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Message-ID: <1384776479.14845.208.camel@smile>
Date: Mon, 18 Nov 2013 12:08:22 +0000
From: "Shevchenko, Andriy" <andriy.shevchenko@...el.com>
To: Florian Meier <florian.meier@...lo.de>
CC: Liam Girdwood <lgirdwood@...il.com>,
Mark Brown <broonie@...nel.org>,
Stephen Warren <swarren@...dotorg.org>,
Lars-Peter Clausen <lars@...afoo.de>,
"alsa-devel@...a-project.org" <alsa-devel@...a-project.org>,
linux-rpi-kernel <linux-rpi-kernel@...ts.infradead.org>,
devicetree <devicetree@...r.kernel.org>,
dmaengine <dmaengine@...r.kernel.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"linux-arm-kernel@...ts.infradead.org"
<linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCHv3] ASoC: Add support for BCM2835
On Mon, 2013-11-18 at 12:28 +0100, Florian Meier wrote:
> This driver adds support for digital audio (I2S)
> for the BCM2835 SoC that is used by the
> Raspberry Pi. External audio codecs can be
> connected to the Raspberry Pi via P5 header.
>
> It relies on cyclic DMA engine support for BCM2835.
Few comments below.
[]
> +static void bcm2835_i2s_stop_clock(struct bcm2835_i2s_dev *dev)
> +{
> + uint32_t clkreg;
> + int timeout = 1000;
> +
> + /* Stop clock */
> + regmap_update_bits(dev->clk_regmap, BCM2835_CLK_PCMCTL_REG,
> + BCM2835_CLK_PASSWD_MASK | BCM2835_CLK_ENAB,
> + BCM2835_CLK_PASSWD);
> +
> + /* Wait for the BUSY flag going down */
> + while (timeout > 0) {
> + timeout--;
while (--timeout) {
> +
> + regmap_read(dev->clk_regmap, BCM2835_CLK_PCMCTL_REG, &clkreg);
> + if (!(clkreg & BCM2835_CLK_BUSY))
> + break;
> + }
> +
> + if (timeout <= 0) {
if (!timeout) {
[]
> +static void bcm2835_i2s_clear_fifos(struct bcm2835_i2s_dev *dev,
> + bool tx, bool rx)
> +{
[]
> + /* Wait for the SYNC flag changing it's state */
> + while (timeout > 0) {
> + timeout--;
while (--timeout) {
> + regmap_read(dev->i2s_regmap, BCM2835_I2S_CS_A_REG, &csreg);
> + if ((csreg & BCM2835_I2S_SYNC) != syncval)
> + break;
> + }
> +
> + if (timeout <= 0)
if (!timeout)
[]
> +static int bcm2835_i2s_hw_params(struct snd_pcm_substream *substream,
> + struct snd_pcm_hw_params *params,
> + struct snd_soc_dai *dai)
> +{
> + struct bcm2835_i2s_dev *dev = snd_soc_dai_get_drvdata(dai);
> +
> + unsigned int sampling_rate = params_rate(params);
> + unsigned int data_length, data_delay, bclk_ratio;
> + unsigned int ch1pos, ch2pos, mode, format;
> + unsigned int mash = BCM2835_CLK_MASH_1;
> + unsigned int divi, divf, target_frequency;
> + int clk_src = -1;
> + unsigned int master = dev->fmt & SND_SOC_DAIFMT_MASTER_MASK;
> + uint32_t bit_master = (master == SND_SOC_DAIFMT_CBS_CFS
> + || master == SND_SOC_DAIFMT_CBS_CFM);
bool ?
> +
> + uint32_t frame_master = (master == SND_SOC_DAIFMT_CBS_CFS
So, if master == SND_SOC_DAIFMT_CBS_CFS both bit_master and frame_master
will be true. Is it correct?
> + || master == SND_SOC_DAIFMT_CBM_CFS);
Ditto.
> + uint32_t csreg;
> +
> + /*
> + * If a stream is already enabled,
> + * the registers are already set properly.
> + */
> + regmap_read(dev->i2s_regmap, BCM2835_I2S_CS_A_REG, &csreg);
> +
> + if (csreg & (BCM2835_I2S_TXON | BCM2835_I2S_RXON))
> + return 0;
> +
> + if (bcm2835_clk_freq[clk_src] % target_frequency == 0
> + && bit_master && frame_master) {
> + divi = bcm2835_clk_freq[clk_src]/target_frequency;
> + divf = 0;
> + } else {
> + uint64_t dividend;
> +
> + if (!dev->bclk_ratio) {
> + /*
> + * Overwrite bclk_ratio, because the
> + * above trick is not needed or can
> + * not be used.
> + */
> + bclk_ratio = 2*data_length;
= 2 * data_length;
> + }
> +
> + target_frequency = sampling_rate*bclk_ratio;
> +
> + clk_src = BCM2835_CLK_SRC_PLLD;
> + mash = BCM2835_CLK_MASH_1;
> +
> + dividend = bcm2835_clk_freq[clk_src];
> + dividend *= 1024;
> + do_div(dividend, target_frequency);
> + divi = dividend / 1024;
> + divf = dividend % 1024;
1024 is a magic number?
Could you use shifts and bitwise ANDs here?
> + ch1pos = data_delay;
> + ch2pos = bclk_ratio/2+data_delay;
' / 2 + '
[]
> + mode |= BCM2835_I2S_FLEN(bclk_ratio-1);
> + mode |= BCM2835_I2S_FSLEN(bclk_ratio/2);
Ditto. Spaces are missed.
[]
> + case SND_SOC_DAIFMT_IB_IF:
> + /* Both - therefore, none for BCM*/
'M */'
> + break;
> + case SND_SOC_DAIFMT_NB_IF:
> + /*
> + * Invert only frame sync - therefore,
> + * Invert only bit clock for BCM
Something wrong with casing in the commentary.
> + */
> + mode |= BCM2835_I2S_CLKI;
> + break;
> + case SND_SOC_DAIFMT_IB_NF:
> + /*
> + * Invert only bit clock - therefore,
> + * Invert only frame sync for BCM
Ditto.
> + */
> + mode |= BCM2835_I2S_FSI;
> + break;
> + default:
> + return -EINVAL;
> + }
> +
> + regmap_write(dev->i2s_regmap, BCM2835_I2S_MODE_A_REG, mode);
> +
> +
Redundant empty line.
[]
> +
> + return 0;
> +}
> +
> +
Ditto.
[]
> +static int bcm2835_i2s_startup(struct snd_pcm_substream *substream,
> + struct snd_soc_dai *dai)
> +{
> + struct bcm2835_i2s_dev *dev = snd_soc_dai_get_drvdata(dai);
> +
> + if (!dai->active) {
> + /* Should this still be running stop it */
> + bcm2835_i2s_stop_clock(dev);
> +
> + /* Enable PCM block */
> + regmap_update_bits(dev->i2s_regmap, BCM2835_I2S_CS_A_REG,
> + BCM2835_I2S_EN, BCM2835_I2S_EN);
> +
> + /*
> + * Disable STBY
Dot is missing?
> + * Requires at least 4 PCM clock cycles to take effect
> + */
> + regmap_update_bits(dev->i2s_regmap, BCM2835_I2S_CS_A_REG,
> + BCM2835_I2S_STBY, BCM2835_I2S_STBY);
> + }
> +
> + return 0;
> +}
> +static void bcm2835_i2s_shutdown(struct snd_pcm_substream *substream,
> + struct snd_soc_dai *dai)
> +{
> + struct bcm2835_i2s_dev *dev = snd_soc_dai_get_drvdata(dai);
> +
> + bcm2835_i2s_stop(dev, substream, dai);
> +
> + /* If both streams are stopped, disable module and clock */
> + if (!dai->active) {
if (dai->active)
return;
> + /* Disable the module */
> + regmap_update_bits(dev->i2s_regmap, BCM2835_I2S_CS_A_REG,
> + BCM2835_I2S_EN, 0);
> +
> + /*
> + * Stopping clock is necessary, because stop does
> + * not stop the clock when SND_SOC_DAIFMT_CONT
> + */
> + bcm2835_i2s_stop_clock(dev);
> + }
> +}
> +
[]
> +static int bcm2835_i2s_probe(struct platform_device *pdev)
> +{
> + struct bcm2835_i2s_dev *dev;
> + int i;
> + int ret;
> + struct regmap *regmap[2];
> + struct resource *mem[2];
> +
> + /* Request both ioareas */
> + for (i = 0; i <= 1; i++) {
> + void __iomem *base;
> +
> + mem[i] = platform_get_resource(pdev, IORESOURCE_MEM, i);
> + if (!mem[i]) {
> + dev_err(&pdev->dev, "I2S probe: Memory resource could not be found.\n");
> + return -ENODEV;
> + }
Unneeded messaging and check.
> +
> + base = devm_ioremap_resource(&pdev->dev, mem[i]);
> + if (!base) {
It returns ERR_PTR.
Thus,
if (IS_ERR(base)
return PTR_ERR(base)
> + dev_err(&pdev->dev, "I2S probe: ioremap failed.\n");
Unneeded messaging.
> + return -ENOMEM;
Wrong error code. See above.
--
Andy Shevchenko <andriy.shevchenko@...el.com>
Intel Finland Oy
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