cw1200: Don't perform SPI transfers in interrupt context

When we get an interrupt from the hardware, the first thing the driver does
is tell the device to mask off the interrupt line.  Unfortunately this
involves a SPI transaction in interrupt context.  Some (most?) SPI
controllers perform the transfer asynchronously and try to sleep.
This is bad, and triggers a BUG().

So, work around this by using adding a hwbus hook for the cw1200 driver
core to call.  The cw1200_spi driver translates this into
irq_disable()/irq_enable() calls instead, which can safely be called in
interrupt context.

Apparently the platforms I used to develop the cw1200_spi driver used
synchronous spi_sync() implementations, which is why this didn't surface
until now.

Many thanks to Dave Sizeburns for the inital bug report and his services
as a tester.

Signed-off-by: Solomon Peachy <pizza@shaftnet.org>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

1 files changed, 16 insertions, 3 deletions

diff --git a/drivers/net/wireless/cw1200/cw1200_spi.c b/drivers/net/wireless/cw1200/cw1200_spi.c
index d06376014bcd..c31580ba883b 100644
--- a/drivers/net/wireless/cw1200/cw1200_spi.c
+++ b/drivers/net/wireless/cw1200/cw1200_spi.c
@@ -41,6 +41,7 @@ struct hwbus_priv {
 	const struct cw1200_platform_data_spi *pdata;
 	spinlock_t		lock; /* Serialize all bus operations */
 	int claimed;
+	int irq_disabled;
 };
 
 #define SDIO_TO_SPI_ADDR(addr) ((addr & 0x1f)>>2)
@@ -230,6 +231,8 @@ static irqreturn_t cw1200_spi_irq_handler(int irq, void *dev_id)
 	struct hwbus_priv *self = dev_id;
 
 	if (self->core) {
+		disable_irq_nosync(self->func->irq);
+		self->irq_disabled = 1;
 		cw1200_irq_handler(self->core);
 		return IRQ_HANDLED;
 	} else {
@@ -263,13 +266,22 @@ exit:
 
 static int cw1200_spi_irq_unsubscribe(struct hwbus_priv *self)
 {
-	int ret = 0;
-
 	pr_debug("SW IRQ unsubscribe\n");
 	disable_irq_wake(self->func->irq);
 	free_irq(self->func->irq, self);
 
-	return ret;
+	return 0;
+}
+
+static int cw1200_spi_irq_enable(struct hwbus_priv *self, int enable)
+{
+	/* Disables are handled by the interrupt handler */
+	if (enable && self->irq_disabled) {
+		enable_irq(self->func->irq);
+		self->irq_disabled = 0;
+	}
+
+	return 0;
 }
 
 static int cw1200_spi_off(const struct cw1200_platform_data_spi *pdata)
@@ -349,6 +361,7 @@ static struct hwbus_ops cw1200_spi_hwbus_ops = {
 	.unlock			= cw1200_spi_unlock,
 	.align_size		= cw1200_spi_align_size,
 	.power_mgmt		= cw1200_spi_pm,
+	.irq_enable             = cw1200_spi_irq_enable,
 };
 
 /* Probe Function to be called by SPI stack when device is discovered */