Linux-SPI Archive on lore.kernel.org
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From: Lukas Wunner <lukas@wunner.de>
To: Mark Brown <broonie@kernel.org>
Cc: "Nicolas Saenz Julienne" <nsaenzjulienne@suse.de>,
	Martin Sperl <kernel@martin.sperl.org>,
	linux-spi@vger.kernel.org, linux-rpi-kernel@lists.infradead.org
Subject: [PATCH 3/5] spi: bcm2835aux: Fix controller unregister order
Date: Fri, 15 May 2020 17:58:03 +0200
Message-ID: <32f27f4d8242e4d75f9a53f7e8f1f77483b08669.1589557526.git.lukas@wunner.de> (raw)
In-Reply-To: <cover.1589557526.git.lukas@wunner.de>

The BCM2835aux SPI driver uses devm_spi_register_master() on bind.
As a consequence, on unbind, __device_release_driver() first invokes
bcm2835aux_spi_remove() before unregistering the SPI controller via
devres_release_all().

This order is incorrect:  bcm2835aux_spi_remove() turns off the SPI
controller, including its interrupts and clock.  The SPI controller
is thus no longer usable.

When the SPI controller is subsequently unregistered, it unbinds all
its slave devices.  If their drivers need to access the SPI bus,
e.g. to quiesce their interrupts, unbinding will fail.

As a rule, devm_spi_register_master() must not be used if the
->remove() hook performs teardown steps which shall be performed
after unbinding of slaves.

Fix by using the non-devm variant spi_register_master().  Note that the
struct spi_master as well as the driver-private data are not freed until
after bcm2835aux_spi_remove() has finished, so accessing them is safe.

Fixes: 1ea29b39f4c8 ("spi: bcm2835aux: add bcm2835 auxiliary spi device driver")
Signed-off-by: Lukas Wunner <lukas@wunner.de>
Cc: stable@vger.kernel.org # v4.4+
Cc: Martin Sperl <kernel@martin.sperl.org>
---
 drivers/spi/spi-bcm2835aux.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/spi/spi-bcm2835aux.c b/drivers/spi/spi-bcm2835aux.c
index a2162ff56a12..c331efd6e86b 100644
--- a/drivers/spi/spi-bcm2835aux.c
+++ b/drivers/spi/spi-bcm2835aux.c
@@ -569,7 +569,7 @@ static int bcm2835aux_spi_probe(struct platform_device *pdev)
 		goto out_clk_disable;
 	}
 
-	err = devm_spi_register_master(&pdev->dev, master);
+	err = spi_register_master(master);
 	if (err) {
 		dev_err(&pdev->dev, "could not register SPI master: %d\n", err);
 		goto out_clk_disable;
@@ -593,6 +593,8 @@ static int bcm2835aux_spi_remove(struct platform_device *pdev)
 
 	bcm2835aux_debugfs_remove(bs);
 
+	spi_unregister_master(master);
+
 	bcm2835aux_spi_reset_hw(bs);
 
 	/* disable the HW block by releasing the clock */
-- 
2.26.2


  parent reply index

Thread overview: 18+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-05-15 15:58 [PATCH 0/5] Raspberry Pi SPI unbind fixes Lukas Wunner
2020-05-15 15:58 ` [PATCH 1/5] spi: Fix controller unregister order Lukas Wunner
2020-05-15 16:27   ` Mark Brown
2020-05-15 16:31     ` Lukas Wunner
2020-05-15 21:37       ` Andy Shevchenko
2020-05-16  6:45         ` Lukas Wunner
2020-05-16  9:45           ` Andy Shevchenko
2020-05-15 15:58 ` [PATCH 2/5] spi: bcm2835: " Lukas Wunner
2020-05-15 16:29   ` Mark Brown
2020-05-15 16:44     ` Lukas Wunner
2020-05-15 21:33       ` Andy Shevchenko
2020-05-16  6:56         ` Lukas Wunner
2020-05-16  9:40           ` Andy Shevchenko
2020-05-15 15:58 ` Lukas Wunner [this message]
2020-05-15 15:58 ` [PATCH 4/5] spi: bcm2835: Tear down DMA before turning off SPI controller Lukas Wunner
2020-05-15 15:58 ` [PATCH 5/5] spi: Document devm_spi_register_controller() gotcha Lukas Wunner
2020-05-15 16:30   ` Mark Brown
2020-05-20 17:17 ` [PATCH 0/5] Raspberry Pi SPI unbind fixes Mark Brown

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