linux-kernel - Re: [PATCH v7 4/9] i2c: rk3x: Move setting STATE_START and add STATE

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Date:	Fri, 6 May 2016 11:20:41 +0800
From:	"David.Wu" <david.wu@...k-chips.com>
To:	Doug Anderson <dianders@...omium.org>
Cc:	Heiko Stübner <heiko@...ech.de>,
	Wolfram Sang <wsa@...-dreams.de>,
	Mark Rutland <mark.rutland@....com>,
	Tao Huang <huangtao@...k-chips.com>,
	Jianqun Xu <xjq@...k-chips.com>, Lin Huang <hl@...k-chips.com>,
	Pawel Moll <pawel.moll@....com>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	"open list:ARM/Rockchip SoC..." <linux-rockchip@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Eddie Cai <cf@...k-chips.com>,
	Andy Shevchenko <andy.shevchenko@...il.com>,
	Rob Herring <robh+dt@...nel.org>,
	"linux-i2c@...r.kernel.org" <linux-i2c@...r.kernel.org>,
	Kumar Gala <galak@...eaurora.org>, Chris <zyw@...k-chips.com>,
	Brian Norris <briannorris@...gle.com>,
	David Riley <davidriley@...gle.com>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH v7 4/9] i2c: rk3x: Move setting STATE_START and add
 STATE_SETUP

Hi Doug,

在 2016/5/6 6:56, Doug Anderson 写道:
> David,
>
> On Wed, May 4, 2016 at 7:13 AM, David Wu <david.wu@...k-chips.com> wrote:
>> Signed-off-by: David Wu <david.wu@...k-chips.com>
>> ---
>> Change in v7:
>> - none
>>
>>   drivers/i2c/busses/i2c-rk3x.c | 5 ++++-
>>   1 file changed, 4 insertions(+), 1 deletion(-)
>
> Probably this change could be dropped now.  Switching the location of
> setting START_START was much more important when you were supporting
> HIGH SPEED mode.  I don't think we need it anymore, right?
>

Yes, I would drop it next version，STATE_SETUP didn't make sense, it was
not much more important, because there was a error printk for 
rk3x_i2c_setup() called failed.

> ...if we want to keep this change, I'd say:
>
> 1. Add a description, like maybe:
>
> To help with debugging add a STATE_SETUP between STATE_IDLE and
> STATE_START to make it more obvious that we're not actually idle but we
> also haven't initiated the start bit.  This change is not expected to
> have any impact but it does delay the changing of state to STATE_START.
> If previously we were getting an erroneous interrupt before we actually
> sent the start bit we'll now be treating that differently.  The new
> behavior (catching the erroneous interrupt) should be better.
>
> 2. Change "i2c->state = STATE_SETUP" to the _start_ of
> rk3x_i2c_setup().  That would have a better chance of catching a
> spurious interrupt.
>
> 3. Add an error check at the start of rk3x_i2c_irq() similar to the
> check for STATE_IDLE (or use the same check and modify the printk).
> Specifically the justification for adding STATE_SETUP is to help with
> debugging (catch interrupts that were unexpected and print more info
> about our state), so we should make it useful for this.
>
>
> -Doug
>
>
>