Re: I2C: Fix unhandled fault in i2c-omap controller

Jean Delvare
2008-03-14T17:52:18Z

On Thu, 13 Mar 2008 17:51:24 +0200, Tony Lindgren wrote:
> Hi Jean,
>
> Here's an omap I2C fix that would be nice to get into 2.6.25 if still
> possible.

Review:

> commit 8e4f19286e68d38d589451ad2a10545f2c40032d
> Author: Tony Lindgren <tony-4v6yS6AI5VpBDgjK7y7TUQ@public.gmane.org>
> Date: Mon Feb 18 20:16:00 2008 -0800
>
> 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-DWxLp4Yu+b8AvxtiuMwx3w@public.gmane.org>
> Signed-off-by: Tony Lindgren <tony-4v6yS6AI5VpBDgjK7y7TUQ@public.gmane.org>
>
> diff --git a/drivers/i2c/busses/i2c-omap.c b/drivers/i2c/busses/i2c-omap.c
> index da66397..862dd69 100644
> --- a/drivers/i2c/busses/i2c-omap.c
> +++ b/drivers/i2c/busses/i2c-omap.c
> @@ -128,6 +128,8 @@ struct omap_i2c_dev {
> size_t buf_len;
> struct i2c_adapter adapter;
> unsigned rev1:1;
> + unsigned idle:1;
> + u16 iestate; /* Saved interrupt register */
> };
>
> static inline void omap_i2c_write_reg(struct omap_i2c_dev *i2c_dev,
> @@ -174,18 +176,30 @@ 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);

Reading OMAP_I2C_IV_REG but not doing anything with the value? This
deserves at least a comment if this is done on purpose (but then I
don't think you need the iv variable at all.)

> + 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)
> @@ -360,7 +374,7 @@ 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;
> @@ -374,7 +388,7 @@ 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;
> }
>
> @@ -403,6 +417,9 @@ 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 */
> @@ -457,6 +474,9 @@ 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);
> @@ -575,7 +595,7 @@ 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;
> @@ -610,7 +630,7 @@ omap_i2c_probe(struct platform_device *pdev)
> goto err_free_irq;
> }
>
> - omap_i2c_disable_clocks(dev);
> + omap_i2c_idle(dev);
>
> return 0;
>
> @@ -618,7 +638,7 @@ 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);

The rest of the patch looks OK to me.

--
Jean Delvare

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