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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
>
>

--
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Industrial Linux Solutions | http://www.pengutronix.de/ |[unhandled content-type:application/pgp-signature]
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