I2C: Fix unhandled fault in i2c-omap controller

If an I2C interrupt happens between disabling interface clock
and functional clock, the interrupt handler will produce an
external abort on non-linefetch error when trying to access
driver registers while interface clock is disabled.

This patch fixes the problem by saving and disabling i2c-omap
interrupt before turning off the clocks. Also disable functional
clock before the interface clock as suggested by Paul Walmsley.

Patch also renames enable/disable_clocks functions to unidle/idle
functions. Note that the driver is currently not taking advantage
of the idle interrupts. To use the idle interrupts, driver would
have to enable interface clock based on the idle interrupt
and dev->idle flag.

Cc: Paul Walmsley <paul@pwsan.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>

diff --git a/drivers/i2c/busses/i2c-omap.c b/drivers/i2c/busses/i2c-omap.c
index 9903e35d0b20966b3245f78869ff7b4873fd5111..4777466437e15397a771fbe56dd9e3bf38abc379 100644 (file)
--- a/drivers/i2c/busses/i2c-omap.c
+++ b/drivers/i2c/busses/i2c-omap.c
@@ -145,6 +145,8 @@ struct omap_i2c_dev {
                                                 */
        unsigned                rev1:1;
        unsigned                b_hw:1;         /* bad h/w fixes */
+       unsigned                idle:1;
+       u16                     iestate;        /* Saved interrupt register */
 };
 
 static inline void omap_i2c_write_reg(struct omap_i2c_dev *i2c_dev,
@@ -202,18 +204,30 @@ static void omap_i2c_put_clocks(struct omap_i2c_dev *dev)
        }
 }
 
-static void omap_i2c_enable_clocks(struct omap_i2c_dev *dev)
+static void omap_i2c_unidle(struct omap_i2c_dev *dev)
 {
        if (dev->iclk != NULL)
                clk_enable(dev->iclk);
        clk_enable(dev->fclk);
+       if (dev->iestate)
+               omap_i2c_write_reg(dev, OMAP_I2C_IE_REG, dev->iestate);
+       dev->idle = 0;
 }
 
-static void omap_i2c_disable_clocks(struct omap_i2c_dev *dev)
+static void omap_i2c_idle(struct omap_i2c_dev *dev)
 {
+       u16 iv;
+
+       dev->idle = 1;
+       dev->iestate = omap_i2c_read_reg(dev, OMAP_I2C_IE_REG);
+       omap_i2c_write_reg(dev, OMAP_I2C_IE_REG, 0);
+       if (dev->rev1)
+               iv = omap_i2c_read_reg(dev, OMAP_I2C_IV_REG);
+       else
+               omap_i2c_write_reg(dev, OMAP_I2C_STAT_REG, dev->iestate);
+       clk_disable(dev->fclk);
        if (dev->iclk != NULL)
                clk_disable(dev->iclk);
-       clk_disable(dev->fclk);
 }
 
 static int omap_i2c_init(struct omap_i2c_dev *dev)
@@ -474,7 +488,7 @@ omap_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg msgs[], int num)
        int i;
        int r;
 
-       omap_i2c_enable_clocks(dev);
+       omap_i2c_unidle(dev);
 
        if ((r = omap_i2c_wait_for_bb(dev)) < 0)
                goto out;
@@ -488,7 +502,7 @@ omap_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg msgs[], int num)
        if (r == 0)
                r = num;
 out:
-       omap_i2c_disable_clocks(dev);
+       omap_i2c_idle(dev);
        return r;
 }
 
@@ -521,6 +535,9 @@ omap_i2c_rev1_isr(int this_irq, void *dev_id)
        struct omap_i2c_dev *dev = dev_id;
        u16 iv, w;
 
+       if (dev->idle)
+               return IRQ_NONE;
+
        iv = omap_i2c_read_reg(dev, OMAP_I2C_IV_REG);
        switch (iv) {
        case 0x00:      /* None */
@@ -575,6 +592,9 @@ omap_i2c_isr(int this_irq, void *dev_id)
        u16 stat, w;
        int count = 0;
 
+       if (dev->idle)
+               return IRQ_NONE;
+
        bits = omap_i2c_read_reg(dev, OMAP_I2C_IE_REG);
        while ((stat = (omap_i2c_read_reg(dev, OMAP_I2C_STAT_REG))) & bits) {
                dev_dbg(dev->dev, "IRQ (ISR = 0x%04x)\n", stat);
@@ -731,7 +751,7 @@ omap_i2c_probe(struct platform_device *pdev)
        if ((r = omap_i2c_get_clocks(dev)) != 0)
                goto err_free_mem;
 
-       omap_i2c_enable_clocks(dev);
+       omap_i2c_unidle(dev);
 
        if (cpu_is_omap15xx())
                dev->rev1 = omap_i2c_read_reg(dev, OMAP_I2C_REV_REG) < 0x20;
@@ -779,7 +799,7 @@ omap_i2c_probe(struct platform_device *pdev)
                goto err_free_irq;
        }
 
-       omap_i2c_disable_clocks(dev);
+       omap_i2c_idle(dev);
 
        return 0;
 
@@ -787,7 +807,7 @@ err_free_irq:
        free_irq(dev->irq, dev);
 err_unuse_clocks:
        omap_i2c_write_reg(dev, OMAP_I2C_CON_REG, 0);
-       omap_i2c_disable_clocks(dev);
+       omap_i2c_idle(dev);
        omap_i2c_put_clocks(dev);
 err_free_mem:
        platform_set_drvdata(pdev, NULL);