On Thu, Jan 17, 2013 at 12:42:47PM +0200, Mika Westerberg wrote: > On Thu, Jan 17, 2013 at 12:32:48PM +0200, Felipe Balbi wrote: > > 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 <[email protected]> > > > --- > > > 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. > > True but only if the driver exposes I2C_FUNC_PROTOCOL_MANGLING, which is > not done in this driver.
right, didn't check the driver, my bad. -- balbi
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