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

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Message-ID: <Ztrr4-igQ20gu0VS@smile.fi.intel.com>
Date: Fri, 6 Sep 2024 14:47:47 +0300
From: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To: Kimriver Liu <kimriver.liu@...ngine.com>
Cc: jarkko.nikula@...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] i2c: designware: fix master is holding SCL low while
 ENABLE bit is disabled

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:

Nice, but the Subject (which is most important part) still has no versioning :-(

>       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

...

> +			/*
> +			 * 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);

And if we use 100kHz?
Please, calculate this delay based on the actual speed in use
(or about to be in use).

> +		}

-- 
With Best Regards,
Andy Shevchenko