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

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Message-ID: <20240906061653.GC275077@black.fi.intel.com>
Date: Fri, 6 Sep 2024 09:16:53 +0300
From: Mika Westerberg <mika.westerberg@...ux.intel.com>
To: Kimriver Liu <kimriver.liu@...ngine.com>
Cc: jarkko.nikula@...ux.intel.com, andriy.shevchenko@...ux.intel.com,
	jsd@...ihalf.com, andi.shyti@...nel.org, linux-i2c@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] i2c: designware: fix master is holding SCL low while
 ENABLE bit is disabled

Hi,

On Fri, Sep 06, 2024 at 01:42:50PM +0800, Kimriver Liu wrote:
> It was observed 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 master is
> holding SCL low. If ENABLE bit is disabled, the software need
> enable it before trying to issue ABORT bit. otherwise,
> the controller ignores any write to ABORT bit
> 
> Signed-off-by: Kimriver Liu <kimriver.liu@...ngine.com>
> 
> ---
> 
> V3->V4:
>       1. update commit messages and add patch version and changelog
>       2. move print the error message in i2c_dw_xfer
> V2->V3: change (!enable) to (!(enable & DW_IC_ENABLE_ENABLE))
> V1->V2: used standard words in function names and addressed review comments
> 
> link to V1:
> https://lore.kernel.org/lkml/20240904064224.2394-1-kimriver.liu@siengine.com/
> ---
>  drivers/i2c/busses/i2c-designware-common.c | 12 ++++++++++
>  drivers/i2c/busses/i2c-designware-master.c | 27 ++++++++++++++++++++++
>  2 files changed, 39 insertions(+)
> 
> diff --git a/drivers/i2c/busses/i2c-designware-common.c b/drivers/i2c/busses/i2c-designware-common.c
> index e8a688d04aee..54acf8554582 100644
> --- a/drivers/i2c/busses/i2c-designware-common.c
> +++ b/drivers/i2c/busses/i2c-designware-common.c
> @@ -453,6 +453,18 @@ void __i2c_dw_disable(struct dw_i2c_dev *dev)
>  
>  	abort_needed = raw_intr_stats & DW_IC_INTR_MST_ON_HOLD;
>  	if (abort_needed) {
> +		if (!(enable & DW_IC_ENABLE_ENABLE)) {
> +			regmap_write(dev->map, DW_IC_ENABLE, DW_IC_ENABLE_ENABLE);
> +			enable |= DW_IC_ENABLE_ENABLE;
> +

Drop the empty line here.

> +			/*
> +			 * Wait two ic_clk delay when enabling the i2c to ensure ENABLE bit

i2c -> I2C

> +			 * is already set by the driver (for 400KHz this is 25us)
> +			 * as described in the DesignWare I2C databook.
> +			 */
> +			fsleep(25);
> +		}
> +
>  		regmap_write(dev->map, DW_IC_ENABLE, enable | DW_IC_ENABLE_ABORT);
>  		ret = regmap_read_poll_timeout(dev->map, DW_IC_ENABLE, enable,
>  					       !(enable & DW_IC_ENABLE_ABORT), 10,
> diff --git a/drivers/i2c/busses/i2c-designware-master.c b/drivers/i2c/busses/i2c-designware-master.c
> index c7e56002809a..6a053f3b5501 100644
> --- a/drivers/i2c/busses/i2c-designware-master.c
> +++ b/drivers/i2c/busses/i2c-designware-master.c
> @@ -253,6 +253,24 @@ static void i2c_dw_xfer_init(struct dw_i2c_dev *dev)
>  	__i2c_dw_write_intr_mask(dev, DW_IC_INTR_MASTER_MASK);
>  }
>  
> +static bool i2c_dw_is_master_idling(struct dw_i2c_dev *dev)
> +{
> +	u32 status;
> +	int ret;
> +
> +	regmap_read(dev->map, DW_IC_STATUS, &status);
> +	if (!(status & DW_IC_STATUS_MASTER_ACTIVITY))
> +		return true;
> +
> +	ret = regmap_read_poll_timeout(dev->map, DW_IC_STATUS, status,
> +			!(status & DW_IC_STATUS_MASTER_ACTIVITY),
> +			1100, 20000);
> +	if (ret)
> +		return false;
> +
> +	return true;

You can also do:

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


But this is already done in i2c_dw_wait_bus_not_busy() (reverse of this)
so perhaps consolidate them?

> +}
> +
>  static int i2c_dw_check_stopbit(struct dw_i2c_dev *dev)
>  {
>  	u32 val;
> @@ -788,6 +806,15 @@ i2c_dw_xfer(struct i2c_adapter *adap, struct i2c_msg msgs[], int num)
>  		goto done;
>  	}
>  
> +	/*
> +	 * This happens rarely 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.
> +	 */
> +	if (!i2c_dw_is_master_idling(dev))
> +		dev_err(dev->dev, "i2c master controller not idle\n");

i2c -> I2C

(the driver log messages are not too consistent though, something to
improve).

> +
>  	/*
>  	 * We must disable the adapter before returning and signaling the end
>  	 * of the current transfer. Otherwise the hardware might continue
> -- 
> 2.17.1