From bff89e900149a1684255adf7469862b35dafc037 Mon Sep 17 00:00:00 2001 From: Richard Fitzgerald Date: Tue, 23 Dec 2025 15:28:59 +0000 Subject: [PATCH] soundwire: stream: Poll for DP prepare to avoid interrupt deadlock 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_pre 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 --- drivers/soundwire/stream.c | 22 +++++++++++++--------- 1 file changed, 13 insertions(+), 9 deletions(-) diff --git a/drivers/soundwire/stream.c b/drivers/soundwire/stream.c index 66ec70930d77ca..aa8f31b53d778d 100644 --- a/drivers/soundwire/stream.c +++ b/drivers/soundwire/stream.c @@ -8,6 +8,7 @@ #include #include #include +#include #include #include #include @@ -26,6 +27,8 @@ static int p_lane; module_param(p_lane, int, 0444); MODULE_PARM_DESC(p_lane, "Peripheral lane"); +#define SDW_PORT_PREP_POLL_USEC 1000 + /* * Array of supported rows and columns as per MIPI SoundWire Specification 1.1 * @@ -451,7 +454,6 @@ 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; @@ -492,7 +494,7 @@ static int sdw_prep_deprep_slave_ports(struct sdw_bus *bus, prep_ch.bank = bus->params.next_bank; - if (imp_def_interrupts || !simple_ch_prep_sm || + if (imp_def_interrupts || bus->params.s_data_mode != SDW_PORT_DATA_MODE_NORMAL) intr = true; @@ -526,13 +528,15 @@ 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)); - - val = sdw_read_no_pm(s_rt->slave, SDW_DPN_PREPARESTATUS(p_rt->num)); - if ((val < 0) || (val & p_rt->ch_mask)) { + /* + * Poll for NOT_PREPARED. 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) || (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);