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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:
d9dda5a191 "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: Nicolas Boichat <drinkcat@chromium.org>
Signed-off-by: Mark Brown <broonie@kernel.org>
hifive-unleashed-5.1
Nicolas Boichat 2015-08-17 11:52:54 +08:00 committed by Mark Brown
parent 6ff33f3902
commit c15f6ed3a1
4 changed files with 12 additions and 15 deletions
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17
drivers/spi/spi-bitbang.c
View File

@ -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;

4
drivers/spi/spi-ppc4xx.c
View File

@ -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;
}

4
drivers/spi/spi-s3c24xx.c
View File

@ -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;
}

2
include/linux/spi/spi_bitbang.h
View File

@ -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 */