[PATCH 6.7 009/162] spi: cadence-qspi: remove system-wide suspend helper calls from runtime PM hooks

Greg Kroah-Hartman
2024-03-04T21:26:37Z

From: Théo Lebrun <theo.lebrun@bootlin.com>

[ Upstream commit 959043afe53ae80633e810416cee6076da6e91c6 ]

The ->runtime_suspend() and ->runtime_resume() callbacks are not
expected to call spi_controller_suspend() and spi_controller_resume().
Remove calls to those in the cadence-qspi driver.

Those helpers have two roles currently:
- They stop/start the queue, including dealing with the kworker.
- They toggle the SPI controller SPI_CONTROLLER_SUSPENDED flag. It
requires acquiring ctlr->bus_lock_mutex.

Step one is irrelevant because cadence-qspi is not queued. Step two
however has two implications:
- A deadlock occurs, because ->runtime_resume() is called in a context
where the lock is already taken (in the ->exec_op() callback, where
the usage count is incremented).
- It would disallow all operations once the device is auto-suspended.

Here is a brief call tree highlighting the mutex deadlock:

spi_mem_exec_op()
...
spi_mem_access_start()
mutex_lock(&ctlr->bus_lock_mutex)

cqspi_exec_mem_op()
pm_runtime_resume_and_get()
cqspi_resume()
spi_controller_resume()
mutex_lock(&ctlr->bus_lock_mutex)
...

spi_mem_access_end()
mutex_unlock(&ctlr->bus_lock_mutex)
...

Fixes: 0578a6dbfe75 ("spi: spi-cadence-quadspi: add runtime pm support")
Signed-off-by: Théo Lebrun <theo.lebrun@bootlin.com>
Link: https://msgid.link/r/20240222-cdns-qspi-pm-fix-v4-2-6b6af8bcbf59@bootlin.com
Signed-off-by: Mark Brown <broonie@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/spi/spi-cadence-quadspi.c | 9 ++-------
1 file changed, 2 insertions(+), 7 deletions(-)

diff --git a/drivers/spi/spi-cadence-quadspi.c b/drivers/spi/spi-cadence-quadspi.c
index 0d184d65dce76..731775d34d393 100644
--- a/drivers/spi/spi-cadence-quadspi.c
+++ b/drivers/spi/spi-cadence-quadspi.c
@@ -1930,14 +1930,10 @@ static void cqspi_remove(struct platform_device *pdev)
static int cqspi_suspend(struct device *dev)
{
struct cqspi_st *cqspi = dev_get_drvdata(dev);
- int ret;

- ret = spi_controller_suspend(cqspi->host);
cqspi_controller_enable(cqspi, 0);
-
clk_disable_unprepare(cqspi->clk);
-
- return ret;
+ return 0;
}

static int cqspi_resume(struct device *dev)
@@ -1950,8 +1946,7 @@ static int cqspi_resume(struct device *dev)

cqspi->current_cs = -1;
cqspi->sclk = 0;
-
- return spi_controller_resume(cqspi->host);
+ return 0;
}

static DEFINE_RUNTIME_DEV_PM_OPS(cqspi_dev_pm_ops, cqspi_suspend,
--
2.43.0