/*
 * linux/net/sunrpc/timer.c
 *
 * Estimate RPC request round trip time.
 *
 * Based on packet round-trip and variance estimator algorithms described
 * in appendix A of "Congestion Avoidance and Control" by Van Jacobson
 * and Michael J. Karels (ACM Computer Communication Review; Proceedings
 * of the Sigcomm '88 Symposium in Stanford, CA, August, 1988).
 *
 * This RTT estimator is used only for RPC over datagram protocols.
 *
 * Copyright (C) 2002 Trond Myklebust <trond.myklebust@fys.uio.no>
 */

#include <asm/param.h>

#include <linux/types.h>
#include <linux/unistd.h>
#include <linux/module.h>

#include <linux/sunrpc/clnt.h>

#define RPC_RTO_MAX (60*HZ)
#define RPC_RTO_INIT (HZ/5)
#define RPC_RTO_MIN (HZ/10)

/**
 * rpc_init_rtt - Initialize an RPC RTT estimator context
 * @rt: context to initialize
 * @timeo: initial timeout value, in jiffies
 *
 */
void rpc_init_rtt(struct rpc_rtt *rt, unsigned long timeo)
{
	unsigned long init = 0;
	unsigned int i;

	rt->timeo = timeo;

	if (timeo > RPC_RTO_INIT)
		init = (timeo - RPC_RTO_INIT) << 3;
	for (i = 0; i < 5; i++) {
		rt->srtt[i] = init;
		rt->sdrtt[i] = RPC_RTO_INIT;
		rt->ntimeouts[i] = 0;
	}
}
EXPORT_SYMBOL_GPL(rpc_init_rtt);

/**
 * rpc_update_rtt - Update an RPC RTT estimator context
 * @rt: context to update
 * @timer: timer array index (request type)
 * @m: recent actual RTT, in jiffies
 *
 * NB: When computing the smoothed RTT and standard deviation,
 *     be careful not to produce negative intermediate results.
 */
void rpc_update_rtt(struct rpc_rtt *rt, unsigned int timer, long m)
{
	long *srtt, *sdrtt;

	if (timer-- == 0)
		return;

	/* jiffies wrapped; ignore this one */
	if (m < 0)
		return;

	if (m == 0)
		m = 1L;

	srtt = (long *)&rt->srtt[timer];
	m -= *srtt >> 3;
	*srtt += m;

	if (m < 0)
		m = -m;

	sdrtt = (long *)&rt->sdrtt[timer];
	m -= *sdrtt >> 2;
	*sdrtt += m;

	/* Set lower bound on the variance */
	if (*sdrtt < RPC_RTO_MIN)
		*sdrtt = RPC_RTO_MIN;
}
EXPORT_SYMBOL_GPL(rpc_update_rtt);

/**
 * rpc_calc_rto - Provide an estimated timeout value
 * @rt: context to use for calculation
 * @timer: timer array index (request type)
 *
 * Estimate RTO for an NFS RPC sent via an unreliable datagram.  Use
 * the mean and mean deviation of RTT for the appropriate type of RPC
 * for frequently issued RPCs, and a fixed default for the others.
 *
 * The justification for doing "other" this way is that these RPCs
 * happen so infrequently that timer estimation would probably be
 * stale.  Also, since many of these RPCs are non-idempotent, a
 * conservative timeout is desired.
 *
 * getattr, lookup,
 * read, write, commit     - A+4D
 * other                   - timeo
 */
unsigned long rpc_calc_rto(struct rpc_rtt *rt, unsigned int timer)
{
	unsigned long res;

	if (timer-- == 0)
		return rt->timeo;

	res = ((rt->srtt[timer] + 7) >> 3) + rt->sdrtt[timer];
	if (res > RPC_RTO_MAX)
		res = RPC_RTO_MAX;

	return res;
}
EXPORT_SYMBOL_GPL(rpc_calc_rto);
8b'>openvswitch</a></div><div class='content'><div class='cgit-panel'><b>diff options</b><form method='get'><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/net/openvswitch?id=ae4a3e028bb8b59e7cfeb0cc9ef03d885182ce8b'>ae4a3e028bb8b59e7cfeb0cc9ef03d885182ce8b</a> (<a href='/cgit.cgi/linux/net-next.git/patch/net/openvswitch?id=ae4a3e028bb8b59e7cfeb0cc9ef03d885182ce8b'>patch</a>)</td></tr>
<tr><th>tree</th><td colspan='2' class='oid'><a href='/cgit.cgi/linux/net-next.git/tree/?id=ae4a3e028bb8b59e7cfeb0cc9ef03d885182ce8b'>139fc7e29f97d6bb6c4dca2a97be2dc3f824bd51</a> /<a href='/cgit.cgi/linux/net-next.git/tree/net/openvswitch?id=ae4a3e028bb8b59e7cfeb0cc9ef03d885182ce8b'>net/openvswitch</a></td></tr>
<tr><th>parent</th><td colspan='2' class='oid'><a href='/cgit.cgi/linux/net-next.git/commit/net/openvswitch?id=49def1853334396f948dcb4cedb9347abb318df5'>49def1853334396f948dcb4cedb9347abb318df5</a> (<a href='/cgit.cgi/linux/net-next.git/diff/net/openvswitch?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/?id=ae4a3e028bb8b59e7cfeb0cc9ef03d885182ce8b'>Diffstat</a> (limited to 'net/openvswitch')</div><table summary='diffstat' class='diffstat'>