[PATCH] i2c: rk3x: Disable the controller between transfers

[Alexey Charkov]

Hi Shawn,

On Fri, Oct 16, 2026 at 4:33 AM Shawn Lin <shawn.lin at rock-chips.com> wrote:
>
> Cc: + David
>
> 在 2026/10/15 星期四 22:00, Alexey Charkov 写道:
> > The driver leaves the controller enabled once a transfer completes, and
> > an enabled controller keeps tracking the bus. If the lines collapse under
> > it while idle, as happens when a target's supply is switched off while
> > its bus pull-ups stay powered, its state machine wedges driving SDA low.
> > Every later transfer then times out, since the timeout path only requests
> > a STOP and never disables the controller, and the stuck state even
> > survives a kexec.
> >
> > Clear the enable bit once each transfer is done, successful or not, so
> > that the controller does not watch an idle bus and starts every transfer
> > from a clean state.
> >
>
> I checked the vendor kernel tree and saw another case that you perhaps
> need to fold something similar below into your patch, along with your
> disabling controller?
>
>      In some case，log like this:
>
>      [   12.393926] rk3x-i2c ff150000.i2c: irq in STATE_IDLE, ipd = 0x51
>      [   12.416592] rk3x-i2c ff150000.i2c: irq in STATE_IDLE, ipd = 0x51
>
>      The i2c clock is disabled, so the pending irq clean is not
>      worked. Disable the interrupt after the i2c jobs were done,
>      the error log would not happen.
>
>
> /* Disable i2c all irqs */
> #define IEN_ALL_DISABLE   0
>
> i2c_writel(i2c, IEN_ALL_DISABLE, REG_IEN);i2c_writel(i2c,
> IEN_ALL_DISABLE, REG_IEN);

Thanks for looking into this! Do you happen to have a reproducer or
any additional info on how this state gets triggered? I haven't run
into it in my setups - did I just get lucky? :)

I see the same write of 0 to REG_IEN just above my changed lines for
the case if (time_left == 0), which makes sense because a
too-long-running transfer might eventually complete and trigger the
interrupt with the controller disabled, unless the interrupt is
disabled too. For other cases I'd be interested to know what can raise
the interrupt.

Best regards,
Alexey