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    Subject[PATCH 4.4 020/101] spi: bcm2835aux: Fix controller unregister order
    Date
    From: Lukas Wunner <lukas@wunner.de>

    commit b9dd3f6d417258ad0beeb292a1bc74200149f15d upstream.

    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>
    Link: https://lore.kernel.org/r/32f27f4d8242e4d75f9a53f7e8f1f77483b08669.1589557526.git.lukas@wunner.de
    Signed-off-by: Mark Brown <broonie@kernel.org>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    drivers/spi/spi-bcm2835aux.c | 4 +++-
    1 file changed, 3 insertions(+), 1 deletion(-)

    --- a/drivers/spi/spi-bcm2835aux.c
    +++ b/drivers/spi/spi-bcm2835aux.c
    @@ -457,7 +457,7 @@ static int bcm2835aux_spi_probe(struct p
    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;
    @@ -477,6 +477,8 @@ static int bcm2835aux_spi_remove(struct
    struct spi_master *master = platform_get_drvdata(pdev);
    struct bcm2835aux_spi *bs = spi_master_get_devdata(master);

    + spi_unregister_master(master);
    +
    bcm2835aux_spi_reset_hw(bs);

    /* disable the HW block by releasing the clock */

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