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

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Message-ID: <fpa7ufcpazewftgeoj72t3m7jumddvt23dzmqpr4znqx663yl7@4vckpbls2iyy>
Date: Thu, 12 Sep 2024 18:36:20 +0200
From: Andi Shyti <andi.shyti@...nel.org>
To: Andy Shevchenko <andy.shevchenko@...il.com>
Cc: Kimriver Liu <kimriver.liu@...ngine.com>, 
	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
Subject: Re: [PATCH v10] i2c: designware: fix controller is holding SCL low
 while ENABLE bit is disabled

On Thu, Sep 12, 2024 at 06:32:48PM GMT, Andy Shevchenko wrote:
> 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

/need/needs/

> > to enable it before trying to issue ABORT bit. otherwise,

/ABORT/the ABORT/

> > 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.

We could reword this to:

The patch fixes the issue where the controller cannot be disabled
while SCL is held low if the ENABLE bit is already disabled.

>   Fix the condition when controller cannot be disabled while SCL

/when/where/

>   is held low and ENABLE bit is already disabled.

/ENABLE/the ENABLE/

If you agree with the changes, I can apply them before merging.

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

Thanks a lot, Andy! I really appreciate your reviews!

> ...
> 
> > +		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/

I can fix it before merging.

> > + * 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)

I can fix it before merging.

Kimriver, if you agree, i can merge this and queue it for the
next week's fixes merge request.

Andi

> > +}
> 
> ...
> 
> > +	/*
> > +	 * 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
> 
>