Re: [PATCH] i2c: tegra: Check for overflow errors with BUG_ON.

Felipe Balbi
2011-08-15T19:17:55Z

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Hi,

On Mon, Aug 15, 2011 at 11:49:32AM -0700, Doug Anderson wrote:
> This change doesn't fix any known problems but turns
> on the overflow detection feature of the i2c controller
> in the hopes of flushing out any current (or future)
> bugs in the i2c driver.
>
> Inspired by a change on nvidia's git server:
> http://nv-tegra.nvidia.com/gitweb/?p=linux-2.6.git;a=commit;h=266d1b7397284505e55d06254b497cb32be07b69
>
> Signed-off-by: Doug Anderson <dianders@chromium.org>
> ---
> drivers/i2c/busses/i2c-tegra.c | 11 ++++++++---
> 1 files changed, 8 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/i2c/busses/i2c-tegra.c b/drivers/i2c/busses/i2c-tegra.c
> index 2440b74..4dbba23 100644
> --- a/drivers/i2c/busses/i2c-tegra.c
> +++ b/drivers/i2c/busses/i2c-tegra.c
> @@ -367,7 +367,8 @@ static int tegra_i2c_init(struct tegra_i2c_dev *i2c_dev)
> static irqreturn_t tegra_i2c_isr(int irq, void *dev_id)
> {
> u32 status;
> - const u32 status_err = I2C_INT_NO_ACK | I2C_INT_ARBITRATION_LOST;
> + const u32 status_err = I2C_INT_NO_ACK | I2C_INT_ARBITRATION_LOST |
> + I2C_INT_TX_FIFO_OVERFLOW;
> struct tegra_i2c_dev *i2c_dev = dev_id;
>
> status = i2c_readl(i2c_dev, I2C_INT_STATUS);
> @@ -389,6 +390,9 @@ static irqreturn_t tegra_i2c_isr(int irq, void *dev_id)
> }
>
> if (unlikely(status & status_err)) {
> + /* Don't pass this back--it can only happen due to a bug. */
> + BUG_ON(status & I2C_INT_TX_FIFO_OVERFLOW);

so due to a FIFO overflow you lock up the whole system ? Can't you e.g.
reset the controller and reconfigure it rather than locking up the
system ?

--
balbi

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