Commit c15f6ed3 authored by Nicolas Boichat's avatar Nicolas Boichat Committed by Mark Brown
Browse files

spi: bitbang: Replace spinlock by mutex 



chipselect (in the case of spi-gpio: spi_gpio_chipselect, which
calls gpiod_set_raw_value_cansleep) can sleep, so we should not
hold a spinlock while calling it from spi_bitbang_setup.

This issue was introduced by this commit, which converted spi-gpio
to cansleep variants:
d9dda5a1 "spi: spi-gpio: Use 'cansleep' variants to access GPIO"

Replacing the lock variable by a mutex fixes the issue: This is
safe as all instances where the lock is used are called from
contexts that can sleep.

Finally, update spi-ppc4xx and and spi-s3c24xx to use mutex
functions, as they directly hold the lock for similar purpose.

Signed-off-by: default avatarNicolas Boichat <drinkcat@chromium.org>
Signed-off-by: default avatarMark Brown <broonie@kernel.org>
parent 6ff33f39

drivers/spi/spi-bitbang.c

+7 −10
Original line number Diff line number Diff line
@@ -180,7 +180,6 @@ int spi_bitbang_setup(struct spi_device *spi) 
{

	struct spi_bitbang_cs	*cs = spi->controller_state;

	struct spi_bitbang	*bitbang;

	unsigned long		flags;



	bitbang = spi_master_get_devdata(spi->master);
@@ -210,12 +209,12 @@ int spi_bitbang_setup(struct spi_device *spi) 
	 */



	/* deselect chip (low or high) */

	spin_lock_irqsave(&bitbang->lock, flags);

	mutex_lock(&bitbang->lock);

	if (!bitbang->busy) {

		bitbang->chipselect(spi, BITBANG_CS_INACTIVE);

		ndelay(cs->nsecs);

	}

	spin_unlock_irqrestore(&bitbang->lock, flags);

	mutex_unlock(&bitbang->lock);



	return 0;

}
@@ -255,13 +254,12 @@ static int spi_bitbang_bufs(struct spi_device *spi, struct spi_transfer *t) 
static int spi_bitbang_prepare_hardware(struct spi_master *spi)

{

	struct spi_bitbang	*bitbang;

	unsigned long		flags;



	bitbang = spi_master_get_devdata(spi);



	spin_lock_irqsave(&bitbang->lock, flags);

	mutex_lock(&bitbang->lock);

	bitbang->busy = 1;

	spin_unlock_irqrestore(&bitbang->lock, flags);

	mutex_unlock(&bitbang->lock);



	return 0;

}
@@ -378,13 +376,12 @@ static int spi_bitbang_transfer_one(struct spi_master *master, 
static int spi_bitbang_unprepare_hardware(struct spi_master *spi)

{

	struct spi_bitbang	*bitbang;

	unsigned long		flags;



	bitbang = spi_master_get_devdata(spi);



	spin_lock_irqsave(&bitbang->lock, flags);

	mutex_lock(&bitbang->lock);

	bitbang->busy = 0;

	spin_unlock_irqrestore(&bitbang->lock, flags);

	mutex_unlock(&bitbang->lock);



	return 0;

}
@@ -427,7 +424,7 @@ int spi_bitbang_start(struct spi_bitbang *bitbang) 
	if (!master || !bitbang->chipselect)

		return -EINVAL;



	spin_lock_init(&bitbang->lock);

	mutex_init(&bitbang->lock);



	if (!master->mode_bits)

		master->mode_bits = SPI_CPOL | SPI_CPHA | bitbang->flags;

drivers/spi/spi-ppc4xx.c

+2 −2
Original line number Diff line number Diff line
@@ -210,12 +210,12 @@ static int spi_ppc4xx_setupxfer(struct spi_device *spi, struct spi_transfer *t) 
	if (in_8(&hw->regs->cdm) != cdm)

		out_8(&hw->regs->cdm, cdm);



	spin_lock(&hw->bitbang.lock);

	mutex_lock(&hw->bitbang.lock);

	if (!hw->bitbang.busy) {

		hw->bitbang.chipselect(spi, BITBANG_CS_INACTIVE);

		/* Need to ndelay here? */

	}

	spin_unlock(&hw->bitbang.lock);

	mutex_unlock(&hw->bitbang.lock);



	return 0;

}

drivers/spi/spi-s3c24xx.c

+2 −2
Original line number Diff line number Diff line
@@ -198,12 +198,12 @@ static int s3c24xx_spi_setup(struct spi_device *spi) 
	if (ret)

		return ret;



	spin_lock(&hw->bitbang.lock);

	mutex_lock(&hw->bitbang.lock);

	if (!hw->bitbang.busy) {

		hw->bitbang.chipselect(spi, BITBANG_CS_INACTIVE);

		/* need to ndelay for 0.5 clocktick ? */

	}

	spin_unlock(&hw->bitbang.lock);

	mutex_unlock(&hw->bitbang.lock);



	return 0;

}

include/linux/spi/spi_bitbang.h

+1 −1
Original line number Diff line number Diff line
@@ -4,7 +4,7 @@ 
#include <linux/workqueue.h>



struct spi_bitbang {

	spinlock_t		lock;

	struct mutex		lock;

	u8			busy;

	u8			use_dma;

	u8			flags;		/* extra spi->mode support */

CRA Git | Maintained and supported by SUSTech CRA and CCSE