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    SubjectRe: [PATCH 1/8] i2c: i2c-bfin-twi: Illegal i2c bus lock upon certain transfer scenarios.
    On Wed, May 16, 2012 at 03:20:19PM +0800, sonic.zhang@analog.com wrote:
    > From: Michael Hennerich <michael.hennerich@analog.com>
    >
    > For transfer counts > 255 bytes i2c-bfin-twi sets the data
    > transfer counter DCNT to 0xFF indicating unlimited transfers.
    > It then uses a flag iface->manual_stop to manually issue the STOP
    > condition, once the required amount of bytes are received.
    >
    > We found that on I2C receive operation issuing the STOP condition
    > together with a FULL RCV FIFO (2bytes) will cause SDA and SCL be
    > constantly driven low.
    >
    > Temporary workaround until further investigation:
    > Discard the RCV FIFO before issuing the STOP condition.
    >
    > Signed-off-by: Michael Hennerich <michael.hennerich@analog.com>
    > Signed-off-by: Sonic Zhang <sonic.zhang@analog.com>
    >
    > git-svn-id: svn://localhost/svn/linux-kernel/trunk@9011 526b6c2d-f592-4532-a319-5dd88ccb003d

    Please remove this line.

    > ---
    > drivers/i2c/busses/i2c-bfin-twi.c | 4 ++++
    > 1 files changed, 4 insertions(+), 0 deletions(-)
    >
    > diff --git a/drivers/i2c/busses/i2c-bfin-twi.c b/drivers/i2c/busses/i2c-bfin-twi.c
    > index cdb59e5..e6dd3c9 100644
    > --- a/drivers/i2c/busses/i2c-bfin-twi.c
    > +++ b/drivers/i2c/busses/i2c-bfin-twi.c
    > @@ -131,6 +131,10 @@ static void bfin_twi_handle_interrupt(struct bfin_twi_iface *iface,
    > iface->transPtr++;
    > iface->readNum--;
    > } else if (iface->manual_stop) {
    > + /* Avoid possible bus stall -
    > + * Flush FIFO before issuing the STOP condition
    > + */
    > + read_RCV_DATA16(iface);

    Please mention that this is currently only a workaround, so people know
    there could be still a proper solution.

    > write_MASTER_CTL(iface,
    > read_MASTER_CTL(iface) | STOP);
    > } else if (iface->cur_mode == TWI_I2C_MODE_REPEAT &&
    > --
    > 1.7.0.4
    >
    >

    --
    Pengutronix e.K. | Wolfram Sang |
    Industrial Linux Solutions | http://www.pengutronix.de/ |
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