device + util/sconfig: introduce new device `gpio`

Introduce a new device `gpio` that is going to be used for generic
abstraction of gpio operations in the devicetree.

The general idea behind this is that every chip can have gpios that
shall be accessible in a very generic way by any driver through the
devicetree.

The chip that implements the chip-specific gpio operations has to assign
them to the generic device operations struct, which then gets assigned
to the gpio device during device probing. See CB:48583 for how this gets
done for the SoCs using intelblocks/gpio.

The gpio device then can be added to the devicetree with an alias name
like in the following example:

  chip soc/whateverlake
    device gpio 0 alias soc_gpio on end
    ...
  end

Any driver that requires access to this gpio device needs to have a
device pointer (or multiple) and an option for specifying the gpio to be
used in its chip config like this:

  struct drivers_ipmi_config {
    ...
    DEVTREE_CONST struct device *gpio_dev;
    u16 post_complete_gpio;
    ...
  };

The device `soc_gpio` can then be linked to the chip driver's `gpio_dev`
above by using the syntax `use ... as ...`, which was introduced in
commit 8e1ea52:

  chip drivers/ipmi
    use soc_gpio as gpio_dev
    register "bmc_jumper_gpio" = "GPP_D22"
    ...
  end

The IPMI driver can then use the generic gpio operations without any
knowlege of the chip's specifics:

  unsigned int gpio_val;
  const struct gpio_operations *gpio_ops;
  gpio_ops = dev_get_gpio_ops(conf->gpio_dev);
  gpio_val = gpio_ops->get(conf->bmc_jumper_gpio);

For a full example have a look at CB:48096 and CB:48095.

This change adds the new device type to sconfig and adds generic gpio
operations to the `device_operations` struct. Also, a helper for getting
the gpio operations from a device after checking them for NULL pointers
gets added.

Successfully tested on Supermicro X11SSM-F with CB:48097, X11SSH-TF with
CB:48711 and OCP DeltaLake with CB:48672.

Change-Id: Ic4572ad8b37bd1afd2fb213b2c67fb8aec536786
Tested-by: Johnny Lin <Johnny_Lin@wiwynn.com>
Tested-by: Michael Niewöhner <foss@mniewoehner.de>
Tested-by: Patrick Rudolph <siro@das-labor.org>
Signed-off-by: Michael Niewöhner <foss@mniewoehner.de>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/48582
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Nico Huber <nico.h@gmx.de>

0 files changed, 0 insertions, 0 deletions