Re: [Alsa-devel] [PATCH] Add Dreamcast AICA driver to alsa-driver

[Takashi Iwai]

At Sun, 23 Apr 2006 23:46:22 +0100,
Adrian McMenamin wrote:
+/* module parameters */
+#define CARD_NAME "AICA"
+
+static int index;

Initialize it to -1 (or SNDRV_DEFAULT_IDX1), and pass it to the first
argument of snd_card_new().  Otherwise this option is useless.


> +/* Spinlocks */
> +DEFINE_SPINLOCK(spu_memlock);

Missing static.


> +/* spu_memset - write to memory in SPU address space */
> +static void spu_memset(uint32_t toi, void __iomem * what, int length)
> +{
> +	uint32_t *to = (uint32_t *) (SPU_MEMORY_BASE + toi);
> +	int i;
> +	if (length % 4)
> +		length = (length / 4) + 1;
> +	else
> +		length = length / 4;

If you use writel(), the length must be aligned to 4.


> +	spu_write_wait();
> +	for (i = 0; i < length; i++) {
> +		spin_lock(&spu_memlock);
> +		writel(what, to);
> +		spin_unlock(&spu_memlock);

What's the purpose of this lock?


> +		to++;
> +		if (i && !(i % 8))
> +			spu_write_wait();
> +	}
> +}
> +
> +/* spu_memload - write to SPU address space */
> +static void spu_memload(uint32_t toi, void __iomem * from, int length)
> +{
> +	uint32_t __iomem *froml = from;
> +	uint32_t __iomem *to =
> +	    (uint32_t __iomem *) (SPU_MEMORY_BASE + toi);
> +	int i, val;
> +	if (length % 4)
> +		length = (length / 4) + 1;
> +	else
> +		length = length / 4;

Ditto.


> +/* spu_disable - set spu registers to stop sound output */
> +static void spu_disable(void)
> +{
> +	int i;
> +	uint32_t regval;
> +	spu_write_wait();
> +	regval = readl(ARM_RESET_REGISTER);
> +	regval |= 1;
> +	spu_write_wait();
> +	spin_lock(&spu_memlock);
> +	writel(regval, ARM_RESET_REGISTER);
> +	spin_unlock(&spu_memlock);
> +	for (i = 0; i < 64; i++) {
> +		spu_write_wait();
> +		regval = readl(SPU_REGISTER_BASE + (i * 0x80));
> +		regval = (regval & ~0x4000) | 0x8000;
> +		spu_write_wait();
> +		spin_lock(&spu_memlock);
> +		writel(regval, SPU_REGISTER_BASE + (i * 0x80));
> +		spin_unlock(&spu_memlock);

For what is this lock?


> +/* aica_chn_start - write to spu to start playback */
> +inline static void aica_chn_start(void)
> +{
> +	spu_write_wait();
> +	spin_lock(&spu_memlock);
> +	writel(AICA_CMD_KICK | AICA_CMD_START,
> +	       (uint32_t *) AICA_CONTROL_POINT);

The cast looks strange...


> +	spin_unlock(&spu_memlock);
> +}
> +
> +/* aica_chn_halt - write to spu to halt playback */
> +inline static void aica_chn_halt(void)
> +{
> +	spu_write_wait();
> +	spin_lock(&spu_memlock);
> +	writel(AICA_CMD_KICK | AICA_CMD_STOP,
> +	       (uint32_t *) AICA_CONTROL_POINT);
> +	spin_unlock(&spu_memlock);
> +}
> +
> +/* ALSA code below */
> +static struct snd_pcm_hardware snd_pcm_aica_playback_hw = {
> +	.info = (SNDRV_PCM_INFO_NONINTERLEAVED),.formats =
> +	    (SNDRV_PCM_FMTBIT_S8 | SNDRV_PCM_FMTBIT_S16_LE |
> +	     SNDRV_PCM_FMTBIT_IMA_ADPCM),.rates =
> +	    SNDRV_PCM_RATE_8000_48000,.rate_min = 8000,.rate_max =
> +	    48000,.channels_min = 1,.channels_max = 2,.buffer_bytes_max =
> +	    AICA_BUFFER_SIZE,.period_bytes_min =
> +	    AICA_PERIOD_SIZE,.period_bytes_max =
> +	    AICA_PERIOD_SIZE,.periods_min =
> +	    AICA_PERIOD_NUMBER,.periods_max = AICA_PERIOD_NUMBER,
> +};

Put the field ids to the beginning of the line.  Found in other
structs, too.


> +static int stereo_buffer_transfer(struct snd_pcm_substream
> +				  *substream, int buffer_size, int period)
> +{

I feel this transfer-and-wait could be done more efficiently using
workq than doing it in timer callback.  The trigger(start) and
aica_period_elapsed() calls queue_work() at each time.

The most work of spu_begin_dma() should be put in the workq, too.


> +	int transferred;
> +	int dma_countout;
> +	struct snd_pcm_runtime *runtime;
> +	int period_offset;
> +	long dma_flags;
> +	period_offset = period;
> +	period_offset %= (AICA_PERIOD_NUMBER / 2);
> +	runtime = substream->runtime;
> +	/* transfer left and then right */
> +	dma_flags = claim_dma_lock();
> +	dma_countout = 0;
> +	dma_xfer(0,
> +		 runtime->dma_area + (AICA_PERIOD_SIZE * period_offset),
> +		 AICA_CHANNEL0_OFFSET +
> +		 (AICA_PERIOD_SIZE * period_offset), buffer_size / 2, 5);
> +	/* wait for completion */
> +	do {
> +		udelay(5);
> +		transferred = get_dma_residue(0);
> +		dma_countout++;
> +		if (dma_countout > 0x10000)
> +			break;	/* Approx 1/3 sec timeout in case of hardware failure */
> +	}
> +	while (transferred < buffer_size / 2);
> +	dma_xfer(0,
> +		 AICA_BUFFER_SIZE / 2 + runtime->dma_area +
> +		 (AICA_PERIOD_SIZE * period_offset),
> +		 AICA_CHANNEL1_OFFSET +
> +		 (AICA_PERIOD_SIZE * period_offset), buffer_size / 2, 5);
> +	/* have to wait again */
> +	dma_countout = 0;
> +	do {
> +		udelay(5);
> +		transferred = get_dma_residue(0);
> +		dma_countout++;
> +		if (dma_countout > 0x10000)
> +			break;
> +	}
> +	while (transferred < buffer_size / 2);
> +	release_dma_lock(dma_flags);
> +	return 0;
> +}

You can write a single function for both mono and two-channel
streams.


> +static int snd_aicapcm_pcm_open(struct snd_pcm_substream
> +				*substream)
> +{
> +	struct snd_pcm_runtime *runtime;
> +	struct aica_channel *channel;
> +	struct snd_card_aica *dreamcastcard;
> +	if (!enable)
> +		return -ENOENT;

You don't need to check enable here.

The "enable" module option was introduced to enable/disable the
speicfic device when multiple same devices are on the system.  Hence
it makes no sense for the drivers that support only a single device.
But we keep this option as a dummy one in most of drivers just for
compatibility reason.  The sound configurator tends to set this option
unconditionally.


> +/* TO DO: set up to handle more than one pcm instance */
> +static int __init snd_aicapcmchip(struct snd_card_aica
> +				  *dreamcastcard, int pcm_index)

Use __devinit prefix as long as you use platform_driver.


> +static int remove_dreamcastcard(struct device *dreamcast_device)
> +{
> +	struct snd_card_aica *dreamcastcard =
> +	    dreamcast_device->driver_data;
> +	snd_card_free(dreamcastcard->card);
> +	kfree(dreamcastcard);
> +	return 0;
> +}
> +
> +static struct device_driver aica_driver = {
> +	.name = "AICA",.bus = &platform_bus_type,
> +	.remove = remove_dreamcastcard,
> +};

Any reason not to use struct platform_driver?


> +static int load_aica_firmware()
> +{
> +	int err;
> +	err = 0;
> +	spu_init();
> +	const struct firmware *fw_entry;

The variable definition must be in the beginning of the function
block.


> +static int __init aica_init(void)
> +{
> +	int err;
> +	struct snd_card_aica *dreamcastcard;
> +	/* Are we in a Dreamcast at all? */
> +	if (!mach_is_dreamcast())
> +		return -ENODEV;

The typical flow in init entry should be:

	- register platform_driver
	- register platform_device	
	  -> initialize the card and releveant instances in probe
	     callback


BTW, with the latest HG repo, you can add alsa-driver/Kconfig, so that
you can keep alsa-kernel tree intact.


Takashi
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