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

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Date:   Tue, 17 Oct 2017 10:52:28 +0200
From:   Cédric Le Goater <clg@...d.org>
To:     Andrea Scian - DAVE Embedded Systems <andrea.scian@...e.eu>
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>
Subject: Re: about pca955x led driver gpio management

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

Cheers,

C. 

> 
>>> My current kernel is quite old (4.1.15) but I've found Cédric patches on mainline and backported to this old revision.
>>>
>>> I'm facing an issue with it, because it seems that it fails when it's used in a mixed (led/gpios) environment.
>>>
>>> E.g.: let's say that I have one led connected to LED0 output and one GPIO connected at LED1 output.
>>>
>>> I define it as
>>>
>>>                          pca9551: pca9551@60 {
>>>                                  compatible = "nxp,pca9551";
>>>                                  reg = <0x60>;
>>>                                  #address-cells = <1>;
>>>                                  #size-cells = <0>;
>>>                                  #gpio-cells = <1>;
>>>
>>>                                  led@0 {
>>>                                          label = "led0";
>>>                                          reg = <0>;
>>>                                          linux,default-trigger = "none";
>>>                                  };
>>>                                  gpio@1 {
>>>                                          label = "gpio1";
>>>                                          reg = <1>;
>>>                                          type = <2>; /* GPIO */
>>>                                  };
>>>                  };
>>>
>>> At boot it's probed as
>>>
>>> root@...-lynx:~# dmesg | grep pca
>>> [    5.315425] leds-pca955x 5-0060: leds-pca955x: Using pca9551 8-bit LED driver at slave address 0x60
>>> [    5.350349] leds-pca955x 5-0060: gpios 511...511
>>>
>>> But I cannot access it:
>>>
>>> root@...-lynx:~# echo 511 > /sys/class/gpio/export
>>> -sh: echo: write error: Device or resource busy
>>>
>>> Because for pca955x_gpio_request_pin() this is at offset 0 (in fact is the first gpio registered of this gpio_chip) but it's the index 1 inside pca955x->leds[]
>>>
>>> Am I missing something? (maybe I made a mistake in my backport and/or I'm missing some patches about the GPIO subsystems).
>>>
>>> If I'm right I think I can send a patch to fix this (I'm thinking about having an array of GPIO index to map offset -> pca955x->leds[] index or just register all pins as GPIOs and then just report the busy state)
>>>
>>> WDYT?
>>>
>>> Kind Regards,
>>>
>