On Tue, Sep 12, 2023 at 07:45:36AM +0200, Gerald Loacker wrote:
>
>
> Am 08.09.2023 um 15:53 schrieb Sascha Hauer:
> > On Fri, Sep 08, 2023 at 12:16:46PM +0200, Gerald Loacker wrote:
> >> The i2c bus gets disabled without sending a stop condition. This violates
> >> i2c timing on the clock line. Fix this and include all related functions
> >> (rk_i2c_send_start_bit, rk_i2c_send_stop_bit, rk_i2c_disable) onto the same
> >> level.
> >>
> >> Signed-off-by: Gerald Loacker <gerald.loacker@xxxxxxxxxxxxxx>
> >> ---
> >> drivers/i2c/busses/i2c-rockchip.c | 21 ++++++++-------------
> >> 1 file changed, 8 insertions(+), 13 deletions(-)
> >>
> >> @@ -387,6 +376,11 @@ static int rockchip_i2c_xfer(struct i2c_adapter *adapter, struct i2c_msg *msgs,
> >> struct i2c_msg *msg = &msgs[i];
> >>
> >> dev_dbg(dev, "i2c_xfer: chip=0x%x, len=0x%x\n", msg->addr, msg->len);
> >> +
> >> + ret = rk_i2c_send_start_bit(i2c);
> >> + if (ret)
> >> + break;
> >> +
> >> if (msg->flags & I2C_M_RD) {
> >> ret = rk_i2c_read(i2c, msg->addr, 0, 0, msg->buf,
> >> msg->len);
> >> @@ -394,6 +388,9 @@ static int rockchip_i2c_xfer(struct i2c_adapter *adapter, struct i2c_msg *msgs,
> >> ret = rk_i2c_write(i2c, msg->addr, 0, 0, msg->buf,
> >> msg->len);
> >> }
> >> +
> >> + rk_i2c_send_stop_bit(i2c);
> >> +
> >> if (ret) {
> >> dev_dbg(dev, "i2c_write: error sending: %pe\n",
> >> ERR_PTR(ret));
> >> @@ -402,9 +399,7 @@ static int rockchip_i2c_xfer(struct i2c_adapter *adapter, struct i2c_msg *msgs,
> >> }
> >> }
> >>
> >> - rk_i2c_send_stop_bit(i2c);
> >
> > I believe this is wrong. A stop bit should only be sent after the last
> > message, not after all messages.
> >
>
> Your're right. This was just because the repeated start does not work
> consitently in our case. I'll come up with another approach.
Might be worth to look at the kernel driver. It has a comment about
this:
/*
* The HW is actually not capable of REPEATED START. But we can
* get the intended effect by resetting its internal state
* and issuing an ordinary START.
*/
ctrl = i2c_readl(i2c, REG_CON) & REG_CON_TUNING_MASK;
i2c_writel(i2c, ctrl, REG_CON);
Sascha
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