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spi: cadence-qspi: remove system-wide suspend helper calls from runtime PM hooks

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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: 0578a6dbfe ("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>
This commit is contained in:
Théo Lebrun 2024-02-22 11:12:30 +01:00 committed by Mark Brown
parent 32ce3bb57b
commit 959043afe5
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GPG key ID: 24D68B725D5487D0
1 changed files with 2 additions and 7 deletions
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9
drivers/spi/spi-cadence-quadspi.c
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@ -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,