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>

4 files changed, 12 insertions, 15 deletions

diff --git a/drivers/spi/spi-bitbang.c b/drivers/spi/spi-bitbang.c
index 840a4984d365..ef43ef507c9a 100644
--- a/drivers/spi/spi-bitbang.c
+++ b/drivers/spi/spi-bitbang.c
@@ -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;
diff --git a/drivers/spi/spi-ppc4xx.c b/drivers/spi/spi-ppc4xx.c
index 54fb984a3e17..dd3d0a218d8b 100644
--- a/drivers/spi/spi-ppc4xx.c
+++ b/drivers/spi/spi-ppc4xx.c
@@ -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;
 }
diff --git a/drivers/spi/spi-s3c24xx.c b/drivers/spi/spi-s3c24xx.c
index f36bc320a807..4e7d1bfed7e6 100644
--- a/drivers/spi/spi-s3c24xx.c
+++ b/drivers/spi/spi-s3c24xx.c
@@ -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;
 }
diff --git a/include/linux/spi/spi_bitbang.h b/include/linux/spi/spi_bitbang.h
index 85578d4be034..154788ed218c 100644
--- a/include/linux/spi/spi_bitbang.h
+++ b/include/linux/spi/spi_bitbang.h
@@ -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 */