回复: [PATCH] i2c: designware: fix master is holding SCL low while ENABLE bit is disabled

[Liu Kimriver/刘金河]

Hi 
  I am sorry for not replying to questions in time on Friday.


-----邮件原件-----
发件人: Mika Westerberg <mika.westerberg@xxxxxxxxxxxxxxx> 
发送时间: 2024年9月6日 16:08
收件人: Liu Kimriver/刘金河 <kimriver.liu@xxxxxxxxxxxx>
抄送: jarkko.nikula@xxxxxxxxxxxxxxx; andriy.shevchenko@xxxxxxxxxxxxxxx; jsd@xxxxxxxxxxxx; andi.shyti@xxxxxxxxxx; linux-i2c@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx
主题: Re: [PATCH] i2c: designware: fix master is holding SCL low while ENABLE bit is disabled

Hi,

On Fri, Sep 06, 2024 at 03:47:31PM +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@xxxxxxxxxxxx>
> 
> ---
> V5->V6: restore i2c_dw_is_master_idling() function checking
> V4->V5: delete master idling checking
> 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@xxxxxxxxxxxx/
> ---
>  drivers/i2c/busses/i2c-designware-common.c | 11 +++++++++++
>  drivers/i2c/busses/i2c-designware-master.c | 22 ++++++++++++++++++++++
>  2 files changed, 33 insertions(+)
> 
> diff --git a/drivers/i2c/busses/i2c-designware-common.c b/drivers/i2c/busses/i2c-designware-common.c
> index e8a688d04aee..2b3398cd4382 100644
> --- a/drivers/i2c/busses/i2c-designware-common.c
> +++ b/drivers/i2c/busses/i2c-designware-common.c
> @@ -453,6 +453,17 @@ 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;
> +			/*
> +			 * Wait two ic_clk delay when enabling the I2C to ensure ENABLE bit
> +			 * 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..132b7237c004 100644
> --- a/drivers/i2c/busses/i2c-designware-master.c
> +++ b/drivers/i2c/busses/i2c-designware-master.c
> @@ -253,6 +253,19 @@ 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;
> +
> +	regmap_read(dev->map, DW_IC_STATUS, &status);
> +	if (!(status & DW_IC_STATUS_MASTER_ACTIVITY))
> +		return true;
> +
> +	return !regmap_read_poll_timeout(dev->map, DW_IC_STATUS, status,
> +			!(status & DW_IC_STATUS_MASTER_ACTIVITY),
> +			1100, 20000);
> +}

>Yeah, I now realize that i2c_dw_wait_bus_not_busy() checks for
>DW_IC_STATUS_ACTIVITY not for DW_IC_STATUS_MASTER_ACTIVITY as I thought
>so consolidating them makes not that much sense.

>This looks good to me,

Thanks.
 This case happens rarely and is hard to reproduce. We reproduce this issue 
 in RTL simulation. It is necessary to add waiting DW_IC_STATUS_MASTER_ACTIVITY
 idling before disabling I2C when I2C transfer completed.  as described in the
 DesignWare I2C databook(Flowchart for DW_apb_i2c Controller)


-----------------
Best Regards
Kimriver Liu