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

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

[Alexey Charkov]

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.

Signed-off-by: Alexey Charkov <alchark@flipper.net>
---
 drivers/i2c/busses/i2c-rk3x.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/drivers/i2c/busses/i2c-rk3x.c b/drivers/i2c/busses/i2c-rk3x.c
index fcede9f6ed54..dbf1ed30fda6 100644
--- a/drivers/i2c/busses/i2c-rk3x.c
+++ b/drivers/i2c/busses/i2c-rk3x.c
@@ -1125,6 +1125,16 @@ static int rk3x_i2c_xfer_common(struct i2c_adapter *adap,
 		}
 	}
 
+	/*
+	 * Do not leave the controller enabled between transfers. It keeps
+	 * tracking the bus while enabled, and if the lines collapse under it,
+	 * e.g. as an unpowered target clamps them, its state machine wedges
+	 * driving SDA low until it is disabled. This also gets it out of
+	 * whatever state it was stuck in when a transfer timed out.
+	 */
+	val = i2c_readl(i2c, REG_CON) & REG_CON_TUNING_MASK;
+	i2c_writel(i2c, val, REG_CON);
+
 	clk_disable(i2c->pclk);
 	clk_disable(i2c->clk);
 

---
base-commit: d419d682257d813f6cb7a28e42b35d0edf4ad038
change-id: 20261015-i2c-rk3x-disable-24672d4f38bb

Best regards,
--  
Alexey Charkov <alchark@flipper.net>

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

[Shawn Lin]

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);



> Signed-off-by: Alexey Charkov <alchark@flipper.net>
> ---
>   drivers/i2c/busses/i2c-rk3x.c | 10 ++++++++++
>   1 file changed, 10 insertions(+)
> 
> diff --git a/drivers/i2c/busses/i2c-rk3x.c b/drivers/i2c/busses/i2c-rk3x.c
> index fcede9f6ed54..dbf1ed30fda6 100644
> --- a/drivers/i2c/busses/i2c-rk3x.c
> +++ b/drivers/i2c/busses/i2c-rk3x.c
> @@ -1125,6 +1125,16 @@ static int rk3x_i2c_xfer_common(struct i2c_adapter *adap,
>   		}
>   	}
>   
> +	/*
> +	 * Do not leave the controller enabled between transfers. It keeps
> +	 * tracking the bus while enabled, and if the lines collapse under it,
> +	 * e.g. as an unpowered target clamps them, its state machine wedges
> +	 * driving SDA low until it is disabled. This also gets it out of
> +	 * whatever state it was stuck in when a transfer timed out.
> +	 */
> +	val = i2c_readl(i2c, REG_CON) & REG_CON_TUNING_MASK;
> +	i2c_writel(i2c, val, REG_CON);
> +
>   	clk_disable(i2c->pclk);
>   	clk_disable(i2c->clk);
>   
> 
> ---
> base-commit: d419d682257d813f6cb7a28e42b35d0edf4ad038
> change-id: 20261015-i2c-rk3x-disable-24672d4f38bb
> 
> Best regards,
> --
> Alexey Charkov <alchark@flipper.net>
> 
> 
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