i2c: uniphier-f: make driver robust against concurrency

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>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>

diff --git a/drivers/i2c/busses/i2c-uniphier-f.c b/drivers/i2c/busses/i2c-uniphier-f.c
index a403e8579b652b6e2486f746b91b9357c3ab7381..200dfd1771af96ec6f975d3f83c3d3a11980dc6e 100644 (file)
--- 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 @@ complete:
 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;