On Wed, Jun 13, 2012 at 04:22:44PM +0800, Sonic Zhang wrote:
> From: Sonic Zhang <sonic.zhang@xxxxxxxxxx>
>
> Current driver was developed based on BF537 0.2 HRM. In high system load, BUFRDERR error
> interrupt may be raised if XMTSERV interrupt of last TX byte is not served in time
> (set RSTART bit), which breaks restart tranfer as expected.
>
> "Buffer Read Error (BUFRDERR)" description in Blackfin HRM only applys to BF537
> rev. < 0.3. In later rev. and later announced Blackfin chips, such as BF527 and
> BF548, a new TWI master feature "Clock Stretching" is added into the TWI controller,
> BUFRDERR interrupt is not triggered after TX FIFO is empty.
>
> This patch sets RSTART bit at the beginning of the first transfer. The SCL and SDA
> is hold till XMTSERV interrupt of last TX byte is served. Restart transfer is not broken
> in high system load.
>
> Signed-off-by: Sonic Zhang <sonic.zhang@xxxxxxxxxx>
> ---
> drivers/i2c/busses/i2c-bfin-twi.c | 23 +++++++++++++----------
> 1 files changed, 13 insertions(+), 10 deletions(-)
>
> diff --git a/drivers/i2c/busses/i2c-bfin-twi.c b/drivers/i2c/busses/i2c-bfin-twi.c
> index 2e59bbd..e75ee91 100644
> --- a/drivers/i2c/busses/i2c-bfin-twi.c
> +++ b/drivers/i2c/busses/i2c-bfin-twi.c
> @@ -99,7 +99,7 @@ static void bfin_twi_handle_interrupt(struct bfin_twi_iface *iface,
> */
> else if (iface->cur_mode == TWI_I2C_MODE_COMBINED)
> write_MASTER_CTL(iface,
> - read_MASTER_CTL(iface) | MDIR | RSTART);
> + read_MASTER_CTL(iface) | MDIR);
> else if (iface->manual_stop)
> write_MASTER_CTL(iface,
> read_MASTER_CTL(iface) | STOP);
> @@ -107,10 +107,10 @@ static void bfin_twi_handle_interrupt(struct bfin_twi_iface *iface,
> iface->cur_msg + 1 < iface->msg_num) {
> if (iface->pmsg[iface->cur_msg + 1].flags & I2C_M_RD)
> write_MASTER_CTL(iface,
> - read_MASTER_CTL(iface) | RSTART | MDIR);
> + read_MASTER_CTL(iface) | MDIR);
> else
> write_MASTER_CTL(iface,
> - (read_MASTER_CTL(iface) | RSTART) & ~MDIR);
> + read_MASTER_CTL(iface) & ~MDIR);
> }
> }
> if (twi_int_status & RCVSERV) {
> @@ -144,10 +144,10 @@ static void bfin_twi_handle_interrupt(struct bfin_twi_iface *iface,
> iface->cur_msg + 1 < iface->msg_num) {
> if (iface->pmsg[iface->cur_msg + 1].flags & I2C_M_RD)
> write_MASTER_CTL(iface,
> - read_MASTER_CTL(iface) | RSTART | MDIR);
> + read_MASTER_CTL(iface) | MDIR);
> else
> write_MASTER_CTL(iface,
> - (read_MASTER_CTL(iface) | RSTART) & ~MDIR);
> + read_MASTER_CTL(iface) & ~MDIR);
> }
> }
> }
> @@ -262,9 +262,10 @@ static void bfin_twi_handle_interrupt(struct bfin_twi_iface *iface,
> (0xff << 6)));
> iface->manual_stop = 1;
> }
> - /* remove restart bit and enable master receive */
> - write_MASTER_CTL(iface,
> - read_MASTER_CTL(iface) & ~RSTART);
> + /* remove restart bit before last message */
> + if (iface->cur_msg+1 == iface->msg_num)
Spaces around operators. I fixed it for you.
> + write_MASTER_CTL(iface,
> + read_MASTER_CTL(iface) & ~RSTART);
> } else {
> iface->result = 1;
> write_INT_MASK(iface, 0);
> @@ -321,7 +322,8 @@ static int bfin_twi_do_master_xfer(struct i2c_adapter *adap,
> return -EINVAL;
> }
>
> - iface->cur_mode = TWI_I2C_MODE_REPEAT;
> + if (iface->msg_num > 1)
> + iface->cur_mode = TWI_I2C_MODE_REPEAT;
> iface->manual_stop = 0;
> iface->transPtr = pmsg->buf;
> iface->writeNum = iface->readNum = pmsg->len;
> @@ -366,6 +368,7 @@ static int bfin_twi_do_master_xfer(struct i2c_adapter *adap,
>
> /* Master enable */
> write_MASTER_CTL(iface, read_MASTER_CTL(iface) | MEN |
> + (iface->msg_num > 1 ? RSTART : 0) |
> ((iface->read_write == I2C_SMBUS_READ) ? MDIR : 0) |
> ((CONFIG_I2C_BLACKFIN_TWI_CLK_KHZ > 100) ? FAST : 0));
> SSYNC();
> @@ -530,7 +533,7 @@ int bfin_twi_do_smbus_xfer(struct i2c_adapter *adap, u16 addr,
> else
> write_MASTER_CTL(iface, 0x1 << 6);
> /* Master enable */
> - write_MASTER_CTL(iface, read_MASTER_CTL(iface) | MEN |
> + write_MASTER_CTL(iface, read_MASTER_CTL(iface) | MEN | RSTART |
> ((CONFIG_I2C_BLACKFIN_TWI_CLK_KHZ>100) ? FAST : 0));
> break;
> default:
> --
> 1.7.0.4
>
>
--
Pengutronix e.K. | Wolfram Sang |
Industrial Linux Solutions | http://www.pengutronix.de/ |
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