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SubjectRe: [PATCH mfd+gpio 1/2] drivers: mfd: Add support for Moxtet bus
On Thu, 30 Aug 2018, Marek Behún wrote:

> On the Turris Mox router there can be connected different modules to
> the main CPU board, currently a module with a SFP cage, a module with
> MiniPCIe connector, a 4-port switch module and a 8-port switch module,
> for example:
> [CPU]-[PCIe]-[8-port switch]-[8-port switch]-[SFP]
>
> Each of this modules has an input and output shift register, and these
> are connected via SPI to CPU board.
>
> Via this SPI connection we are able to discover which modules are
> connected and we can also read/write some configuration to the modules.
> Fromi/to each module 8 bits can be read (of which lower 4 bits identify
> the module) and written.
>
> For example from the module with a SFP cage we can read the LOS,
> TX-FAULT and MOD-DEF0 signals, while we can write TX-DISABLE and
> RATE-SELECT signals.
>
> Other modules may support something else.
>
> This driver creates a new bus type, called "moxtet". For each Mox module
> it finds via SPI, it creates a new device on the moxtet bus so that
> drivers can be written for them, for example a gpio driver for the
> module with a SFP cage.
>
> The topology of how Mox modules are connected can then be read by
> listing /sys/bus/moxtet/devices.
>
> Signed-off-by: Marek Behún <marek.behun@nic.cz>
> ---
> Documentation/devicetree/bindings/mfd/moxtet.txt | 36 ++

This should be supplied in a separate patch.

> MAINTAINERS | 7 +

As above please.

> drivers/mfd/Kconfig | 10 +
> drivers/mfd/Makefile | 1 +
> drivers/mfd/moxtet.c | 501 +++++++++++++++++++++++
> include/linux/mfd/moxtet.h | 103 +++++
> 6 files changed, 658 insertions(+)
> create mode 100644 Documentation/devicetree/bindings/mfd/moxtet.txt
> create mode 100644 drivers/mfd/moxtet.c
> create mode 100644 include/linux/mfd/moxtet.h
>
> diff --git a/Documentation/devicetree/bindings/mfd/moxtet.txt b/Documentation/devicetree/bindings/mfd/moxtet.txt
> new file mode 100644
> index 000000000000..02b96fbd5ddd
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/mfd/moxtet.txt
> @@ -0,0 +1,36 @@
> +Turris Mox module configuration bus (over SPI)
> +
> +Required properties:
> + - compatible : Should be "cznic,moxtet".
> + - #address-cells : Has to be 1
> + - #size-cells : Has to be 0
> +For other required and optional properties of SPI slave
> +nodes please refer to ../spi/spi-bus.txt.

This line is cut unnecessarily short.

> +Required properties of subnodes:
> + - reg : Should be position on the Moxtet bus
> + - moxtet,id : Should be ID of the Moxtet device connected

What is this used for?

> +The driver finds the devices connected to the bus by itself, but it may be
> +needed to reference some of them from other parts of the device tree. In that
> +case the devices can be defined as subnodes of the moxtet node.
> +
> +Example:
> +
> + moxtet@1 {

Does the device itself have a address, or is it only contactable via
SPI?

> + #address-cells = <1>;
> + #size-cells = <0>;
> + compatible = "cznic,moxtet";
> + reg = <1>;
> + spi-max-frequency = <1000000>;
> + spi-cpol;
> + spi-cpha;
> +
> + moxtet_sfp: moxtet-sfp@0 {
> + compatible = "cznic,moxtet-sfp";
> + gpio-controller;
> + #gpio-cells;
> + reg = <0>;
> + moxtet,id = <1>;
> + }
> + };
> diff --git a/MAINTAINERS b/MAINTAINERS
> index a5b256b25905..84e60ee83951 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -1412,6 +1412,13 @@ F: drivers/clocksource/timer-prima2.c
> F: drivers/clocksource/timer-atlas7.c
> N: [^a-z]sirf
>
> +ARM/CZ.NIC TURRIS MOX SUPPORT
> +M: Marek Behun <marek.behun@nic.cz>
> +W: http://mox.turris.cz
> +S: Maintained
> +F: include/mfd/moxtet.h
> +F: drivers/mfd/moxtet.c
> +
> ARM/EBSA110 MACHINE SUPPORT
> M: Russell King <linux@armlinux.org.uk>
> L: linux-arm-kernel@lists.infradead.org (moderated for non-subscribers)
> diff --git a/drivers/mfd/Kconfig b/drivers/mfd/Kconfig
> index 11841f4b7b2b..cb401841e2ac 100644
> --- a/drivers/mfd/Kconfig
> +++ b/drivers/mfd/Kconfig
> @@ -814,6 +814,16 @@ config MFD_MAX8998
> additional drivers must be enabled in order to use the functionality
> of the device.
>
> +config MFD_MOXTET
> + tristate "CZ.NIC Turris Mox module configuration bus"
> + depends on SPI_MASTER && OF
> + help
> + Say yes here to add support for the module configuration bus found
> + on CZ.NIC's Turris Mox. This is needed for the ability to read
> + in what order the modules are connected and to get/set some of
> + their settings. For example the GPIOs on Mox SFP module are
> + configured through this bus.
> +
> config MFD_MT6397
> tristate "MediaTek MT6397 PMIC Support"
> select MFD_CORE
> diff --git a/drivers/mfd/Makefile b/drivers/mfd/Makefile
> index 5856a9489cbd..338ecf311911 100644
> --- a/drivers/mfd/Makefile
> +++ b/drivers/mfd/Makefile
> @@ -159,6 +159,7 @@ max8925-objs := max8925-core.o max8925-i2c.o
> obj-$(CONFIG_MFD_MAX8925) += max8925.o
> obj-$(CONFIG_MFD_MAX8997) += max8997.o max8997-irq.o
> obj-$(CONFIG_MFD_MAX8998) += max8998.o max8998-irq.o
> +obj-$(CONFIG_MFD_MOXTET) += moxtet.o
>
> pcf50633-objs := pcf50633-core.o pcf50633-irq.o
> obj-$(CONFIG_MFD_PCF50633) += pcf50633.o
> diff --git a/drivers/mfd/moxtet.c b/drivers/mfd/moxtet.c
> new file mode 100644
> index 000000000000..1cd1a62002e7
> --- /dev/null
> +++ b/drivers/mfd/moxtet.c
> @@ -0,0 +1,501 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Turris Mox module configuration bus driver
> + *
> + * Copyright (C) 2018 Marek Behun <marek.behun@nic.cz>
> + */
> +
> +#include <linux/module.h>
> +#include <linux/mutex.h>
> +#include <linux/of_device.h>
> +#include <linux/spi/spi.h>
> +#include <linux/mfd/moxtet.h>

Alphabetical please.

Right, I can probably save us a both a great deal of time here and
tell you right off of the bat that this is not an MFD. MFDs will
either use the MFD API or something like of_platform_populate().

Glancing over the reminder of the driver, it looks like an alternative
of MFD or at least MFD-like. I think drivers/platform would be a
better fit.

--
Lee Jones [李琼斯]
Linaro Services Technical Lead
Linaro.org │ Open source software for ARM SoCs
Follow Linaro: Facebook | Twitter | Blog

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