[PATCH 2/2] spi: fsl-qspi: Explicitly unregister SPI host in remove()

[Kevin Hao <haokexin@gmail.com>]

Currently, the SPI host is registered using a managed API, which
automatically unregisters it when the device is detached from its driver.
However, this unregistration occurs after the driver's remove() callback.

Since the host is already disabled inside the remove(), any pending IO
from child devices can easily corrupt the kernel.

For example, the following steps on an imx8mq-evk board can trigger a
kernel panic:
  while true; do cat /dev/mtd0 >/dev/null; done &
  echo 30bb0000.spi >/sys/bus/platform/drivers/fsl-quadspi/unbind

To fix this, explicitly call spi_unregister_controller() in the
remove() callback. This ensures that all child devices are properly
removed before the host is disabled.

Cc: stable@vger.kernel.org
Fixes: 8fcb830a00f0 ("spi: spi-fsl-qspi: use devm_spi_register_controller")
Signed-off-by: Kevin Hao <haokexin@gmail.com>
---
 drivers/spi/spi-fsl-qspi.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/drivers/spi/spi-fsl-qspi.c b/drivers/spi/spi-fsl-qspi.c
index efd87f44c63a5b12b76538aa459ca8eb203b9dcd..4767d2085510c2f231476ba75e46f83271c4c645 100644
--- a/drivers/spi/spi-fsl-qspi.c
+++ b/drivers/spi/spi-fsl-qspi.c
@@ -272,6 +272,7 @@ struct fsl_qspi {
 	struct device *dev;
 	int selected;
 	u32 memmap_phy;
+	struct spi_controller *host;
 };
 
 static inline int needs_swap_endian(struct fsl_qspi *q)
@@ -862,6 +863,7 @@ static int fsl_qspi_probe(struct platform_device *pdev)
 
 	q = spi_controller_get_devdata(ctlr);
 	q->dev = dev;
+	q->host = ctlr;
 	q->devtype_data = of_device_get_match_data(dev);
 	if (!q->devtype_data) {
 		ret = -ENODEV;
@@ -934,7 +936,7 @@ static int fsl_qspi_probe(struct platform_device *pdev)
 
 	ctlr->dev.of_node = np;
 
-	ret = devm_spi_register_controller(dev, ctlr);
+	ret = spi_register_controller(ctlr);
 	if (ret)
 		goto err_destroy_mutex;
 
@@ -957,6 +959,8 @@ static void fsl_qspi_remove(struct platform_device *pdev)
 {
 	struct fsl_qspi *q = platform_get_drvdata(pdev);
 
+	spi_unregister_controller(q->host);
+
 	/* disable the hardware */
 	qspi_writel(q, QUADSPI_MCR_MDIS_MASK, q->iobase + QUADSPI_MCR);
 	qspi_writel(q, 0x0, q->iobase + QUADSPI_RSER);

-- 
2.48.1