From: Graeme Smecher <gsmecher@threespeedlogic.com>
To: Linus Walleij <linus.walleij@linaro.org>
Cc: Haojian Zhuang <haojian.zhuang@gmail.com>,
"linux-gpio@vger.kernel.org" <linux-gpio@vger.kernel.org>,
gregory.clement@free-electrons.com
Subject: Re: [PATCH] gpio: pca953x: Don't flip bits on PCA957x GPIO expanders when probing them.
Date: Mon, 23 Sep 2013 09:36:39 -0400 [thread overview]
Message-ID: <524043E7.2050803@threespeedlogic.com> (raw)
In-Reply-To: <CACRpkdYWCFCtmF2_ORA5RRJudeNm9u+6ngMfcW8xrc+K2-Y3TQ@mail.gmail.com>
Hi,
On 23/09/13 06:57 AM, Linus Walleij wrote:
> On Fri, Sep 13, 2013 at 11:41 PM, Graeme Smecher
> <gsmecher@threespeedlogic.com> wrote:
>
>> The pca957x driver supports a handful of I2C GPIO expanders from NXP, Maxim,
>> and TI. For the PCA9574 and PCA9575 devices only, the driver resets the GPIO
>> level and direction in the pca957x_probe function. This seems like the wrong
>> thing to do, since it can cause hardware bit twiddles during warm reboots when
>> the chip state and reset values don't match.
>>
>> This kind of initialization is best left upstream (in a bootloader) or
>> downstream (in userspace). It's also an inconsistency across devices supported
>> by this driver.
>>
>> This patch is NOT boot-tested: the SoC I'm using is stuck on 2.6.37, and the
>> patch doesn't apply trivially.
>>
>> Signed-off-by: Graeme Smecher<gsmecher@threespeedlogic.com>
>> Acked-by: Haojian Zhuang<haojian.zhuang@gmail.com>
> Patch applied with Gregory's Tested-by tag!
Thanks all!
cheers,
Graeme
prev parent reply other threads:[~2013-09-23 13:39 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-09-13 21:41 [PATCH] gpio: pca953x: Don't flip bits on PCA957x GPIO expanders when probing them Graeme Smecher
2013-09-20 20:24 ` Linus Walleij
2013-09-20 20:37 ` Gregory CLEMENT
2013-09-20 21:06 ` Linus Walleij
2013-09-23 9:51 ` Gregory CLEMENT
2013-09-23 10:57 ` Linus Walleij
2013-09-23 13:36 ` Graeme Smecher [this message]
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