From: Antonio Borneo <antonio.borneo@xxxxxxxxxxx>
[ Upstream commit 8d559a64f00b59af9cc02b803ff52f6e6880a651 ]
A call to spi_unregister_master() triggers calling remove()
for all the spi devices binded to the spi master.
Some spi device driver requires to "talk" with the spi device
during the remove(), e.g.:
- a LCD panel like drivers/gpu/drm/panel/panel-lg-lg4573.c
will turn off the backlighting sending a command over spi.
This implies that the spi master must be fully functional when
spi_unregister_master() is called, either if it is called
explicitly in the master's remove() code or implicitly by the
devres framework.
Devres calls devres_release_all() to release all the resources
"after" the remove() of the spi master driver (check code of
__device_release_driver() in drivers/base/dd.c).
If the spi master driver has an empty remove() then there would
be no issue; the devres_release_all() will release everything
in reverse order w.r.t. probe().
But if code in spi master driver remove() disables the spi or
makes it not functional (like in this spi-stm32), then devres
cannot be used safely for unregistering the spi master and the
binded spi devices.
Replace devm_spi_register_master() with spi_register_master()
and add spi_unregister_master() as first action in remove().
Fixes: dcbe0d84dfa5 ("spi: add driver for STM32 SPI controller")
Signed-off-by: Antonio Borneo <antonio.borneo@xxxxxxxxxxx>
Signed-off-by: Alain Volmat <alain.volmat@xxxxxxxxxxx>
Link: https://lore.kernel.org/r/1615545286-5395-1-git-send-email-alain.volmat@xxxxxxxxxxx
Signed-off-by: Mark Brown <broonie@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
drivers/spi/spi-stm32.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/drivers/spi/spi-stm32.c b/drivers/spi/spi-stm32.c
index 53c4311cc6ab..8d8a32d46f2d 100644
--- a/drivers/spi/spi-stm32.c
+++ b/drivers/spi/spi-stm32.c
@@ -1950,7 +1950,7 @@ static int stm32_spi_probe(struct platform_device *pdev)
pm_runtime_set_active(&pdev->dev);
pm_runtime_enable(&pdev->dev);
- ret = devm_spi_register_master(&pdev->dev, master);
+ ret = spi_register_master(master);
if (ret) {
dev_err(&pdev->dev, "spi master registration failed: %d\n",
ret);
@@ -1987,6 +1987,7 @@ static int stm32_spi_remove(struct platform_device *pdev)
struct spi_master *master = platform_get_drvdata(pdev);
struct stm32_spi *spi = spi_master_get_devdata(master);
+ spi_unregister_master(master);
spi->cfg->disable(spi);
if (master->dma_tx)
--
2.30.2
