linux-kernel - Re: [PATCH v2 3/4] i2c: imx: Simplify stopped state tracking

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Message-ID: <87zhxuo9o1.fsf@gmail.com>
Date:   Fri, 10 Aug 2018 11:25:34 +0200
From:   Esben Haabendal <esben.haabendal@...il.com>
To:     Uwe Kleine-König <u.kleine-koenig@...gutronix.de>
Cc:     linux-i2c@...r.kernel.org,
        Wolfram Sang <wsa+renesas@...g-engineering.com>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Yuan Yao <yao.yuan@...escale.com>,
        Philipp Zabel <p.zabel@...gutronix.de>,
        Phil Reid <preid@...ctromag.com.au>,
        Lucas Stach <l.stach@...gutronix.de>,
        Clemens Gruber <clemens.gruber@...ruber.com>,
        Peter Rosin <peda@...ntia.se>,
        Fabio Estevam <fabio.estevam@....com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 3/4] i2c: imx: Simplify stopped state tracking

Uwe Kleine-König <u.kleine-koenig@...gutronix.de> writes:

> On Thu, Aug 09, 2018 at 02:06:43PM +0200, Esben Haabendal wrote:
>> Uwe Kleine-König <u.kleine-koenig@...gutronix.de> writes:
>> 
>> > On Mon, Jul 09, 2018 at 11:43:03AM +0200, Esben Haabendal wrote:
>> >> From: Esben Haabendal <eha@...f.com>
>> >> 
>> >> Always update the stopped state when busy status have been checked.
>> >> This is identical to what was done before, with the exception of error
>> >> handling.
>> >> Without this change, some errors cause the stopped state to be left in
>> >> incorrect state in i2c_imx_stop(), i2c_imx_dma_read(), i2c_imx_read() and
>> >> i2c_imx_xfer().
>> >> 
>> >> Signed-off-by: Esben Haabendal <eha@...f.com>
>> >> ---
>> >>  drivers/i2c/busses/i2c-imx.c | 12 ++++++------
>> >>  1 file changed, 6 insertions(+), 6 deletions(-)
>> >> 
>> >> diff --git a/drivers/i2c/busses/i2c-imx.c b/drivers/i2c/busses/i2c-imx.c
>> >> index d86f152176a4..1db8e6790afc 100644
>> >> --- a/drivers/i2c/busses/i2c-imx.c
>> >> +++ b/drivers/i2c/busses/i2c-imx.c
>> >> @@ -421,10 +421,14 @@ static int i2c_imx_bus_busy(struct imx_i2c_struct *i2c_imx, int for_busy)
>> >>  			return -EAGAIN;
>> >>  		}
>> >>  
>> >> -		if (for_busy && (temp & I2SR_IBB))
>> >> +		if (for_busy && (temp & I2SR_IBB)) {
>> >> +			i2c_imx->stopped = 0;
>> >>  			break;
>> >> -		if (!for_busy && !(temp & I2SR_IBB))
>> >> +		}
>> >> +		if (!for_busy && !(temp & I2SR_IBB)) {
>> >> +			i2c_imx->stopped = 1;
>> >>  			break;
>> >> +		}
>> >
>> > Would it make sense to assign to ->stopped independent of for_busy?
>> 
>> What do you mean?
>> 
>> Assigning to ->stopped on each check for I2SR_IBB in loop, independent
>> of the for_busy argument?  I don't think so.  The additional assignments
>> would be to the same value as it is set to already.
>
> Currently you have:
>
> 	if (for_busy && (temp & I2SR_IBB)) {
> 		i2c_imx->stopped = 0;
> 		break;
> 	}
>
> 	if (!for_busy && !(temp & I2SR_IBB)) {
> 		i2c_imx->stopped = 1;
> 		break;
> 	}
>
> The semantic of this is the same (apart from always updating .stopped)
> but is imho easier:
>
> 	i2c_imx->stopped = !(temp & I2SR_IBB);
>
> 	if (for_busy != i2c_imx->stopped)
> 		break;

Yes, that should work also.
Shorter, but IMHO a bit more convoluted to read.
Let me know if I should send a new version with this change.

/Esben