Subject: [PATCH 4.9 18/26] spi: bcm2835aux: ensure interrupts are enabled for shared handler

From: Greg Kroah-Hartman <[email-masked]>
Date: Sun, 8 Sep 2019 13:41:57 +0100

[ 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 <[email-masked]>
Cc: Marc Zyngier <[email-masked]>
Cc: Mark Brown <[email-masked]>
Cc: Eric Anholt <[email-masked]>
Cc: Stefan Wahren <[email-masked]>
Cc: Florian Fainelli <[email-masked]>
Cc: Ray Jui <[email-masked]>
Cc: Scott Branden <[email-masked]>
Cc: [email-masked]
Cc: [email-masked]
Cc: [email-masked]
Cc: [email-masked]
Signed-off-by: Rob Herring <[email-masked]>
Reviewed-by: Eric Anholt <[email-masked]>
Signed-off-by: Mark Brown <[email-masked]>
Signed-off-by: Sasha Levin <[email-masked]>
---
 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 7428091d3f5b8..bd00b7cc8b78b 100644
--- a/drivers/spi/spi-bcm2835aux.c
+++ b/drivers/spi/spi-bcm2835aux.c
@@ -184,6 +184,11 @@ 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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