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    Subject[PATCH 3.12 131/146] i2c: designware: Mask all interrupts during i2c controller enable
    Date
    From: "Du, Wenkai" <wenkai.du@intel.com>

    3.12-stable review patch. If anyone has any objections, please let me know.

    ===============

    commit 47bb27e78867997040a228328f2a631c3c7f2c82 upstream.

    There have been "i2c_designware 80860F41:00: controller timed out" errors
    on a number of Baytrail platforms. The issue is caused by incorrect value in
    Interrupt Mask Register (DW_IC_INTR_MASK) when i2c core is being enabled.
    This causes call to __i2c_dw_enable() to immediately start the transfer which
    leads to timeout. There are 3 failure modes observed:

    1. Failure in S0 to S3 resume path

    The default value after reset for DW_IC_INTR_MASK is 0x8ff. When we start
    the first transaction after resuming from system sleep, TX_EMPTY interrupt
    is already unmasked because of the hardware default.

    2. Failure in normal operational path

    This failure happens rarely and is hard to reproduce. Debug trace showed that
    DW_IC_INTR_MASK had value of 0x254 when failure occurred, which meant
    TX_EMPTY was unmasked.

    3. Failure in S3 to S0 suspend path

    This failure also happens rarely and is hard to reproduce. Adding debug trace
    that read DW_IC_INTR_MASK made this failure not reproducible. But from ISR
    call trace we could conclude TX_EMPTY was unmasked when problem occurred.

    The patch masks all interrupts before the controller is enabled to resolve the
    faulty DW_IC_INTR_MASK conditions.

    Signed-off-by: Wenkai Du <wenkai.du@intel.com>
    Acked-by: Mika Westerberg <mika.westerberg@linux.intel.com>
    [wsa: improved the comment and removed typo in commit msg]
    Signed-off-by: Wolfram Sang <wsa@the-dreams.de>
    Signed-off-by: Jiri Slaby <jslaby@suse.cz>
    ---
    drivers/i2c/busses/i2c-designware-core.c | 3 +++
    1 file changed, 3 insertions(+)

    diff --git a/drivers/i2c/busses/i2c-designware-core.c b/drivers/i2c/busses/i2c-designware-core.c
    index 5888feef1ac5..a4dd9bdf737b 100644
    --- a/drivers/i2c/busses/i2c-designware-core.c
    +++ b/drivers/i2c/busses/i2c-designware-core.c
    @@ -418,6 +418,9 @@ static void i2c_dw_xfer_init(struct dw_i2c_dev *dev)
    */
    dw_writel(dev, msgs[dev->msg_write_idx].addr | ic_tar, DW_IC_TAR);

    + /* enforce disabled interrupts (due to HW issues) */
    + i2c_dw_disable_int(dev);
    +
    /* Enable the adapter */
    __i2c_dw_enable(dev, true);

    --
    1.9.3


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