内核的文件参考下：s3c24xx-i2s.c ，来自2.6.29

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本文介绍了一种用于 S3C24xx 系列微处理器的 I2S (Inter-IC Sound) 音频接口驱动实现。该驱动支持 ALSA (Advanced Linux Sound Architecture) 层，能够实现立体声音频数据的 DMA 传输。文中详细描述了 I2S 控制寄存器的配置方法，包括时钟源设置、采样率配置及数据格式等。

/* * s3c24xx-i2s.c -- ALSA Soc Audio Layer * * (c) 2006 Wolfson Microelectronics PLC. * Graeme Gregory graeme.gregory@wolfsonmicro.com or linux@wolfsonmicro.com * * (c) 2004-2005 Simtec Electronics * http://armlinux.simtec.co.uk/ * Ben Dooks <ben@simtec.co.uk> * * This program is free software; you can redistribute it and/or modify it * under the terms of the GNU General Public License as published by the * Free Software Foundation; either version 2 of the License, or (at your * option) any later version. */ #include <linux/init.h> #include <linux/module.h> #include <linux/device.h> #include <linux/delay.h> #include <linux/clk.h> #include <linux/jiffies.h> #include <linux/io.h> #include <sound/core.h> #include <sound/pcm.h> #include <sound/pcm_params.h> #include <sound/initval.h> #include <sound/soc.h> #include <mach/hardware.h> #include <mach/regs-gpio.h> #include <mach/regs-clock.h> #include <mach/audio.h> #include <asm/dma.h> #include <mach/dma.h> #include <asm/plat-s3c24xx/regs-iis.h> #include "s3c24xx-pcm.h" #include "s3c24xx-i2s.h" #define S3C24XX_I2S_DEBUG 0 #if S3C24XX_I2S_DEBUG #define DBG(x...) printk(KERN_DEBUG "s3c24xx-i2s: " x) #else #define DBG(x...) #endif static struct s3c2410_dma_client s3c24xx_dma_client_out = { .name = "I2S PCM Stereo out" }; static struct s3c2410_dma_client s3c24xx_dma_client_in = { .name = "I2S PCM Stereo in" }; static struct s3c24xx_pcm_dma_params s3c24xx_i2s_pcm_stereo_out = { .client = &s3c24xx_dma_client_out, .channel = DMACH_I2S_OUT, .dma_addr = S3C2410_PA_IIS + S3C2410_IISFIFO, .dma_size = 2, }; static struct s3c24xx_pcm_dma_params s3c24xx_i2s_pcm_stereo_in = { .client = &s3c24xx_dma_client_in, .channel = DMACH_I2S_IN, .dma_addr = S3C2410_PA_IIS + S3C2410_IISFIFO, .dma_size = 2, }; struct s3c24xx_i2s_info { void __iomem *regs; struct clk *iis_clk; u32 iiscon; u32 iismod; u32 iisfcon; u32 iispsr; }; static struct s3c24xx_i2s_info s3c24xx_i2s; static void s3c24xx_snd_txctrl(int on) { u32 iisfcon; u32 iiscon; u32 iismod; DBG("Entered %s/n", __func__); iisfcon = readl(s3c24xx_i2s.regs + S3C2410_IISFCON); iiscon = readl(s3c24xx_i2s.regs + S3C2410_IISCON); iismod = readl(s3c24xx_i2s.regs + S3C2410_IISMOD); DBG("r: IISCON: %lx IISMOD: %lx IISFCON: %lx/n", iiscon, iismod, iisfcon); if (on) { iisfcon |= S3C2410_IISFCON_TXDMA | S3C2410_IISFCON_TXENABLE; iiscon |= S3C2410_IISCON_TXDMAEN | S3C2410_IISCON_IISEN; iiscon &= ~S3C2410_IISCON_TXIDLE; iismod |= S3C2410_IISMOD_TXMODE; writel(iismod, s3c24xx_i2s.regs + S3C2410_IISMOD); writel(iisfcon, s3c24xx_i2s.regs + S3C2410_IISFCON); writel(iiscon, s3c24xx_i2s.regs + S3C2410_IISCON); } else { /* note, we have to disable the FIFOs otherwise bad things * seem to happen when the DMA stops. According to the * Samsung supplied kernel, this should allow the DMA * engine and FIFOs to reset. If this isn't allowed, the * DMA engine will simply freeze randomly. */ iisfcon &= ~S3C2410_IISFCON_TXENABLE; iisfcon &= ~S3C2410_IISFCON_TXDMA; iiscon |= S3C2410_IISCON_TXIDLE; iiscon &= ~S3C2410_IISCON_TXDMAEN; iismod &= ~S3C2410_IISMOD_TXMODE; writel(iiscon, s3c24xx_i2s.regs + S3C2410_IISCON); writel(iisfcon, s3c24xx_i2s.regs + S3C2410_IISFCON); writel(iismod, s3c24xx_i2s.regs + S3C2410_IISMOD); } DBG("w: IISCON: %lx IISMOD: %lx IISFCON: %lx/n", iiscon, iismod, iisfcon); } static void s3c24xx_snd_rxctrl(int on) { u32 iisfcon; u32 iiscon; u32 iismod; DBG("Entered %s/n", __func__); iisfcon = readl(s3c24xx_i2s.regs + S3C2410_IISFCON); iiscon = readl(s3c24xx_i2s.regs + S3C2410_IISCON); iismod = readl(s3c24xx_i2s.regs + S3C2410_IISMOD); DBG("r: IISCON: %lx IISMOD: %lx IISFCON: %lx/n", iiscon, iismod, iisfcon); if (on) { iisfcon |= S3C2410_IISFCON_RXDMA | S3C2410_IISFCON_RXENABLE; iiscon |= S3C2410_IISCON_RXDMAEN | S3C2410_IISCON_IISEN; iiscon &= ~S3C2410_IISCON_RXIDLE; iismod |= S3C2410_IISMOD_RXMODE; writel(iismod, s3c24xx_i2s.regs + S3C2410_IISMOD); writel(iisfcon, s3c24xx_i2s.regs + S3C2410_IISFCON); writel(iiscon, s3c24xx_i2s.regs + S3C2410_IISCON); } else { /* note, we have to disable the FIFOs otherwise bad things * seem to happen when the DMA stops. According to the * Samsung supplied kernel, this should allow the DMA * engine and FIFOs to reset. If this isn't allowed, the * DMA engine will simply freeze randomly. */ iisfcon &= ~S3C2410_IISFCON_RXENABLE; iisfcon &= ~S3C2410_IISFCON_RXDMA; iiscon |= S3C2410_IISCON_RXIDLE; iiscon &= ~S3C2410_IISCON_RXDMAEN; iismod &= ~S3C2410_IISMOD_RXMODE; writel(iisfcon, s3c24xx_i2s.regs + S3C2410_IISFCON); writel(iiscon, s3c24xx_i2s.regs + S3C2410_IISCON); writel(iismod, s3c24xx_i2s.regs + S3C2410_IISMOD); } DBG("w: IISCON: %lx IISMOD: %lx IISFCON: %lx/n", iiscon, iismod, iisfcon); } /* * Wait for the LR signal to allow synchronisation to the L/R clock * from the codec. May only be needed for slave mode. */ static int s3c24xx_snd_lrsync(void) { u32 iiscon; int timeout = 50; /* 5ms */ DBG("Entered %s/n", __func__); while (1) { iiscon = readl(s3c24xx_i2s.regs + S3C2410_IISCON); if (iiscon & S3C2410_IISCON_LRINDEX) break; if (!timeout--) return -ETIMEDOUT; udelay(100); } return 0; } /* * Check whether CPU is the master or slave */ static inline int s3c24xx_snd_is_clkmaster(void) { DBG("Entered %s/n", __func__); return (readl(s3c24xx_i2s.regs + S3C2410_IISMOD) & S3C2410_IISMOD_SLAVE) ? 0:1; } /* * Set S3C24xx I2S DAI format */ static int s3c24xx_i2s_set_fmt(struct snd_soc_dai *cpu_dai, unsigned int fmt) { u32 iismod; DBG("Entered %s/n", __func__); iismod = readl(s3c24xx_i2s.regs + S3C2410_IISMOD); DBG("hw_params r: IISMOD: %lx /n", iismod); switch (fmt & SND_SOC_DAIFMT_MASTER_MASK) { case SND_SOC_DAIFMT_CBM_CFM: iismod |= S3C2410_IISMOD_SLAVE; break; case SND_SOC_DAIFMT_CBS_CFS: iismod &= ~S3C2410_IISMOD_SLAVE; break; default: return -EINVAL; } switch (fmt & SND_SOC_DAIFMT_FORMAT_MASK) { case SND_SOC_DAIFMT_LEFT_J: iismod |= S3C2410_IISMOD_MSB; break; case SND_SOC_DAIFMT_I2S: iismod &= ~S3C2410_IISMOD_MSB; break; default: return -EINVAL; } writel(iismod, s3c24xx_i2s.regs + S3C2410_IISMOD); DBG("hw_params w: IISMOD: %lx /n", iismod); return 0; } static int s3c24xx_i2s_hw_params(struct snd_pcm_substream *substream, struct snd_pcm_hw_params *params, struct snd_soc_dai *dai) { struct snd_soc_pcm_runtime *rtd = substream->private_data; u32 iismod; DBG("Entered %s/n", __func__); if (substream->stream == SNDRV_PCM_STREAM_PLAYBACK) rtd->dai->cpu_dai->dma_data = &s3c24xx_i2s_pcm_stereo_out; else rtd->dai->cpu_dai->dma_data = &s3c24xx_i2s_pcm_stereo_in; /* Working copies of register */ iismod = readl(s3c24xx_i2s.regs + S3C2410_IISMOD); DBG("hw_params r: IISMOD: %lx/n", iismod); switch (params_format(params)) { case SNDRV_PCM_FORMAT_S8: iismod &= ~S3C2410_IISMOD_16BIT; ((struct s3c24xx_pcm_dma_params *) rtd->dai->cpu_dai->dma_data)->dma_size = 1; break; case SNDRV_PCM_FORMAT_S16_LE: iismod |= S3C2410_IISMOD_16BIT; ((struct s3c24xx_pcm_dma_params *) rtd->dai->cpu_dai->dma_data)->dma_size = 2; break; default: return -EINVAL; } writel(iismod, s3c24xx_i2s.regs + S3C2410_IISMOD); DBG("hw_params w: IISMOD: %lx/n", iismod); return 0; } static int s3c24xx_i2s_trigger(struct snd_pcm_substream *substream, int cmd, struct snd_soc_dai *dai) { int ret = 0; DBG("Entered %s/n", __func__); switch (cmd) { case SNDRV_PCM_TRIGGER_START: case SNDRV_PCM_TRIGGER_RESUME: case SNDRV_PCM_TRIGGER_PAUSE_RELEASE: if (!s3c24xx_snd_is_clkmaster()) { ret = s3c24xx_snd_lrsync(); if (ret) goto exit_err; } if (substream->stream == SNDRV_PCM_STREAM_CAPTURE) s3c24xx_snd_rxctrl(1); else s3c24xx_snd_txctrl(1); break; case SNDRV_PCM_TRIGGER_STOP: case SNDRV_PCM_TRIGGER_SUSPEND: case SNDRV_PCM_TRIGGER_PAUSE_PUSH: if (substream->stream == SNDRV_PCM_STREAM_CAPTURE) s3c24xx_snd_rxctrl(0); else s3c24xx_snd_txctrl(0); break; default: ret = -EINVAL; break; } exit_err: return ret; } /* * Set S3C24xx Clock source */ static int s3c24xx_i2s_set_sysclk(struct snd_soc_dai *cpu_dai, int clk_id, unsigned int freq, int dir) { u32 iismod = readl(s3c24xx_i2s.regs + S3C2410_IISMOD); DBG("Entered %s/n", __func__); iismod &= ~S3C2440_IISMOD_MPLL; switch (clk_id) { case S3C24XX_CLKSRC_PCLK: break; case S3C24XX_CLKSRC_MPLL: iismod |= S3C2440_IISMOD_MPLL; break; default: return -EINVAL; } writel(iismod, s3c24xx_i2s.regs + S3C2410_IISMOD); return 0; } /* * Set S3C24xx Clock dividers */ static int s3c24xx_i2s_set_clkdiv(struct snd_soc_dai *cpu_dai, int div_id, int div) { u32 reg; DBG("Entered %s/n", __func__); switch (div_id) { case S3C24XX_DIV_BCLK: reg = readl(s3c24xx_i2s.regs + S3C2410_IISMOD) & ~S3C2410_IISMOD_FS_MASK; writel(reg | div, s3c24xx_i2s.regs + S3C2410_IISMOD); break; case S3C24XX_DIV_MCLK: reg = readl(s3c24xx_i2s.regs + S3C2410_IISMOD) & ~(S3C2410_IISMOD_384FS); writel(reg | div, s3c24xx_i2s.regs + S3C2410_IISMOD); break; case S3C24XX_DIV_PRESCALER: writel(div, s3c24xx_i2s.regs + S3C2410_IISPSR); reg = readl(s3c24xx_i2s.regs + S3C2410_IISCON); writel(reg | S3C2410_IISCON_PSCEN, s3c24xx_i2s.regs + S3C2410_IISCON); break; default: return -EINVAL; } return 0; } /* * To avoid duplicating clock code, allow machine driver to * get the clockrate from here. */ u32 s3c24xx_i2s_get_clockrate(void) { return clk_get_rate(s3c24xx_i2s.iis_clk); } EXPORT_SYMBOL_GPL(s3c24xx_i2s_get_clockrate); static int s3c24xx_i2s_probe(struct platform_device *pdev, struct snd_soc_dai *dai) { DBG("Entered %s/n", __func__); s3c24xx_i2s.regs = ioremap(S3C2410_PA_IIS, 0x100); if (s3c24xx_i2s.regs == NULL) return -ENXIO; s3c24xx_i2s.iis_clk = clk_get(&pdev->dev, "iis"); if (s3c24xx_i2s.iis_clk == NULL) { DBG("failed to get iis_clock/n"); iounmap(s3c24xx_i2s.regs); return -ENODEV; } clk_enable(s3c24xx_i2s.iis_clk); /* Configure the I2S pins in correct mode */ s3c2410_gpio_cfgpin(S3C2410_GPE0, S3C2410_GPE0_I2SLRCK); s3c2410_gpio_cfgpin(S3C2410_GPE1, S3C2410_GPE1_I2SSCLK); s3c2410_gpio_cfgpin(S3C2410_GPE2, S3C2410_GPE2_CDCLK); s3c2410_gpio_cfgpin(S3C2410_GPE3, S3C2410_GPE3_I2SSDI); s3c2410_gpio_cfgpin(S3C2410_GPE4, S3C2410_GPE4_I2SSDO); writel(S3C2410_IISCON_IISEN, s3c24xx_i2s.regs + S3C2410_IISCON); s3c24xx_snd_txctrl(0); s3c24xx_snd_rxctrl(0); return 0; } #ifdef CONFIG_PM static int s3c24xx_i2s_suspend(struct snd_soc_dai *cpu_dai) { DBG("Entered %s/n", __func__); s3c24xx_i2s.iiscon = readl(s3c24xx_i2s.regs + S3C2410_IISCON); s3c24xx_i2s.iismod = readl(s3c24xx_i2s.regs + S3C2410_IISMOD); s3c24xx_i2s.iisfcon = readl(s3c24xx_i2s.regs + S3C2410_IISFCON); s3c24xx_i2s.iispsr = readl(s3c24xx_i2s.regs + S3C2410_IISPSR); clk_disable(s3c24xx_i2s.iis_clk); return 0; } static int s3c24xx_i2s_resume(struct snd_soc_dai *cpu_dai) { DBG("Entered %s/n", __func__); clk_enable(s3c24xx_i2s.iis_clk); writel(s3c24xx_i2s.iiscon, s3c24xx_i2s.regs + S3C2410_IISCON); writel(s3c24xx_i2s.iismod, s3c24xx_i2s.regs + S3C2410_IISMOD); writel(s3c24xx_i2s.iisfcon, s3c24xx_i2s.regs + S3C2410_IISFCON); writel(s3c24xx_i2s.iispsr, s3c24xx_i2s.regs + S3C2410_IISPSR); return 0; } #else #define s3c24xx_i2s_suspend NULL #define s3c24xx_i2s_resume NULL #endif #define S3C24XX_I2S_RATES / (SNDRV_PCM_RATE_8000 | SNDRV_PCM_RATE_11025 | SNDRV_PCM_RATE_16000 | / SNDRV_PCM_RATE_22050 | SNDRV_PCM_RATE_32000 | SNDRV_PCM_RATE_44100 | / SNDRV_PCM_RATE_48000 | SNDRV_PCM_RATE_88200 | SNDRV_PCM_RATE_96000) struct snd_soc_dai s3c24xx_i2s_dai = { .name = "s3c24xx-i2s", .id = 0, .probe = s3c24xx_i2s_probe, .suspend = s3c24xx_i2s_suspend, .resume = s3c24xx_i2s_resume, .playback = { .channels_min = 2, .channels_max = 2, .rates = S3C24XX_I2S_RATES, .formats = SNDRV_PCM_FMTBIT_S8 | SNDRV_PCM_FMTBIT_S16_LE,}, .capture = { .channels_min = 2, .channels_max = 2, .rates = S3C24XX_I2S_RATES, .formats = SNDRV_PCM_FMTBIT_S8 | SNDRV_PCM_FMTBIT_S16_LE,}, .ops = { .trigger = s3c24xx_i2s_trigger, .hw_params = s3c24xx_i2s_hw_params, .set_fmt = s3c24xx_i2s_set_fmt, .set_clkdiv = s3c24xx_i2s_set_clkdiv, .set_sysclk = s3c24xx_i2s_set_sysclk, }, }; EXPORT_SYMBOL_GPL(s3c24xx_i2s_dai); static int __init s3c24xx_i2s_init(void) { return snd_soc_register_dai(&s3c24xx_i2s_dai); } module_init(s3c24xx_i2s_init); static void __exit s3c24xx_i2s_exit(void) { snd_soc_unregister_dai(&s3c24xx_i2s_dai); } module_exit(s3c24xx_i2s_exit); /* Module information */ MODULE_AUTHOR("Ben Dooks, <ben@simtec.co.uk>"); MODULE_DESCRIPTION("s3c24xx I2S SoC Interface"); MODULE_LICENSE("GPL");