linux-kernel - Re: [PATCH v10] i2c: designware: fix controller is holding SCL low while ENABLE bit is disabled

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Message-ID: <ZuMJoHWLU1FIznZR@surfacebook.localdomain>
Date: Thu, 12 Sep 2024 18:32:48 +0300
From: Andy Shevchenko <andy.shevchenko@...il.com>
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,
	andi.shyti@...nel.org, linux-i2c@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v10] i2c: designware: fix controller is holding SCL low
 while ENABLE bit is disabled

Thu, Sep 12, 2024 at 02:11:12PM +0800, Kimriver Liu kirjoitti:
> It was observed that issuing ABORT bit (IC_ENABLE[1]) will not
> work when IC_ENABLE is already disabled.
> 
> Check if ENABLE bit (IC_ENABLE[0]) is disabled when the controller
> is holding SCL low. If ENABLE bit is disabled, the software need
> to enable it before trying to issue 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 can be fix the controller cannot be disabled while
> SCL is held low in ENABLE bit is already disabled.

There are English words but a complete nonsense together.

  Fix the condition when controller cannot be disabled while SCL
  is held low and ENABLE bit is already disabled.

Reviewed-by: Andy Shevchenko <andy@...nel.org>

...

> +		if (!(enable & DW_IC_ENABLE_ENABLE)) {
> +			regmap_write(dev->map, DW_IC_ENABLE, DW_IC_ENABLE_ENABLE);
> +			/*
> +			 * Wait 10 times the signaling period of the highest I2C
> +			 * transfer supported by the driver (for 400KHz this is
> +			 * 25us) to ensure the I2C ENABLE bit is already set
> +			 * as described in the DesignWare I2C databook.
> +			 */
> +			fsleep(DIV_ROUND_CLOSEST_ULL(10 * MICRO, t->bus_freq_hz));

> +			/* Keep ENABLE bit is already set before Setting ABORT.*/

			/* Set ENABLE bit before setting ABORT */


> +			enable |= DW_IC_ENABLE_ENABLE;
> +		}

...

> +/*
> + * This functions waits controller idling before disabling I2C

s/functions/function/

> + * 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.
> + */
> +static bool i2c_dw_is_controller_active(struct dw_i2c_dev *dev)
> +{
> +	u32 status;
> +
> +	regmap_read(dev->map, DW_IC_STATUS, &status);
> +	if (!(status & DW_IC_STATUS_MASTER_ACTIVITY))
> +		return false;
> +
> +	return regmap_read_poll_timeout(dev->map, DW_IC_STATUS, status,
> +				       !(status & DW_IC_STATUS_MASTER_ACTIVITY),
> +					1100, 20000) != 0;

	return regmap_read_poll_timeout(dev->map, DW_IC_STATUS, status,
					!(status & DW_IC_STATUS_MASTER_ACTIVITY),
					1100, 20000) != 0;

(in the second line replaced 7 spaces by a single TAB to fix the indentation)

> +}

...

> +	/*
> +	 * This happens rarely (~1:500) and is hard to reproduce. Debug trace
> +	 * showed that IC_STATUS had value of 0x23 when STOP_DET occurred,
> +	 * if disable IC_ENABLE.ENABLE immediately that can result in
> +	 * IC_RAW_INTR_STAT.MASTER_ON_HOLD holding SCL low. Check if
> +	 * controller is still ACTIVE before disabling I2C.
> +	 */
> +	if (i2c_dw_is_controller_active(dev))
> +		dev_err(dev->dev, "controller active\n");

-- 
With Best Regards,
Andy Shevchenko