linux-kernel - Re: [PATCH 1/8] i2c: i2c-bfin-twi: Illegal i2c bus lock upon certain transfer scenarios.

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Message-ID: <CAJxxZ0MyEFfs9MT8ffZroUXtxsZ2ftd2Zky4ktywF4yeD9__nw@mail.gmail.com>
Date:	Thu, 24 May 2012 17:17:27 +0800
From:	Sonic Zhang <sonic.adi@...il.com>
To:	sonic.zhang@...log.com
Cc:	Ben Dooks <ben-linux@...ff.org>,
	Wolfram Sang <w.sang@...gutronix.de>,
	linux-i2c@...r.kernel.org, LKML <linux-kernel@...r.kernel.org>,
	uclinux-dist-devel@...ckfin.uclinux.org,
	Michael Hennerich <michael.hennerich@...log.com>
Subject: Re: [PATCH 1/8] i2c: i2c-bfin-twi: Illegal i2c bus lock upon certain
 transfer scenarios.

PING


On Wed, May 16, 2012 at 3:20 PM,  <sonic.zhang@...log.com> wrote:
> From: Michael Hennerich <michael.hennerich@...log.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@...log.com>
> Signed-off-by: Sonic Zhang <sonic.zhang@...log.com>
>
> git-svn-id: svn://localhost/svn/linux-kernel/trunk@...1 526b6c2d-f592-4532-a319-5dd88ccb003d
> ---
>  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);
>                        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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