This adds some support into fdtdec for reading GPIO definitions from
the fdt. We permit up to FDT_GPIO_MAX GPIOs in the system. Each GPIO
is of the form:
gpio-function-name = <phandle gpio_num flags>;
where:
phandle is a pointer to the GPIO node
gpio_num is the number of the GPIO (0 to 223)
flags is a flag, as follows:
bit meaning
0 0=polarity normal, 1=active low (inverted)
An example is:
enable-propounder-gpios = <&gpio 43 0>;
which means that GPIO 43 is used to enable the propounder (setting the
GPIO high), or that you can detect that the propounder is enabled by
checking if the GPIO is high (the fdt does not indicate input/output).
Two main functions are provided:
fdtdec_decode_gpio() reads a GPIO property from an fdt node and decodes it
into a structure.
fdtdec_setup_gpio() sets up the GPIO by calling gpio_request for you.
Both functions can cope with the property being missing, which is taken to
mean that that GPIO function is not available or is not needed.
[For reference, from Stephen Warren <swarren@nvidia.com>. It may be that
we add this extra complexity later if needed:
The correct way to parse such a GPIO property in general is:
* Read the first cell.
* Find the node referenced by the phandle (the controller).
* Ensure property gpio-controller is present in the controller node.
* Read property #gpio-cells from the controller node.
* Extract #gpio-cells from the original property.
* Keep processing more cells from the original property; there may be
multiple GPIOs listed.
According to the binding documentation in the Linux kernel, Samsung
Exynos4 doesn't use this format, and while all other chips do have a
flags cell, about 50% of the controllers indicate the cell is unused.
]
Signed-off-by: Simon Glass <sjg@chromium.org>
Signed-off-by: Tom Warren <twarren@nvidia.com>
Add a function to look up a property which is a phandle in a node, and
another to read a fixed-length integer array from an fdt property.
Also add a function to read boolean properties, although there is no
actual boolean type in U-Boot.
Signed-off-by: Simon Glass <sjg@chromium.org>
Acked-by: Gerald Van Baren <vanbaren@cideas.com>
Acked-by: Stephen Warren <swarren@nvidia.com>
Signed-off-by: Tom Warren <twarren@nvidia.com>
This fixes five trivial issues in fdtdec.c:
1. fdtdec_get_is_enabled() doesn't really need a default value
2. The fdt must be word-aligned, since otherwise it will fail on ARM
3. The compat_names[] array is missing its first element. This is needed
only because the first fdt_compat_id is defined to be invalid.
4. Added a header prototype for fdtdec_next_compatible()
5. Change fdtdec_next_alias() to only increment its 'upto' parameter
on success, to make the display error messages in the caller easier.
Signed-off-by: Simon Glass <sjg@chromium.org>
Acked-by: Gerald Van Baren <vanbaren@cideas.com>
Acked-by: Stephen Warren <swarren@nvidia.com>
Signed-off-by: Tom Warren <twarren@nvidia.com>
Stephen Warren pointed out that we should use nodes whether or not they
have an alias in the /aliases section. The aliases section specifies the
order so far as it can, but is not essential. Operating without alisses
is useful when the enumerated order of nodes does not matter (admittedly
rare in U-Boot).
This is considerably more complex, and it is important to keep this
complexity out of driver code. This patch creates a function
fdtdec_find_aliases() which returns an ordered list of node offsets
for a particular compatible ID, taking account of alias nodes.
Signed-off-by: Simon Glass <sjg@chromium.org>
Signed-off-by: Tom Warren <twarren@nvidia.com>
This library provides useful functions to drivers which want to use
the fdt to control their operation. Functions are provided to:
- look up and enumerate a device type (for example assigning i2c bus 0,
i2c bus 1, etc.)
- decode basic types from the fdt, like addresses and integers
While this library is not strictly necessary, it helps to minimise the
changes to a driver, in order to make it work under fdt control. Less
code is required, and so the barrier to switch drivers over is lower.
Additional functions to read arrays and GPIOs could be made available
here also.
Signed-off-by: Simon Glass <sjg@chromium.org>
Simon Glass