linux-kernel - [PATCH 4.16 178/279] spi: bcm2835aux: ensure interrupts are enabled for shared handler

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Date:   Mon, 18 Jun 2018 10:12:43 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Alexander Graf <agraf@...e.de>,
        Marc Zyngier <marc.zyngier@....com>,
        Mark Brown <broonie@...nel.org>, Eric Anholt <eric@...olt.net>,
        Stefan Wahren <stefan.wahren@...e.com>,
        Florian Fainelli <f.fainelli@...il.com>,
        Ray Jui <rjui@...adcom.com>,
        Scott Branden <sbranden@...adcom.com>,
        bcm-kernel-feedback-list@...adcom.com, linux-spi@...r.kernel.org,
        linux-rpi-kernel@...ts.infradead.org,
        linux-arm-kernel@...ts.infradead.org,
        Rob Herring <robh@...nel.org>,
        Sasha Levin <alexander.levin@...rosoft.com>
Subject: [PATCH 4.16 178/279] spi: bcm2835aux: ensure interrupts are enabled for shared handler

4.16-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Rob Herring <robh@...nel.org>

[ 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@...e.de>
Cc: Marc Zyngier <marc.zyngier@....com>
Cc: Mark Brown <broonie@...nel.org>
Cc: Eric Anholt <eric@...olt.net>
Cc: Stefan Wahren <stefan.wahren@...e.com>
Cc: Florian Fainelli <f.fainelli@...il.com>
Cc: Ray Jui <rjui@...adcom.com>
Cc: Scott Branden <sbranden@...adcom.com>
Cc: bcm-kernel-feedback-list@...adcom.com
Cc: linux-spi@...r.kernel.org
Cc: linux-rpi-kernel@...ts.infradead.org
Cc: linux-arm-kernel@...ts.infradead.org
Signed-off-by: Rob Herring <robh@...nel.org>
Reviewed-by: Eric Anholt <eric@...olt.net>
Signed-off-by: Mark Brown <broonie@...nel.org>
Signed-off-by: Sasha Levin <alexander.levin@...rosoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 drivers/spi/spi-bcm2835aux.c |    5 +++++
 1 file changed, 5 insertions(+)

--- a/drivers/spi/spi-bcm2835aux.c
+++ b/drivers/spi/spi-bcm2835aux.c
@@ -184,6 +184,11 @@ static irqreturn_t bcm2835aux_spi_interr
 	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) &