linux-kernel - [PATCH] spi: cadence-quadspi: Fix clock enable underflows due to runtime PM

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Message-Id: <20251202-spi-cadence-qspi-runtime-pm-imbalance-v1-1-aee8c7fa21f2@kernel.org>
Date: Tue, 02 Dec 2025 22:53:44 +0000
From: Mark Brown <broonie@...nel.org>
To: Francesco Dolcini <francesco@...cini.it>, 
 Siddharth Vadapalli <s-vadapalli@...com>, Anurag Dutta <a-dutta@...com>
Cc: linux-spi@...r.kernel.org, linux-kernel@...r.kernel.org, 
 Mark Brown <broonie@...nel.org>, stable@...r.kernel.org
Subject: [PATCH] spi: cadence-quadspi: Fix clock enable underflows due to
 runtime PM

The recent refactoring of where runtime PM is enabled done in commit
f1eb4e792bb1 ("spi: spi-cadence-quadspi: Enable pm runtime earlier to
avoid imbalance") made the fact that when we do a pm_runtime_disable()
in the error paths of probe() we can trigger a runtime disable which in
turn results in duplicate clock disables. Early on in the probe function
we do a pm_runtime_get_noresume() since the probe function leaves the
device in a powered up state but in the error path we can't assume that PM
is enabled so we also manually disable everything, including clocks. This
means that when runtime PM is active both it and the probe function release
the same reference to the main clock for the IP, triggering warnings from
the clock subsystem:

[    8.693719] clk:75:7 already disabled
[    8.693791] WARNING: CPU: 1 PID: 185 at /usr/src/kernel/drivers/clk/clk.c:1188 clk_core_disable+0xa0/0xb
...
[    8.694261]  clk_core_disable+0xa0/0xb4 (P)
[    8.694272]  clk_disable+0x38/0x60
[    8.694283]  cqspi_probe+0x7c8/0xc5c [spi_cadence_quadspi]
[    8.694309]  platform_probe+0x5c/0xa4

Avoid this confused ownership by moving the pm_runtime_get_noresume() to
after the last point at which the probe() function can fail.

Reported-by: Francesco Dolcini <francesco@...cini.it>
Closes: https://lore.kernel.org/r/20251201072844.GA6785@francesco-nb
Signed-off-by: Mark Brown <broonie@...nel.org>
Cc: stable@...r.kernel.org
---
 drivers/spi/spi-cadence-quadspi.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/spi/spi-cadence-quadspi.c b/drivers/spi/spi-cadence-quadspi.c
index af6d050da1c8..0833b6f666d0 100644
--- a/drivers/spi/spi-cadence-quadspi.c
+++ b/drivers/spi/spi-cadence-quadspi.c
@@ -1985,7 +1985,6 @@ static int cqspi_probe(struct platform_device *pdev)
 		pm_runtime_enable(dev);
 		pm_runtime_set_autosuspend_delay(dev, CQSPI_AUTOSUSPEND_TIMEOUT);
 		pm_runtime_use_autosuspend(dev);
-		pm_runtime_get_noresume(dev);
 	}

 	ret = cqspi_setup_flash(cqspi);
@@ -2012,6 +2011,7 @@ static int cqspi_probe(struct platform_device *pdev)
 	}

 	if (!(ddata && (ddata->quirks & CQSPI_DISABLE_RUNTIME_PM))) {
+		pm_runtime_get_noresume(dev);
 		pm_runtime_mark_last_busy(dev);
 		pm_runtime_put_autosuspend(dev);
 	}

---
base-commit: 7d0a66e4bb9081d75c82ec4957c50034cb0ea449
change-id: 20251202-spi-cadence-qspi-runtime-pm-imbalance-657740cf7eae

Best regards,
--  
Mark Brown <broonie@...nel.org>