linux-kernel - Re: [PATCH v11] i2c: designware: fix controller is holding SCL low while ENABLE bit is disabled

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Message-ID: <hua4cnnstss2lw5ejau25ktdiujwz3m3ixawnfuz7havwsr7vc@i7jlayooy3ha>
Date: Fri, 20 Sep 2024 10:52:23 +0200
From: Andi Shyti <andi.shyti@...nel.org>
To: Kimriver Liu <kimriver.liu@...ngine.com>
Cc: jarkko.nikula@...ux.intel.com, andriy.shevchenko@...ux.intel.com, 
	mika.westerberg@...ux.intel.com, jsd@...ihalf.com, linux-i2c@...r.kernel.org, 
	linux-kernel@...r.kernel.org, Andy Shevchenko <andy@...nel.org>
Subject: Re: [PATCH v11] i2c: designware: fix controller is holding SCL low
 while ENABLE bit is disabled

Hi Kimriver,

On Fri, Sep 13, 2024 at 11:31:46AM GMT, Kimriver Liu wrote:
> It was observed that issuing the ABORT bit (IC_ENABLE[1]) will not
> work when IC_ENABLE is already disabled.
> 
> Check if the ENABLE bit (IC_ENABLE[0]) is disabled when the controller
> is holding SCL low. If the ENABLE bit is disabled, the software needs
> to enable it before trying to issue the ABORT bit. otherwise,
> the controller ignores any write to ABORT bit.
> 
> These kernel logs show up whenever an I2C transaction is
> attempted after this failure.
> i2c_designware e95e0000.i2c: timeout waiting for bus ready
> i2c_designware e95e0000.i2c: timeout in disabling adapter
> 
> The patch fixes the issue where the controller cannot be disabled
> while SCL is held low if the ENABLE bit is already disabled.
> 
> Fixes: 2409205acd3c ("i2c: designware: fix __i2c_dw_disable() in case master is holding SCL low")
> Signed-off-by: Kimriver Liu <kimriver.liu@...ngine.com>
> Reviewed-by: Mika Westerberg <mika.westerberg@...ux.intel.com>
> Acked-by: Jarkko Nikula <jarkko.nikula@...ux.intel.com>
> Reviewed-by: Andy Shevchenko <andy@...nel.org>

I'm sorry for the delay, but I needed to wait for the previous
batch of fixes to be merged.

[...]

> +/*
> + * This function waits controller idling before disabling I2C
> + * When the controller is not in the IDLE state,
> + * MST_ACTIVITY bit (IC_STATUS[5]) is set.
> + * Values:
> + * 0x1 (ACTIVE): Controller not idle
> + * 0x0 (IDLE): Controller is idle
> + * The function is called after returning the end of the current transfer
> + * Returns:
> + * False when controller is in IDLE state.
> + * True when controller is in ACTIVE state.
> + */

I took the liberty of making some small changes to the comment:

+/*
+ * This function waits for the controller to be idle before disabling I2C
+ * When the controller is not in the IDLE state, the MST_ACTIVITY bit
+ * (IC_STATUS[5]) is set.
+ *
+ * Values:
+ * 0x1 (ACTIVE): Controller not idle
+ * 0x0 (IDLE): Controller is idle
+ *
+ * The function is called after completing the current transfer.
+ *
+ * Returns:
+ * False when the controller is in the IDLE state.
+ * True when the controller is in the ACTIVE state.
+ */

for an improved clarity and address a few grammatical issues.
Please verify that it's correct.

I merged your patch to i2c/i2c-host-fixes along with the latest 
changes proposed by Andy.

Thanks for your work,
Andi