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Subject[PATCH 1/3] i2c: uniphier-f: make driver robust against concurrency
Date
This is unlikely to happen, but it is possible for a CPU to enter
the interrupt handler just after wait_for_completion_timeout() has
expired. If this happens, the hardware is accessed from multiple
contexts concurrently.

Disable the IRQ after wait_for_completion_timeout(), and do nothing
from the handler when the IRQ is disabled.

Fixes: 6a62974b667f ("i2c: uniphier_f: add UniPhier FIFO-builtin I2C driver")
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
---

drivers/i2c/busses/i2c-uniphier-f.c | 17 ++++++++++++++++-
1 file changed, 16 insertions(+), 1 deletion(-)

diff --git a/drivers/i2c/busses/i2c-uniphier-f.c b/drivers/i2c/busses/i2c-uniphier-f.c
index a403e85..200dfd1 100644
--- a/drivers/i2c/busses/i2c-uniphier-f.c
+++ b/drivers/i2c/busses/i2c-uniphier-f.c
@@ -98,6 +98,7 @@ struct uniphier_fi2c_priv {
unsigned int flags;
unsigned int busy_cnt;
unsigned int clk_cycle;
+ spinlock_t lock; /* IRQ synchronization */
};

static void uniphier_fi2c_fill_txfifo(struct uniphier_fi2c_priv *priv,
@@ -162,7 +163,10 @@ static irqreturn_t uniphier_fi2c_interrupt(int irq, void *dev_id)
struct uniphier_fi2c_priv *priv = dev_id;
u32 irq_status;

+ spin_lock(&priv->lock);
+
irq_status = readl(priv->membase + UNIPHIER_FI2C_INT);
+ irq_status &= priv->enabled_irqs;

dev_dbg(&priv->adap.dev,
"interrupt: enabled_irqs=%04x, irq_status=%04x\n",
@@ -230,6 +234,8 @@ static irqreturn_t uniphier_fi2c_interrupt(int irq, void *dev_id)
goto handled;
}

+ spin_unlock(&priv->lock);
+
return IRQ_NONE;

data_done:
@@ -246,6 +252,8 @@ static irqreturn_t uniphier_fi2c_interrupt(int irq, void *dev_id)
handled:
uniphier_fi2c_clear_irqs(priv);

+ spin_unlock(&priv->lock);
+
return IRQ_HANDLED;
}

@@ -311,7 +319,7 @@ static int uniphier_fi2c_master_xfer_one(struct i2c_adapter *adap,
{
struct uniphier_fi2c_priv *priv = i2c_get_adapdata(adap);
bool is_read = msg->flags & I2C_M_RD;
- unsigned long time_left;
+ unsigned long time_left, flags;

dev_dbg(&adap->dev, "%s: addr=0x%02x, len=%d, stop=%d\n",
is_read ? "receive" : "transmit", msg->addr, msg->len, stop);
@@ -342,6 +350,12 @@ static int uniphier_fi2c_master_xfer_one(struct i2c_adapter *adap,
priv->membase + UNIPHIER_FI2C_CR);

time_left = wait_for_completion_timeout(&priv->comp, adap->timeout);
+
+ spin_lock_irqsave(&priv->lock, flags);
+ priv->enabled_irqs = 0;
+ uniphier_fi2c_set_irqs(priv);
+ spin_unlock_irqrestore(&priv->lock, flags);
+
if (!time_left) {
dev_err(&adap->dev, "transaction timeout.\n");
uniphier_fi2c_recover(priv);
@@ -529,6 +543,7 @@ static int uniphier_fi2c_probe(struct platform_device *pdev)

priv->clk_cycle = clk_rate / bus_speed;
init_completion(&priv->comp);
+ spin_lock_init(&priv->lock);
priv->adap.owner = THIS_MODULE;
priv->adap.algo = &uniphier_fi2c_algo;
priv->adap.dev.parent = dev;
--
2.7.4
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