Re: [PATCH v3 05/16] mfd: Add support for Kontron sl28cpld management controller

Michael Walle
2020-05-11T22:29:53Z

Am 2020-05-11 23:44, schrieb Michael Walle:
> Am 2020-05-11 23:13, schrieb Rob Herring:
>> On Thu, Apr 23, 2020 at 07:45:32PM +0200, Michael Walle wrote:
>>> This patch adds core support for the board management controller
>>> found
>>> on the SMARC-sAL28 board. It consists of the following functions:
>>> - watchdog
>>> - GPIO controller
>>> - PWM controller
>>> - fan sensor
>>> - interrupt controller
>>>
>>> At the moment, this controller is used on the Kontron SMARC-sAL28
>>> board.
>>>
>>> Please note that the MFD driver is defined as bool in the Kconfig
>>> because the next patch will add interrupt support.
>>>
>>> Signed-off-by: Michael Walle <michael@walle.cc>
>>> ---
>>> drivers/mfd/Kconfig | 19 +++++
>>> drivers/mfd/Makefile | 2 +
>>> drivers/mfd/sl28cpld.c | 153
>>> +++++++++++++++++++++++++++++++++++++++++
>>> 3 files changed, 174 insertions(+)
>>> create mode 100644 drivers/mfd/sl28cpld.c
>>>
>>> diff --git a/drivers/mfd/Kconfig b/drivers/mfd/Kconfig
>>> index 0a59249198d3..be0c8d93c526 100644
>>> --- a/drivers/mfd/Kconfig
>>> +++ b/drivers/mfd/Kconfig
>>> @@ -2060,5 +2060,24 @@ config SGI_MFD_IOC3
>>> If you have an SGI Origin, Octane, or a PCI IOC3 card,
>>> then say Y. Otherwise say N.
>>>
>>> +config MFD_SL28CPLD
>>> + bool "Kontron sl28 core driver"
>>> + depends on I2C=y
>>> + depends on OF
>>> + select REGMAP_I2C
>>> + select MFD_CORE
>>> + help
>>> + This option enables support for the board management controller
>>> + found on the Kontron sl28 CPLD. You have to select individual
>>> + functions, such as watchdog, GPIO, etc, under the corresponding
>>> menus
>>> + in order to enable them.
>>> +
>>> + Currently supported boards are:
>>> +
>>> + Kontron SMARC-sAL28
>>> +
>>> + To compile this driver as a module, choose M here: the module
>>> will be
>>> + called sl28cpld.
>>> +
>>> endmenu
>>> endif
>>> diff --git a/drivers/mfd/Makefile b/drivers/mfd/Makefile
>>> index f935d10cbf0f..9bc38863b9c7 100644
>>> --- a/drivers/mfd/Makefile
>>> +++ b/drivers/mfd/Makefile
>>> @@ -259,3 +259,5 @@ obj-$(CONFIG_MFD_ROHM_BD718XX) += rohm-bd718x7.o
>>> obj-$(CONFIG_MFD_STMFX) += stmfx.o
>>>
>>> obj-$(CONFIG_SGI_MFD_IOC3) += ioc3.o
>>> +
>>> +obj-$(CONFIG_MFD_SL28CPLD) += sl28cpld.o
>>> diff --git a/drivers/mfd/sl28cpld.c b/drivers/mfd/sl28cpld.c
>>> new file mode 100644
>>> index 000000000000..1e5860cc7ffc
>>> --- /dev/null
>>> +++ b/drivers/mfd/sl28cpld.c
>>> @@ -0,0 +1,153 @@
>>> +// SPDX-License-Identifier: GPL-2.0-only
>>> +/*
>>> + * MFD core for the sl28cpld.
>>> + *
>>> + * Copyright 2019 Kontron Europe GmbH
>>> + */
>>> +
>>> +#include <linux/i2c.h>
>>> +#include <linux/interrupt.h>
>>> +#include <linux/kernel.h>
>>> +#include <linux/mfd/core.h>
>>> +#include <linux/module.h>
>>> +#include <linux/of_platform.h>
>>> +#include <linux/regmap.h>
>>> +
>>> +#define SL28CPLD_VERSION 0x03
>>> +#define SL28CPLD_WATCHDOG_BASE 0x04
>>> +#define SL28CPLD_HWMON_FAN_BASE 0x0b
>>> +#define SL28CPLD_PWM0_BASE 0x0c
>>> +#define SL28CPLD_PWM1_BASE 0x0e
>>> +#define SL28CPLD_GPIO0_BASE 0x10
>>> +#define SL28CPLD_GPIO1_BASE 0x15
>>> +#define SL28CPLD_GPO_BASE 0x1a
>>> +#define SL28CPLD_GPI_BASE 0x1b
>>> +#define SL28CPLD_INTC_BASE 0x1c
>>
>> If you want to use 'reg' in the binding, these are the numbers you
>> should be using rather than making up numbering!
>
> My motivation is that I don't want to hardcode the internal addresses
> of the management controller in the device tree. For example if they
> will move around with a later update of the controller, so a driver can
> be compatible with both the old and the new version. If they are in the
> device tree, only one register layout is possible.
>
>> However, I still don't think you need any child nodes. All the data in
>> the DT binding is right here in the driver already. There's no
>> advantage
>> to putting child nodes in DT, because this driver still has to be
>> updated if you add more nodes.
>
> But then any phandle will reference the mfd device. And for example
> there
> are two different interrupt controllers, that is the INTC and the
> GPIO[01],
> which will then be combined into one device tree node, right?
>
> So the mfd node would be
>
> cpld: sl28cpld@4a {
> interrupt-controller;
> #interrupt-cells = <2>;
> gpio-controller;
> #gpio-cells = <2>;
> [..]
> };
>
> and then depending on the mapping one could use:
>
> interrupts-extended = <&cpld 0 FLAGS>; /* gpio0 line 0 */
> interrupts-extended = <&cpld 8 FLAGS>; /* gpio1 line 0 */
> interrupts-extended = <&cpld 12 FLAGS>; /* irq0 */
>
> gpios = <&cpld 0> /* gpio0 line 0 */
>
> But there is also offset 12, but then it is the GPI controller:
>
> gpios = <&cpld 12> /* gpi line 0, nothing to do with irq0 */
>
> I don't know if this is good practice, I guess you have to tell me. And
> is it possible to combine any sub device into the mfd node in that way?

Oh I don't think that will work for the watchdog. If you just have one
watchdog it just looks odd.

cpld: sl28cpld@4a {
interrupt-controller;
#interrupt-cells = <2>;
gpio-controller;
#gpio-cells = <2>;
timeout-sec = <10>; /* watchdog property */
};

And won't pass the dtbindings check because the nodename is not
"watchdog(@[0-9]+)?". But it really falls short if you want to have
two watchdogs with different properties.

-michael