/*
 * linux/kernel/dma.c: A DMA channel allocator. Inspired by linux/kernel/irq.c.
 *
 * Written by Hennus Bergman, 1992.
 *
 * 1994/12/26: Changes by Alex Nash to fix a minor bug in /proc/dma.
 *   In the previous version the reported device could end up being wrong,
 *   if a device requested a DMA channel that was already in use.
 *   [It also happened to remove the sizeof(char *) == sizeof(int)
 *   assumption introduced because of those /proc/dma patches. -- Hennus]
 */
#include <linux/export.h>
#include <linux/kernel.h>
#include <linux/errno.h>
#include <linux/spinlock.h>
#include <linux/string.h>
#include <linux/seq_file.h>
#include <linux/proc_fs.h>
#include <linux/init.h>
#include <asm/dma.h>



/* A note on resource allocation:
 *
 * All drivers needing DMA channels, should allocate and release them
 * through the public routines `request_dma()' and `free_dma()'.
 *
 * In order to avoid problems, all processes should allocate resources in
 * the same sequence and release them in the reverse order.
 *
 * So, when allocating DMAs and IRQs, first allocate the IRQ, then the DMA.
 * When releasing them, first release the DMA, then release the IRQ.
 * If you don't, you may cause allocation requests to fail unnecessarily.
 * This doesn't really matter now, but it will once we get real semaphores
 * in the kernel.
 */


DEFINE_SPINLOCK(dma_spin_lock);

/*
 *	If our port doesn't define this it has no PC like DMA
 */

#ifdef MAX_DMA_CHANNELS


/* Channel n is busy iff dma_chan_busy[n].lock != 0.
 * DMA0 used to be reserved for DRAM refresh, but apparently not any more...
 * DMA4 is reserved for cascading.
 */

struct dma_chan {
	int  lock;
	const char *device_id;
};

static struct dma_chan dma_chan_busy[MAX_DMA_CHANNELS] = {
	[4] = { 1, "cascade" },
};


/**
 * request_dma - request and reserve a system DMA channel
 * @dmanr: DMA channel number
 * @device_id: reserving device ID string, used in /proc/dma
 */
int request_dma(unsigned int dmanr, const char * device_id)
{
	if (dmanr >= MAX_DMA_CHANNELS)
		return -EINVAL;

	if (xchg(&dma_chan_busy[dmanr].lock, 1) != 0)
		return -EBUSY;

	dma_chan_busy[dmanr].device_id = device_id;

	/* old flag was 0, now contains 1 to indicate busy */
	return 0;
} /* request_dma */

/**
 * free_dma - free a reserved system DMA channel
 * @dmanr: DMA channel number
 */
void free_dma(unsigned int dmanr)
{
	if (dmanr >= MAX_DMA_CHANNELS) {
		printk(KERN_WARNING "Trying to free DMA%d\n", dmanr);
		return;
	}

	if (xchg(&dma_chan_busy[dmanr].lock, 0) == 0) {
		printk(KERN_WARNING "Trying to free free DMA%d\n", dmanr);
		return;
	}

} /* free_dma */

#else

int request_dma(unsigned int dmanr, const char *device_id)
{
	return -EINVAL;
}

void free_dma(unsigned int dmanr)
{
}

#endif

#ifdef CONFIG_PROC_FS

#ifdef MAX_DMA_CHANNELS
static int proc_dma_show(struct seq_file *m, void *v)
{
	int i;

	for (i = 0 ; i < MAX_DMA_CHANNELS ; i++) {
		if (dma_chan_busy[i].lock) {
			seq_printf(m, "%2d: %s\n", i,
				   dma_chan_busy[i].device_id);
		}
	}
	return 0;
}
#else
static int proc_dma_show(struct seq_file *m, void *v)
{
	seq_puts(m, "No DMA\n");
	return 0;
}
#endif /* MAX_DMA_CHANNELS */

static int proc_dma_open(struct inode *inode, struct file *file)
{
	return single_open(file, proc_dma_show, NULL);
}

static const struct file_operations proc_dma_operations = {
	.open		= proc_dma_open,
	.read		= seq_read,
	.llseek		= seq_lseek,
	.release	= single_release,
};

static int __init proc_dma_init(void)
{
	proc_create("dma", 0, NULL, &proc_dma_operations);
	return 0;
}

__initcall(proc_dma_init);
#endif

EXPORT_SYMBOL(request_dma);
EXPORT_SYMBOL(free_dma);
EXPORT_SYMBOL(dma_spin_lock);
nel'><b>diff options</b><form method='get'><input type='hidden' name='h' value='nds-private-remove'/><input type='hidden' name='id' value='ae4a3e028bb8b59e7cfeb0cc9ef03d885182ce8b'/><table><tr><td colspan='2'/></tr><tr><td class='label'>context:</td><td class='ctrl'><select name='context' onchange='this.form.submit();'><option value='1'>1</option><option value='2'>2</option><option value='3' selected='selected'>3</option><option value='4'>4</option><option value='5'>5</option><option value='6'>6</option><option value='7'>7</option><option value='8'>8</option><option value='9'>9</option><option value='10'>10</option><option value='15'>15</option><option value='20'>20</option><option value='25'>25</option><option value='30'>30</option><option value='35'>35</option><option value='40'>40</option></select></td></tr><tr><td class='label'>space:</td><td class='ctrl'><select name='ignorews' onchange='this.form.submit();'><option value='0' selected='selected'>include</option><option value='1'>ignore</option></select></td></tr><tr><td class='label'>mode:</td><td class='ctrl'><select name='dt' onchange='this.form.submit();'><option value='0' selected='selected'>unified</option><option value='1'>ssdiff</option><option value='2'>stat only</option></select></td></tr><tr><td/><td class='ctrl'><noscript><input type='submit' value='reload'/></noscript></td></tr></table></form></div><table summary='commit info' class='commit-info'>
<tr><th>author</th><td>Tony Lindgren &lt;tony@atomide.com&gt;</td><td class='right'>2017-01-19 08:49:07 -0800</td></tr>
<tr><th>committer</th><td>Vinod Koul &lt;vinod.koul@intel.com&gt;</td><td class='right'>2017-01-25 11:29:11 +0530</td></tr>
<tr><th>commit</th><td colspan='2' class='oid'><a href='/cgit.cgi/linux/net-next.git/commit/sound/usb/line6/variax.c?h=nds-private-remove&amp;id=ae4a3e028bb8b59e7cfeb0cc9ef03d885182ce8b'>ae4a3e028bb8b59e7cfeb0cc9ef03d885182ce8b</a> (<a href='/cgit.cgi/linux/net-next.git/patch/sound/usb/line6/variax.c?id=ae4a3e028bb8b59e7cfeb0cc9ef03d885182ce8b'>patch</a>)</td></tr>
<tr><th>tree</th><td colspan='2' class='oid'><a href='/cgit.cgi/linux/net-next.git/tree/?h=nds-private-remove&amp;id=ae4a3e028bb8b59e7cfeb0cc9ef03d885182ce8b'>139fc7e29f97d6bb6c4dca2a97be2dc3f824bd51</a> /<a href='/cgit.cgi/linux/net-next.git/tree/sound/usb/line6/variax.c?h=nds-private-remove&amp;id=ae4a3e028bb8b59e7cfeb0cc9ef03d885182ce8b'>sound/usb/line6/variax.c</a></td></tr>
<tr><th>parent</th><td colspan='2' class='oid'><a href='/cgit.cgi/linux/net-next.git/commit/sound/usb/line6/variax.c?h=nds-private-remove&amp;id=49def1853334396f948dcb4cedb9347abb318df5'>49def1853334396f948dcb4cedb9347abb318df5</a> (<a href='/cgit.cgi/linux/net-next.git/diff/sound/usb/line6/variax.c?h=nds-private-remove&amp;id=ae4a3e028bb8b59e7cfeb0cc9ef03d885182ce8b&amp;id2=49def1853334396f948dcb4cedb9347abb318df5'>diff</a>)</td></tr></table>
<div class='commit-subject'>dmaengine: cppi41: Fix runtime PM timeouts with USB mass storage</div><div class='commit-msg'>Commit fdea2d09b997 ("dmaengine: cppi41: Add basic PM runtime support")
added runtime PM support for cppi41, but had corner case issues. Some of
the issues were fixed with commit 098de42ad670 ("dmaengine: cppi41: Fix
unpaired pm runtime when only a USB hub is connected"). That fix however
caused a new regression where we can get error -115 messages with USB on
BeagleBone when connecting a USB mass storage device to a hub.

This is because when connecting a USB mass storage device to a hub, the
initial DMA transfers can take over 200ms to complete and cppi41
autosuspend delay times out.

To fix the issue, we want to implement refcounting for chan_busy array
that contains the active dma transfers. Increasing the autosuspend delay
won't help as that the delay could be potentially seconds, and it's best
to let the USB subsystem to deal with the timeouts on errors.

The earlier attempt for runtime PM was buggy as the pm_runtime_get/put()
calls could get unpaired easily as they did not follow the state of
the chan_busy array as described in commit 098de42ad670 ("dmaengine:
cppi41: Fix unpaired pm runtime when only a USB hub is connected".

Let's fix the issue by adding pm_runtime_get() to where a new transfer
is added to the chan_busy array, and calls to pm_runtime_put() where
chan_busy array entry is cleared. This prevents any autosuspend timeouts
from happening while dma transfers are active.

Fixes: 098de42ad670 ("dmaengine: cppi41: Fix unpaired pm runtime when
only a USB hub is connected")
Fixes: fdea2d09b997 ("dmaengine: cppi41: Add basic PM runtime support")
Cc: Andy Shevchenko &lt;andy.shevchenko@gmail.com&gt;
Cc: Bin Liu &lt;b-liu@ti.com&gt;
Cc: Grygorii Strashko &lt;grygorii.strashko@ti.com&gt;
Cc: Kevin Hilman &lt;khilman@baylibre.com&gt;
Cc: Patrick Titiano &lt;ptitiano@baylibre.com&gt;
Cc: Sergei Shtylyov &lt;sergei.shtylyov@cogentembedded.com&gt;
Signed-off-by: Tony Lindgren &lt;tony@atomide.com&gt;
Tested-by: Bin Liu &lt;b-liu@ti.com&gt;
Signed-off-by: Vinod Koul &lt;vinod.koul@intel.com&gt;
</div><div class='diffstat-header'><a href='/cgit.cgi/linux/net-next.git/diff/?h=nds-private-remove&amp;id=ae4a3e028bb8b59e7cfeb0cc9ef03d885182ce8b'>Diffstat</a> (limited to 'sound/usb/line6/variax.c')</div><table summary='diffstat' class='diffstat'>