[PATCH AUTOSEL 4.19 23/27] i2c: emev2: avoid race when unregistering slave client

Sasha Levin
2019-08-20T13:42:52Z

From: Wolfram Sang <wsa+renesas@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.adamski@nokia.com>
Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Reviewed-by: Krzysztof Adamski <krzysztof.adamski@nokia.com>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>
Signed-off-by: Sasha Levin <sashal@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 35b302d983e0d..959d4912ec0d5 100644
--- a/drivers/i2c/busses/i2c-emev2.c
+++ b/drivers/i2c/busses/i2c-emev2.c
@@ -69,6 +69,7 @@ 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)
@@ -339,6 +340,12 @@ 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;
@@ -355,7 +362,7 @@ 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)
@@ -390,8 +397,8 @@ 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;
@@ -401,7 +408,8 @@ 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