Hi,
On Thu, Jan 17, 2013 at 12:31:05PM +0200, Mika Westerberg wrote:
> If IC_EMPTYFIFO_HOLD_MASTER_EN is set to one, the DesignWare I2C controller
> doesn't generate STOP on the bus when the FIFO is empty. This violates the
> rules of Linux I2C stack as it requires that the STOP is issued once the
> i2c_transfer() is finished.
>
> However, there is no way to detect this from the hardware registers, so we
> must make sure that the STOP bit is always set once the last byte of the
> last message is transferred.
>
> This patch is based on the work of Dirk Brandewie.
>
> Signed-off-by: Mika Westerberg <mika.westerberg@xxxxxxxxxxxxxxx>
> ---
> drivers/i2c/busses/i2c-designware-core.c | 16 ++++++++++++++--
> 1 file changed, 14 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/i2c/busses/i2c-designware-core.c b/drivers/i2c/busses/i2c-designware-core.c
> index f5258c2..94fd818 100644
> --- a/drivers/i2c/busses/i2c-designware-core.c
> +++ b/drivers/i2c/busses/i2c-designware-core.c
> @@ -413,11 +413,23 @@ i2c_dw_xfer_msg(struct dw_i2c_dev *dev)
> rx_limit = dev->rx_fifo_depth - dw_readl(dev, DW_IC_RXFLR);
>
> while (buf_len > 0 && tx_limit > 0 && rx_limit > 0) {
> + u32 cmd = 0;
> +
> + /*
> + * If IC_EMPTYFIFO_HOLD_MASTER_EN is set we must
> + * manually set the stop bit. However, it cannot be
> + * detected from the registers so we set it always
> + * when writing/reading the last byte.
> + */
> + if (dev->msg_write_idx == dev->msgs_num - 1 &&
> + buf_len == 1)
> + cmd |= BIT(9);
> +
> if (msgs[dev->msg_write_idx].flags & I2C_M_RD) {
> - dw_writel(dev, 0x100, DW_IC_DATA_CMD);
> + dw_writel(dev, cmd | 0x100, DW_IC_DATA_CMD);
> rx_limit--;
> } else
> - dw_writel(dev, *buf++, DW_IC_DATA_CMD);
> + dw_writel(dev, cmd | *buf++, DW_IC_DATA_CMD);
also need to send STP bit if I2C_M_STOP is set.
--
balbi
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