linux-kernel - Re: about pca955x led driver gpio management

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Message-ID: <7c7304df-9a08-4343-8c73-da2d54436d77@dave.eu>
Date:   Wed, 25 Oct 2017 00:36:04 +0200
From:   Andrea Scian - DAVE Embedded Systems <andrea.scian@...e.eu>
To:     Cédric Le Goater <clg@...d.org>
Cc:     Bryan Wu <cooloney@...il.com>, Richard Purdie <rpurdie@...ys.net>,
        Jacek Anaszewski <j.anaszewski@...sung.com>,
        linux-leds@...r.kernel.org,
        linux-kernel <linux-kernel@...r.kernel.org>,
        Andrew Jeffery <andrew@...id.au>
Subject: Re: about pca955x led driver gpio management


Il 24/10/2017 07:51, Cédric Le Goater ha scritto:
> On 10/17/2017 11:16 AM, Andrea Scian - DAVE Embedded Systems wrote:
>>
>>> On 10/17/2017 10:20 AM, Andrea Scian - DAVE Embedded Systems wrote:
>>>>
>>>> Il 17/10/2017 10:18, Cédric Le Goater ha scritto:
>>>>> On 10/17/2017 09:36 AM, Andrea Scian - DAVE Embedded Systems wrote:
>>>>>> Dear all,
>>>>>>
>>>>>> I'm working on an iMX6 based board with a PCA9555 which is used both to drive LEDs and manage some GPIOs.
>>>>> The PCA9555 chip and the PCA955[0-3] chips have different control
>>>>> registers. You need a different led driver for it.
>>>>
>>>> My typo sorry, as you can see in the device tree below, I'm using pca9551
>>>
>>> ok.
>>>
>>> You might want to take a look at how we mixed gpios and leds on the witherspoon
>>> system using pca9552 chips. we added a gpio-leds binding.
>>>
>>> https://github.com/openbmc/linux/blob/dev-4.10/arch/arm/boot/dts/aspeed-bmc-opp-witherspoon.dts
>>
>> understood: you configure all pins of PCA955x as GPIOs and the map the one you need as led with gpio-leds binding.
> 
> Sorry I got distracted.
> 
>> However to me this is a kind of workaround or, at least, there's nothing about this limitation into the devicetree binding (in fact, IMHO, the device tree binding example will just fail)
> 
> euh ? what do you mean. There is a real system using this device tree.
> I think we would know about it if it didn't work. Please explain
> 

I mean that, for what I understand, your configuration is working 
because all pin of 9551 are configured as GPIOs (and the binded back as led)
In my configuration I have some pins configured as led and some as 
GPIOs, and this is not working.

>> I wrote the attached patch which should fix the issue and allow a more generic approach. WDYT?
>>
>> (in case it looks good, I'll send the patch in the correct way)
> 
> Please send the patch to discuss, add Andrew Jeffery <andrew@...id.au>
> in cc:
> 

Sorry for the delay but I'm busy in Prague with OSSummit and ELCE. I'll 
send a proper patch and more comments, if needed, by the begin of next week.

(BTW, if some of you are here, drop me a line and have a beer together! 
;-) )