.timer, 0, HRTIMER_MODE_REL);
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return 0;
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}
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static void pcsp_stop_playing(struct snd_pcsp *chip)
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{
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#if PCSP_DEBUG
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printk(KERN_INFO "PCSP: stop_playing called\n");
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#endif
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if (!atomic_read(&chip->timer_active))
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return;
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atomic_set(&chip->timer_active, 0);
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raw_spin_lock(&i8253_lock);
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/* restore the timer */
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outb_p(0xb6, 0x43); /* binary, mode 3, LSB/MSB, ch 2 */
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outb(chip->val61 & 0xFC, 0x61);
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raw_spin_unlock(&i8253_lock);
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}
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/*
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* Force to stop and sync the stream
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*/
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void pcsp_sync_stop(struct snd_pcsp *chip)
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{
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local_irq_disable();
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pcsp_stop_playing(chip);
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local_irq_enable();
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hrtimer_cancel(&chip->timer);
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cancel_work_sync(&pcsp_pcm_work);
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}
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static int snd_pcsp_playback_close(struct snd_pcm_substream *substream)
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{
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struct snd_pcsp *chip = snd_pcm_substream_chip(substream);
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#if PCSP_DEBUG
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printk(KERN_INFO "PCSP: close called\n");
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#endif
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pcsp_sync_stop(chip);
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chip->playback_substream = NULL;
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return 0;
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}
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static int snd_pcsp_playback_hw_params(struct snd_pcm_substream *substream,
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struct snd_pcm_hw_params *hw_params)
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{
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struct snd_pcsp *chip = snd_pcm_substream_chip(substream);
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pcsp_sync_stop(chip);
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return 0;
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}
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static int snd_pcsp_playback_hw_free(struct snd_pcm_substream *substream)
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{
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struct snd_pcsp *chip = snd_pcm_substream_chip(substream);
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#if PCSP_DEBUG
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printk(KERN_INFO "PCSP: hw_free called\n");
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#endif
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pcsp_sync_stop(chip);
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return 0;
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}
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static int snd_pcsp_playback_prepare(struct snd_pcm_substream *substream)
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{
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struct snd_pcsp *chip = snd_pcm_substream_chip(substream);
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pcsp_sync_stop(chip);
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chip->playback_ptr = 0;
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chip->period_ptr = 0;
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chip->fmt_size =
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snd_pcm_format_physical_width(substream->runtime->format) >> 3;
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chip->is_signed = snd_pcm_format_signed(substream->runtime->format);
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#if PCSP_DEBUG
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printk(KERN_INFO "PCSP: prepare called, "
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"size=%zi psize=%zi f=%zi f1=%i fsize=%i\n",
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snd_pcm_lib_buffer_bytes(substream),
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snd_pcm_lib_period_bytes(substream),
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snd_pcm_lib_buffer_bytes(substream) /
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snd_pcm_lib_period_bytes(substream),
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substream->runtime->periods,
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chip->fmt_size);
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#endif
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return 0;
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}
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static int snd_pcsp_trigger(struct snd_pcm_substream *substream, int cmd)
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{
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struct snd_pcsp *chip = snd_pcm_substream_chip(substream);
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#if PCSP_DEBUG
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printk(KERN_INFO "PCSP: trigger called\n");
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#endif
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switch (cmd) {
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case SNDRV_PCM_TRIGGER_START:
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case SNDRV_PCM_TRIGGER_RESUME:
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return pcsp_start_playing(chip);
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case SNDRV_PCM_TRIGGER_STOP:
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case SNDRV_PCM_TRIGGER_SUSPEND:
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pcsp_stop_playing(chip);
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break;
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default:
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return -EINVAL;
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}
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return 0;
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}
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static snd_pcm_uframes_t snd_pcsp_playback_pointer(struct snd_pcm_substream
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*substream)
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{
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struct snd_pcsp *chip = snd_pcm_substream_chip(substream);
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unsigned int pos;
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spin_lock(&chip->substream_lock);
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pos = chip->playback_ptr;
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spin_unlock(&chip->substream_lock);
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return bytes_to_frames(substream->runtime, pos);
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}
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static const struct snd_pcm_hardware snd_pcsp_playback = {
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.info = (SNDRV_PCM_INFO_INTERLEAVED |
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SNDRV_PCM_INFO_HALF_DUPLEX |
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SNDRV_PCM_INFO_MMAP | SNDRV_PCM_INFO_MMAP_VALID),
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.formats = (SNDRV_PCM_FMTBIT_U8
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#if DMIX_WANTS_S16
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| SNDRV_PCM_FMTBIT_S16_LE
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#endif
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),
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.rates = SNDRV_PCM_RATE_KNOT,
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.rate_min = PCSP_DEFAULT_SRATE,
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.rate_max = PCSP_DEFAULT_SRATE,
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.channels_min = 1,
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.channels_max = 1,
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.buffer_bytes_max = PCSP_BUFFER_SIZE,
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.period_bytes_min = 64,
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.period_bytes_max = PCSP_MAX_PERIOD_SIZE,
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.periods_min = 2,
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.periods_max = PCSP_MAX_PERIODS,
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.fifo_size = 0,
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};
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static int snd_pcsp_playback_open(struct snd_pcm_substream *substream)
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{
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struct snd_pcsp *chip = snd_pcm_substream_chip(substream);
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struct snd_pcm_runtime *runtime = substream->runtime;
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#if PCSP_DEBUG
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printk(KERN_INFO "PCSP: open called\n");
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#endif
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if (atomic_read(&chip->timer_active)) {
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printk(KERN_ERR "PCSP: still active!!\n");
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return -EBUSY;
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}
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runtime->hw = snd_pcsp_playback;
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chip->playback_substream = substream;
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return 0;
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}
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static const struct snd_pcm_ops snd_pcsp_playback_ops = {
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.open = snd_pcsp_playback_open,
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.close = snd_pcsp_playback_close,
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.hw_params = snd_pcsp_playback_hw_params,
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.hw_free = snd_pcsp_playback_hw_free,
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.prepare = snd_pcsp_playback_prepare,
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.trigger = snd_pcsp_trigger,
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.pointer = snd_pcsp_playback_pointer,
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};
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int snd_pcsp_new_pcm(struct snd_pcsp *chip)
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{
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int err;
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err = snd_pcm_new(chip->card, "pcspeaker", 0, 1, 0, &chip->pcm);
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if (err < 0)
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return err;
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snd_pcm_set_ops(chip->pcm, SNDRV_PCM_STREAM_PLAYBACK,
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&snd_pcsp_playback_ops);
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chip->pcm->private_data = chip;
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chip->pcm->info_flags = SNDRV_PCM_INFO_HALF_DUPLEX;
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strcpy(chip->pcm->name, "pcsp");
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snd_pcm_set_managed_buffer_all(chip->pcm,
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SNDRV_DMA_TYPE_CONTINUOUS,
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NULL,
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PCSP_BUFFER_SIZE,
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PCSP_BUFFER_SIZE);
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return 0;
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}
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