Re: [PATCH 03/10] ALSA: add AXD Audio Processing IP alsa driver

[Qais Yousef]

On 08/26/2015 07:37 PM, Mark Brown wrote:
> On Mon, Aug 24, 2015 at 01:39:12PM +0100, Qais Yousef wrote:
>
> > +#define THREAD_COUNT 4
> This is a very generic name that looks likely to collide with something
> else, please namespace.

OK.

> > +#define AXD_INPUT_DESCRIPTORS 10
> > +struct axd_input {
> > +	struct axd_buffer_desc descriptors[AXD_INPUT_DESCRIPTORS];
> > +};
> Where do these numbers come from?  Are they hardware limits or something
> else?

These numbers are what the firmware designed to work with. We had to set 
a limit and we sought 10 to be a good one for our purposes. We don't 
expect to need to change this number.

> > +/* this is required by MIPS ioremap_cachable() */
> > +#include <asm/pgtable.h>
> Don't work around this here, fix it in the relevant header.

Will do.

> > +#define AXD_BASE_VADDR		0xD0000000
> This sounds like something that is going to be platform dependant,
> should this be supplied from board configuration?

I don't expect this to change. Can we add the configuration later if we 
hit the need to change it?

> > +extern struct snd_compr_ops axd_compr_ops;
> Prototype shared definitions in headers not in C files please so we know
> the definition matches.

OK.

> > +static struct snd_soc_dai_driver axd_dai[] = {
> > +	{
> Why an array with only one entry?

Will fix it.

> > +	if (!*offp) {
> > +		unsigned int flags = axd_platform_lock();
> > +		unsigned int log_offset = ioread32(log_addr);
> > +		unsigned int log_wrapped = ioread32(log_addr + 8);
> > +		char __iomem *log_buff = (char __iomem *)(log_addr + 12);
> > +
> > +		/* new read from beginning, fill up our internal buffer */
> > +		if (!log_wrapped) {
> > +			memcpy_fromio(axd->log_rbuf, log_buff, log_offset);
> > +			axd->log_rbuf_rem = log_offset;
> > +		} else {
> > +			char __iomem *pos = log_buff + log_offset;
> > +			unsigned int rem = log_size - log_offset;
> > +
> > +			memcpy_fromio(axd->log_rbuf, pos, rem);
> > +			memcpy_fromio(axd->log_rbuf + rem, log_buff, log_offset);
> > +			axd->log_rbuf_rem = log_size;
> > +		}
> > +		axd_platform_unlock(flags);
> I didn't see the lock being taken?

The lock is the first line in the block (unsigned int flags = 
axd_platform_lock()). I'll tidy it up to make it more readable.

> > +static ssize_t axd_write_mask(struct file *filep,
> > +				const char __user *buff, size_t count, loff_t *offp)
> > +{
> > +	struct axd_dev *axd = filep->f_inode->i_private;
> > +	unsigned int mask;
> > +	char buffer[32] = {};
> > +	int ret;
> > +
> > +	/* ensure we always have null at the end */
> > +	ret = copy_from_user(buffer, buff, min(31u, count));
> > +	if (ret < 0)
> > +		return ret;
> > +
> > +	if (!kstrtouint(buffer, 0, &mask))
> > +		axd_write_reg(&axd->cmd, AXD_REG_DEBUG_MASK, mask);
> What are we writing here?  If we're going behind the driver's back on
> something that might confuse it it's generally better to taint the
> kernel so we know dodgy stuff happened later on.

The debug mask will cause AXD firmware to provide more or less debug 
information. We are not going behind the driver's back.

> > +static void axd_debugfs_create(struct axd_dev *axd)
> > +{
> > +	axd->debugfs = debugfs_create_dir(dev_name(axd->dev), NULL);
> > +	if (IS_ERR_OR_NULL(axd->debugfs)) {
> > +		dev_err(axd->dev, "failed to create debugfs node\n");
> > +		return;
> > +	}
> It'd be nicer to create this under the relevant ASoC debugfs directory
> so it's easier to find.

Sure. I'll try to find an example and follow what it does.

> > +#ifdef CONFIG_CRYPTO_LZO
> > +#include <linux/crypto.h>
> This include should be with all the other includes, not down here.

Was trying to reduce the ifdefery. Will fix.

> > +	size = axd->fw_size;
> > +	cached_fw_base = (char *)CAC_ADDR((int)axd->fw_base_m);
> > +	ret = crypto_comp_decompress(tfm, fw->data + 8,
> > +				fw->size - 8, cached_fw_base, &size);
> > +	if (ret)
> > +		dev_err(axd->dev, "Failed to decompress the firmware\n");
> Print return codes if you get them.

Will do.

> > +
> > +	if (size != axd->fw_size) {
> > +		dev_err(axd->dev, "Uncompressed file size doesn't match reported file size\n");
> > +		ret = -EINVAL;
> > +	}
> Should we be checking this if the decompression failed?

Nope. I'll fix it.

> > +}
> > +#else /* !CONFIG_CRYPTO_LZO */
> > +static int decompress_fw(struct axd_dev *axd, const struct firmware *fw)
> Blank lines between things please.

OK.

> > +{
> > +	dev_err(axd->dev, "The firmware must be lzo decompressed first, compile driver again with CONFIG_CRYPTO_LZO enabled in kernel or do the decompression in user space.\n");
> Please split this up into a few prints for wrapping, similarly in
> several other places.

OK. I thought the convention for strings to leave them as is to allow 
grepping. I'll fix it.

> > +	return -EIO;
> -ENOTSUPP.

OK.

> > +		return -EIO;
> > +	}
> > +	/*
> More vertical blanks missing.

OK.

> > +	 * We copy through the cache, fw will do the necessary cache
> > +	 * flushes and syncing at startup.
> > +	 * Copying from uncached makes it more difficult for the
> > +	 * firmware to keep the caches coherent with memory when it sets
> > +	 * tlbs and start running.
> > +	 */
> > +	memcpy_toio((void *)cached_fw_base, fw->data, fw->size);
> Why the cast here?  I'm also not seeing where we handled the copying to
> I/O in the decompression case?

I couldn't avoid the cast. If cached_fw_base is 'void *' I'll get a 
warning when initialising cached_fw_base from CAC_ADDR().
So I'll have to either cast here or there, I chose here.
If I pass axd->fw_base_m I encounter the issue described in the commit 
message.

Good point. When decompressing crypto_comp_decompress() will write 
directly to the memory. It is safe but it doesn't go through the correct 
API. Not sure what I can do here.

> > +	dev_info(axd->dev, "Loading firmware at 0x%p ...\n", axd->fw_base_m);
> This should be _dbg() at most, otherwise it's going to get noisy.
>
> > +	t0_new_pc = (unsigned long) axd->fw_base_m + (t0_new_pc - AXD_BASE_VADDR);
> Those casts look fishy...

I am happy to try something else. axd->fw_base_m is of type void * 
__iomem but we want to do some arithmetic on it.
Is there a better way to do it?

> > +	for (i = 0; i < AXD_LDFW_RETRIES; i++) {
> > +		ret = axd_wait_ready(axd_cmd->message);
> > +		if (!ret) {
> > +			/*
> > +			 * Let the firmware know the address of the buffer
> > +			 * region
> > +			 */
> > +			ret = axd_write_reg(axd_cmd,
> > +					AXD_REG_BUFFER_BASE, axd->buf_base_p);
> > +			if (ret) {
> > +				dev_err(axd->dev,
> > +					"Failed to setup buffers base address\n");
> Again print errors please.
>
> > +				goto out;
> > +			}
> > +			return 0;
> > +
> > +		}
> > +	}
> I'm not seeing any diagnostics if we fall out of the retry loop here?

Will add one.

> > +static void axd_reset(struct work_struct *work)
> > +{
> > +	unsigned int major, minor, patch;
> > +	int i;
> > +
> > +	struct axd_dev *axd = container_of(work, struct axd_dev, watchdogwork);
> > +
> > +
> > +	/* if we got a fatal error, don't reset if watchdog is disabled */
> > +	if (unlikely(!axd->cmd.watchdogenabled))
> > +		return;
> There's generally no need for unlikely() annotations outside of hot
> paths.

OK.

> > +	/* stop the watchdog timer until we restart */
> > +	del_timer(&axd->watchdogtimer);
> I'd expect del_timer_sync() to make sure that the timer stopped.

OK.

> > +	if (!axd_get_flag(&axd->cmd.fw_stopped_flg)) {
> > +		/* ping the firmware by requesting its version info */
> > +		axd_cmd_get_version(&axd->cmd, &major, &minor, &patch);
> > +		if (!major && !minor && !patch) {
> > +			dev_warn(axd->dev, "Firmware stopped responding...\n");
> > +			axd_set_flag(&axd->cmd.fw_stopped_flg, 1);
> > +		} else {
> > +			goto out;
> > +		}
> > +	}
> It might be useful to display the firmware version we loaded.

OK.

> > +	axd_platform_print_regs();
> > +	dev_warn(axd->dev, "Reloading AXD firmware...\n");
> This is going to get noisy and isn't adding much.

OK.

> > +	/* wake up any task sleeping on command response */
> > +	wake_up(&axd->cmd.wait);
> > +	/* give chance to user land tasks to react to the crash */
> > +	ssleep(2);
> This looks horribly racy, I'd expect us to be trashing and/or killing
> off any active work and resources here.

OK. I was trying to play nicely by giving the chance to userland to 
repond to -ERESTART which would be sent from aborting any pending 
reads/writes.

Are you suggesting to send SIGKILL using force_sig()?

> > +static void axd_watchdog_timer(unsigned long arg)
> > +{
> > +	struct axd_dev *axd = (struct axd_dev *)arg;
> > +
> > +	/* skip if watchdog is not enabled */
> > +	if (unlikely(!axd->cmd.watchdogenabled))
> > +		goto out;
> > +
> > +	schedule_work(&axd->watchdogwork);
> > +	return;
> > +out:
> > +	mod_timer(&axd->watchdogtimer, jiffies + WATCHDOG_TIMEOUT);
> > +}
> So we have a timer that just schedules some work?  Why not just
> schedule_delayed_work()?

Either wasn't there the time this was first written or was missed. 
Either case thanks for the suggestion I'll change it.

> > +	/*
> > +	 * Verify that the firmware is ready. In normal cases the firmware
> > +	 * should start immediately, but to be more robust we do this
> > +	 * verification and give the firmware a chance of 3 seconds to be ready
> > +	 * otherwise we exit in failure.
> > +	 */
> > +	for (i = 0; i < AXD_LDFW_RETRIES; i++) {
> > +		axd_cmd_get_version(&axd->cmd, &major, &minor, &patch);
> > +		if (major || minor || patch) {
> > +			/* firmware is ready */
> > +			break;
> > +		}
> > +		/* if we couldn't read the version after 3 tries, error */
> > +		if (i == AXD_LDFW_RETRIES - 1) {
> > +			dev_err(axd->dev, "Failed to communicate with the firmware\n");
> > +			ret = -EIO;
> > +			goto error;
> > +		}
> > +		/* wait for 10 ms for the firmware to start */
> > +		msleep(10);
> > +	}
> > +	dev_info(axd->dev, "Running firmware version %u.%u.%u %s\n",
> > +				major, minor, patch, axd_hdr_get_build_str());
> Why is this code not shared with the restart case?

I didn't think it's necessary but I see how it can be better to move it 
inside axd_fw_start() now.

> > +	ret = of_property_read_u32_array(of_node, "gic-irq", val, 2);
> > +	if (ret) {
> > +		dev_err(&pdev->dev,
> > +				"'gic-irq' parameter must be set\n");
> > +		return ret;
> > +	}
> This appears to have a DT binding but the binding is not documented.
> All new DT bindings must be documented.  I'm concerned that some of the
> properties being read from DT may not be ideal here...

It is documented on a different patch. Sorry I think I just added the DT 
maintainers to the CC for that patch and sent it to the ALSA list. I'll 
be more careful in the next series to include all ALSA maintainers for 
all patches.

Yes the DT will need to be enhanced. There's a separate discussion 
generated by one of the patches on this series about how IPI should be 
defined in DT.

See this

    https://lkml.org/lkml/2015/8/26/713

Again sorry for not explicitly adding you to the CC list for all the 
patches.

Thanks,
Qais

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