spi: cadence-qspi: remove system-wide suspend helper calls from runtime PM hookstoradex_ti-linux-6.1.y

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)
        ...

Upstream-Status: Backport [959043afe53ae80633e810416cee6076da6e91c6]
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>

1 files changed, 2 insertions, 6 deletions

diff --git a/drivers/spi/spi-cadence-quadspi.c b/drivers/spi/spi-cadence-quadspi.c
index c34a432af4f0..9e91686c7c96 100644
--- a/drivers/spi/spi-cadence-quadspi.c
+++ b/drivers/spi/spi-cadence-quadspi.c
@@ -2675,14 +2675,10 @@ static void __maybe_unused cqspi_restore_context(struct cqspi_st *cqspi)
 static int cqspi_suspend(struct device *dev)
 {
 	struct cqspi_st *cqspi = dev_get_drvdata(dev);
-	int ret;
 
-	ret = spi_master_suspend(cqspi->master);
 	cqspi_controller_enable(cqspi, 0);
-
 	clk_disable_unprepare(cqspi->clk);
-
-	return ret;
+	return 0;
 }
 
 static int cqspi_resume(struct device *dev)
@@ -2702,7 +2698,7 @@ static int cqspi_resume(struct device *dev)
 	if ((cqspi->f_pdata->use_phy) == true)
 		cqspi_restore_context(cqspi);
 
-	return spi_master_resume(cqspi->master);
+	return 0;
 }
 
 static DEFINE_RUNTIME_DEV_PM_OPS(cqspi_dev_pm_ops, cqspi_suspend,