[PATCH AUTOSEL 4.9 5/7] i2c: emev2: avoid race when unregistering slave client

[Sasha Levin]

From: Wolfram Sang <wsa+rene...@sang-engineering.com>

[ Upstream commit d7437fc0d8291181debe032671a289b6bd93f46f ]

After we disabled interrupts, there might still be an active one
running. Sync before clearing the pointer to the slave device.

Fixes: c31d0a00021d ("i2c: emev2: add slave support")
Reported-by: Krzysztof Adamski <krzysztof.adam...@nokia.com>
Signed-off-by: Wolfram Sang <wsa+rene...@sang-engineering.com>
Reviewed-by: Krzysztof Adamski <krzysztof.adam...@nokia.com>
Signed-off-by: Wolfram Sang <w...@the-dreams.de>
Signed-off-by: Sasha Levin <sas...@kernel.org>
---
 drivers/i2c/busses/i2c-emev2.c | 16 ++++++++++++----
 1 file changed, 12 insertions(+), 4 deletions(-)

diff --git a/drivers/i2c/busses/i2c-emev2.c b/drivers/i2c/busses/i2c-emev2.c
index 96bb4e7490128..0218ba6eb26ab 100644
--- a/drivers/i2c/busses/i2c-emev2.c
+++ b/drivers/i2c/busses/i2c-emev2.c
@@ -72,6 +72,7 @@ struct em_i2c_device {
        struct completion msg_done;
        struct clk *sclk;
        struct i2c_client *slave;
+       int irq;
 };
 
 static inline void em_clear_set_bit(struct em_i2c_device *priv, u8 clear, u8 
set, u8 reg)
@@ -342,6 +343,12 @@ static int em_i2c_unreg_slave(struct i2c_client *slave)
 
        writeb(0, priv->base + I2C_OFS_SVA0);
 
+       /*
+        * Wait for interrupt to finish. New slave irqs cannot happen because we
+        * cleared the slave address and, thus, only extension codes will be
+        * detected which do not use the slave ptr.
+        */
+       synchronize_irq(priv->irq);
        priv->slave = NULL;
 
        return 0;
@@ -358,7 +365,7 @@ static int em_i2c_probe(struct platform_device *pdev)
 {
        struct em_i2c_device *priv;
        struct resource *r;
-       int irq, ret;
+       int ret;
 
        priv = devm_kzalloc(&pdev->dev, sizeof(*priv), GFP_KERNEL);
        if (!priv)
@@ -391,8 +398,8 @@ static int em_i2c_probe(struct platform_device *pdev)
 
        em_i2c_reset(&priv->adap);
 
-       irq = platform_get_irq(pdev, 0);
-       ret = devm_request_irq(&pdev->dev, irq, em_i2c_irq_handler, 0,
+       priv->irq = platform_get_irq(pdev, 0);
+       ret = devm_request_irq(&pdev->dev, priv->irq, em_i2c_irq_handler, 0,
                                "em_i2c", priv);
        if (ret)
                goto err_clk;
@@ -402,7 +409,8 @@ static int em_i2c_probe(struct platform_device *pdev)
        if (ret)
                goto err_clk;
 
-       dev_info(&pdev->dev, "Added i2c controller %d, irq %d\n", 
priv->adap.nr, irq);
+       dev_info(&pdev->dev, "Added i2c controller %d, irq %d\n", priv->adap.nr,
+                priv->irq);
 
        return 0;
 
-- 
2.20.1