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Message-Id: <20240209-cdns-qspi-pm-fix-v3-2-540ac222f26b@bootlin.com>
Date: Fri, 09 Feb 2024 14:55:51 +0100
From: Théo Lebrun <theo.lebrun@...tlin.com>
To: Mark Brown <broonie@...nel.org>, Apurva Nandan <a-nandan@...com>,
Dhruva Gole <d-gole@...com>
Cc: linux-spi@...r.kernel.org, linux-kernel@...r.kernel.org,
Gregory CLEMENT <gregory.clement@...tlin.com>,
Vladimir Kondratiev <vladimir.kondratiev@...ileye.com>,
Thomas Petazzoni <thomas.petazzoni@...tlin.com>,
Tawfik Bayouk <tawfik.bayouk@...ileye.com>,
Théo Lebrun <theo.lebrun@...tlin.com>
Subject: [PATCH v3 2/4] spi: cadence-qspi: remove system-wide suspend
helper calls from runtime PM hooks
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@...tlin.com>
---
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 d19ba024c80b..809bbbb876ad 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
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