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Subject[PATCH 4.4 17/23] spi: bcm2835aux: ensure interrupts are enabled for shared handler
Date
[ Upstream commit bc519d9574618e47a0c788000fb78da95e18d953 ]

The BCM2835 AUX SPI has a shared interrupt line (with AUX UART).
Downstream fixes this with an AUX irqchip to demux the IRQ sources and a
DT change which breaks compatibility with older kernels. The AUX irqchip
was already rejected for upstream[1] and the DT change would break
working systems if the DTB is updated to a newer one. The latter issue
was brought to my attention by Alex Graf.

The root cause however is a bug in the shared handler. Shared handlers
must check that interrupts are actually enabled before servicing the
interrupt. Add a check that the TXEMPTY or IDLE interrupts are enabled.

[1] https://patchwork.kernel.org/patch/9781221/

Cc: Alexander Graf <agraf@suse.de>
Cc: Marc Zyngier <marc.zyngier@arm.com>
Cc: Mark Brown <broonie@kernel.org>
Cc: Eric Anholt <eric@anholt.net>
Cc: Stefan Wahren <stefan.wahren@i2se.com>
Cc: Florian Fainelli <f.fainelli@gmail.com>
Cc: Ray Jui <rjui@broadcom.com>
Cc: Scott Branden <sbranden@broadcom.com>
Cc: bcm-kernel-feedback-list@broadcom.com
Cc: linux-spi@vger.kernel.org
Cc: linux-rpi-kernel@lists.infradead.org
Cc: linux-arm-kernel@lists.infradead.org
Signed-off-by: Rob Herring <robh@kernel.org>
Reviewed-by: Eric Anholt <eric@anholt.net>
Signed-off-by: Mark Brown <broonie@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/spi/spi-bcm2835aux.c | 5 +++++
1 file changed, 5 insertions(+)

diff --git a/drivers/spi/spi-bcm2835aux.c b/drivers/spi/spi-bcm2835aux.c
index 7de6f8472a810..6f4c6aa801f14 100644
--- a/drivers/spi/spi-bcm2835aux.c
+++ b/drivers/spi/spi-bcm2835aux.c
@@ -187,6 +187,11 @@ static irqreturn_t bcm2835aux_spi_interrupt(int irq, void *dev_id)
struct bcm2835aux_spi *bs = spi_master_get_devdata(master);
irqreturn_t ret = IRQ_NONE;

+ /* IRQ may be shared, so return if our interrupts are disabled */
+ if (!(bcm2835aux_rd(bs, BCM2835_AUX_SPI_CNTL1) &
+ (BCM2835_AUX_SPI_CNTL1_TXEMPTY | BCM2835_AUX_SPI_CNTL1_IDLE)))
+ return ret;
+
/* check if we have data to read */
while (bs->rx_len &&
(!(bcm2835aux_rd(bs, BCM2835_AUX_SPI_STAT) &
--
2.20.1


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