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    SubjectRe: [PATCH v2] i2c: tegra: Check for overflow errors with BUG_ON.
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    On Mon, 2011-08-15 at 18:32 -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>
    > ---
    > This takes Felipe Balbi's suggestion of making the overflow
    > error non-fatal.
    >
    > drivers/i2c/busses/i2c-tegra.c | 17 ++++++++++++++---
    > 1 files changed, 14 insertions(+), 3 deletions(-)
    >
    > diff --git a/drivers/i2c/busses/i2c-tegra.c b/drivers/i2c/busses/i2c-tegra.c
    > index 2440b74..34634b7 100644
    > --- a/drivers/i2c/busses/i2c-tegra.c
    > +++ b/drivers/i2c/busses/i2c-tegra.c
    > @@ -83,6 +83,7 @@
    > #define I2C_ERR_NO_ACK 0x01
    > #define I2C_ERR_ARBITRATION_LOST 0x02
    > #define I2C_ERR_UNKNOWN_INTERRUPT 0x04
    > +#define I2C_ERR_FIFO_OVERFLOW 0x08
    >
    > #define PACKET_HEADER0_HEADER_SIZE_SHIFT 28
    > #define PACKET_HEADER0_PACKET_ID_SHIFT 16
    > @@ -367,7 +368,8 @@ 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 +391,14 @@ static irqreturn_t tegra_i2c_isr(int irq, void *dev_id)
    > }
    >
    > if (unlikely(status & status_err)) {
    > + /*
    > + * Overflow should be impossible unless we've got a
    > + * bug in the driver, but check anyway.
    > + */
    > + if (status & I2C_INT_TX_FIFO_OVERFLOW) {
    > + WARN_ON(1);
    > + i2c_dev->msg_err |= I2C_ERR_FIFO_OVERFLOW;
    > + }
    > if (status & I2C_INT_NO_ACK)
    > i2c_dev->msg_err |= I2C_ERR_NO_ACK;
    > if (status & I2C_INT_ARBITRATION_LOST)
    > @@ -423,7 +433,7 @@ err:
    > /* An error occurred, mask all interrupts */
    > tegra_i2c_mask_irq(i2c_dev, I2C_INT_NO_ACK | I2C_INT_ARBITRATION_LOST |
    > I2C_INT_PACKET_XFER_COMPLETE | I2C_INT_TX_FIFO_DATA_REQ |
    > - I2C_INT_RX_FIFO_DATA_REQ);
    > + I2C_INT_RX_FIFO_DATA_REQ | I2C_INT_TX_FIFO_OVERFLOW);
    > i2c_writel(i2c_dev, status, I2C_INT_STATUS);
    > if (i2c_dev->is_dvc)
    > dvc_writel(i2c_dev, DVC_STATUS_I2C_DONE_INTR, DVC_STATUS);
    > @@ -473,7 +483,8 @@ static int tegra_i2c_xfer_msg(struct tegra_i2c_dev *i2c_dev,
    > if (!(msg->flags & I2C_M_RD))
    > tegra_i2c_fill_tx_fifo(i2c_dev);
    >
    > - int_mask = I2C_INT_NO_ACK | I2C_INT_ARBITRATION_LOST;
    > + int_mask = I2C_INT_NO_ACK | I2C_INT_ARBITRATION_LOST |
    > + I2C_INT_TX_FIFO_OVERFLOW;
    > if (msg->flags & I2C_M_RD)
    > int_mask |= I2C_INT_RX_FIFO_DATA_REQ;
    > else if (i2c_dev->msg_buf_remaining)

    Seems good to me.

    Acked-by: Rhyland Klein <rklein@nvidia.com>




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