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soundwire: stream: Poll for DP prepare to avoid interrupt deadlock

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Replace the wait_for_completion_timeout() in sdw_prep_deprep_slave_ports()
with a read_poll_timeout().

The original intent of the wait_for_completion_timeout() was to wait for
the port prepare interrupt. But at this time the code is holding the
bus_lock, which prevents the interrupt handler from running. Because of
this, the port_prep completion will not be signaled and the
wait_for_completion_timeout() will always timeout.

Rewriting the code to avoid taking the bus_lock carries risks, and
needs careful consideration of the consequences. It is safer and simpler
to replace the completion with a simple register poll.

As the code is holding the bus_lock, it is already blocking other activity
so consuming control channel bandwidth for polling isn't really a concern.

Signed-off-by: Richard Fitzgerald <rf@opensource.cirrus.com>
Link: https://patch.msgid.link/20260227111648.175548-1-rf@opensource.cirrus.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>
This commit is contained in:
Richard Fitzgerald 2026-02-27 11:16:48 +00:00 committed by Vinod Koul
parent 27ab4f1e49
commit fee12f3c20
1 changed files with 14 additions and 8 deletions
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22
drivers/soundwire/stream.c
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@ -8,6 +8,7 @@
#include <linux/delay.h>
#include <linux/device.h>
#include <linux/init.h>
#include <linux/iopoll.h>
#include <linux/module.h>
#include <linux/mod_devicetable.h>
#include <linux/slab.h>
@ -18,6 +19,8 @@
#include <sound/soc.h>
#include "bus.h"
#define SDW_PORT_PREP_POLL_USEC 1000
/*
* Array of supported rows and columns as per MIPI SoundWire Specification 1.1
*
@ -443,7 +446,6 @@ static int sdw_prep_deprep_slave_ports(struct sdw_bus *bus,
struct sdw_port_runtime *p_rt,
bool prep)
{
struct completion *port_ready;
struct sdw_dpn_prop *dpn_prop;
struct sdw_prepare_ch prep_ch;
u32 imp_def_interrupts;
@ -518,14 +520,18 @@ static int sdw_prep_deprep_slave_ports(struct sdw_bus *bus,
return ret;
}
/* Wait for completion on port ready */
port_ready = &s_rt->slave->port_ready[prep_ch.num];
wait_for_completion_timeout(port_ready,
msecs_to_jiffies(ch_prep_timeout));
/*
* Poll for NOT_PREPARED==0. Cannot use the interrupt because
* this code holds bus_lock which blocks interrupt handling.
*/
ret = read_poll_timeout(sdw_read_no_pm, val,
(val < 0) || ((val & p_rt->ch_mask) == 0),
SDW_PORT_PREP_POLL_USEC, ch_prep_timeout * USEC_PER_MSEC,
false, s_rt->slave, SDW_DPN_PREPARESTATUS(p_rt->num));
if (ret || (val < 0)) {
if (val < 0)
ret = val;
val = sdw_read_no_pm(s_rt->slave, SDW_DPN_PREPARESTATUS(p_rt->num));
if ((val < 0) || (val & p_rt->ch_mask)) {
ret = (val < 0) ? val : -ETIMEDOUT;
dev_err(&s_rt->slave->dev,
"Chn prep failed for port %d: %d\n", prep_ch.num, ret);
return ret;