[PATCH 4/5] sysinfo: Add gpio-sysinfo driver

[Sean Anderson]

On 3/1/21 3:46 PM, Sean Anderson wrote:
> This uses the newly-added dm_gpio_get_values_as_int_base3 function to
> implement a sysinfo device. The revision map is stored in the device tree.
> 
> Signed-off-by: Sean Anderson <sean.anderson at seco.com>
> ---
> 
>   .../sysinfo/gpio-sysinfo.txt                  |  37 +++++
>   drivers/sysinfo/Kconfig                       |   8 +
>   drivers/sysinfo/Makefile                      |   1 +
>   drivers/sysinfo/gpio.c                        | 138 ++++++++++++++++++
>   4 files changed, 184 insertions(+)
>   create mode 100644 doc/device-tree-bindings/sysinfo/gpio-sysinfo.txt
>   create mode 100644 drivers/sysinfo/gpio.c
> 
> diff --git a/doc/device-tree-bindings/sysinfo/gpio-sysinfo.txt b/doc/device-tree-bindings/sysinfo/gpio-sysinfo.txt
> new file mode 100644
> index 0000000000..b5739d94e9
> --- /dev/null
> +++ b/doc/device-tree-bindings/sysinfo/gpio-sysinfo.txt
> @@ -0,0 +1,37 @@
> +GPIO-based Sysinfo device
> +
> +This binding describes several GPIOs which specify a board revision. Each GPIO
> +forms a digit in a ternary revision number. This revision is then mapped to a
> +name using the revisions and names properties.
> +
> +Each GPIO may be floating, pulled-up, or pulled-down, mapping to digits 2, 1,
> +and 0, respectively. The first GPIO forms the least-significant digit of the
> +revision. For example, consider the property
> +
> +	gpios = <&gpio 0>, <&gpio 1>, <&gpio 2>;
> +
> +If GPIO 0 is pulled-up, GPIO 1 is pulled-down, and GPIO 2 is floating, then the
> +revision would be
> +
> +	0t201 = 2*9 + 0*3 + 1*3 = 19
> +
> +If instead GPIO 0 is floating, GPIO 1 is pulled-up, and GPIO 2 is pulled-down,
> +then the revision would be
> +
> +	0t012 = 0*9 + 1*3 + 2*1 = 5
> +
> +Required properties:
> +- compatible: should be "gpio-sysinfo".
> +- gpios: should be a list of gpios forming the revision number,
> +  least-significant-digit first
> +- revisions: a list of known revisions; any revisions not present will have the
> +  name "unknown"
> +- names: the name of each revision in revisions
> +
> +Example:
> +sysinfo {
> +	compatible = "gpio-sysinfo";
> +	gpios = <&gpio_a 15>, <&gpio_a 16>, <&gpio_a 17>;
> +	revisions = <19>, <5>;
> +	names = "rev_a", "foo";
> +};
> diff --git a/drivers/sysinfo/Kconfig b/drivers/sysinfo/Kconfig
> index 85c1e81e41..381dcd8844 100644
> --- a/drivers/sysinfo/Kconfig
> +++ b/drivers/sysinfo/Kconfig
> @@ -30,4 +30,12 @@ config SYSINFO_SMBIOS
>   	  one which provides a way to specify this SMBIOS information in the
>   	  devicetree, without needing any board-specific functionality.
>   
> +config SYSINFO_GPIO
> +	bool "Enable gpio sysinfo driver"
> +	help
> +	  Support querying gpios to determine board revision. This uses gpios to
> +	  form a ternary number (when they are pulled-up, -down, or floating).
> +	  This ternary number is then mapped to a board revision name using
> +	  device tree properties.
> +
>   endif
> diff --git a/drivers/sysinfo/Makefile b/drivers/sysinfo/Makefile
> index 6d04fcba1d..d9f708b7ea 100644
> --- a/drivers/sysinfo/Makefile
> +++ b/drivers/sysinfo/Makefile
> @@ -4,5 +4,6 @@
>   # Mario Six,  Guntermann & Drunck GmbH, mario.six at gdsys.cc
>   obj-y += sysinfo-uclass.o
>   obj-$(CONFIG_SYSINFO_GAZERBEAM) += gazerbeam.o
> +obj-$(CONFIG_SYSINFO_GPIO) += gpio.o
>   obj-$(CONFIG_SYSINFO_SANDBOX) += sandbox.o
>   obj-$(CONFIG_SYSINFO_SMBIOS) += smbios.o
> diff --git a/drivers/sysinfo/gpio.c b/drivers/sysinfo/gpio.c
> new file mode 100644
> index 0000000000..6a0eff3ec9
> --- /dev/null
> +++ b/drivers/sysinfo/gpio.c
> @@ -0,0 +1,138 @@
> +// SPDX-License-Identifier: GPL-2.0+
> +/*
> + * Copyright (C) 2021 Sean Anderson <sean.anderson at seco.com>
> + */
> +
> +#include <common.h>
> +#include <dm.h>
> +#include <dm/device_compat.h>
> +#include <log.h>
> +#include <sysinfo.h>
> +#include <asm/gpio.h>
> +
> +struct sysinfo_gpio_priv {
> +	struct gpio_desc *gpios;
> +	int gpio_num, revision;
> +};
> +
> +static int sysinfo_gpio_detect(struct udevice *dev)
> +{
> +	struct sysinfo_gpio_priv *priv = dev_get_priv(dev);
> +
> +	priv->revision = dm_gpio_get_values_as_int_base3(priv->gpios,
> +							 priv->gpio_num);
> +	return priv->revision < 0 ? priv->revision : 0;
> +}
> +
> +static int sysinfo_gpio_get_int(struct udevice *dev, int id, int *val)
> +{
> +	struct sysinfo_gpio_priv *priv = dev_get_priv(dev);
> +
> +	switch (id) {
> +	case SYSINFO_ID_REVISION:
> +		if (priv->revision < 0) {

Looks like I forgot to remove this brace. Will be fixed in v2.

--Sean

> +			return priv->revision;
> +		*val = priv->revision;
> +		return 0;
> +	default:
> +		return -EINVAL;
> +	};
> +}
> +
> +static int sysinfo_gpio_get_str(struct udevice *dev, int id, size_t size, char *val)
> +{
> +	struct sysinfo_gpio_priv *priv = dev_get_priv(dev);
> +
> +	switch (id) {
> +	case SYSINFO_ID_REVISION: {
> +		const char *name = NULL;
> +		int i, ret;
> +		u32 revision;
> +
> +		if (priv->revision < 0)
> +			return priv->revision;
> +
> +		for (i = 0; i < priv->gpio_num; i++) {
> +			ret = dev_read_u32_index(dev, "revisions", i,
> +						 &revision);
> +			if (ret) {
> +				if (ret != -EOVERFLOW)
> +					return ret;
> +				break;
> +			}
> +
> +			if (revision == priv->revision) {
> +				ret = dev_read_string_index(dev, "names", i,
> +							    &name);
> +				if (ret < 0)
> +					return ret;
> +				break;
> +			}
> +		}
> +		if (!name)
> +			name = "unknown";
> +
> +		strncpy(val, name, size);
> +		val[size - 1] = '\0';
> +		return 0;
> +	} default:
> +		return -EINVAL;
> +	};
> +}
> +
> +static const struct sysinfo_ops sysinfo_gpio_ops = {
> +	.detect = sysinfo_gpio_detect,
> +	.get_int = sysinfo_gpio_get_int,
> +	.get_str = sysinfo_gpio_get_str,
> +};
> +
> +static int sysinfo_gpio_probe(struct udevice *dev)
> +{
> +	int ret;
> +	struct sysinfo_gpio_priv *priv = dev_get_priv(dev);
> +
> +	priv->gpio_num = gpio_get_list_count(dev, "gpios");
> +	if (priv->gpio_num < 0) {
> +		dev_err(dev, "could not get gpios length (err = %d)\n",
> +			priv->gpio_num);
> +		return priv->gpio_num;
> +	}
> +
> +	priv->gpios = calloc(priv->gpio_num, sizeof(*priv->gpios));
> +	if (!priv->gpios) {
> +		dev_err(dev, "could not allocate memory for %d gpios\n",
> +			priv->gpio_num);
> +		return -ENOMEM;
> +	}
> +
> +	ret = gpio_request_list_by_name(dev, "gpios", priv->gpios,
> +					priv->gpio_num, GPIOD_IS_IN);
> +	if (ret != priv->gpio_num) {
> +		dev_err(dev, "could not get gpios (err = %d)\n",
> +			priv->gpio_num);
> +		return ret;
> +	}
> +
> +	if (!dev_read_bool(dev, "revisions") || !dev_read_bool(dev, "names")) {
> +		dev_err(dev, "revisions or names properties missing\n");
> +		return -ENOENT;
> +	}
> +
> +	priv->revision = -ENOENT;
> +
> +	return 0;
> +}
> +
> +static const struct udevice_id sysinfo_gpio_ids[] = {
> +	{ .compatible = "gpio-sysinfo" },
> +	{ /* sentinel */ }
> +};
> +
> +U_BOOT_DRIVER(sysinfo_gpio) = {
> +	.name           = "sysinfo_gpio",
> +	.id             = UCLASS_SYSINFO,
> +	.of_match       = sysinfo_gpio_ids,
> +	.ops		= &sysinfo_gpio_ops,
> +	.priv_auto	= sizeof(struct sysinfo_gpio_priv),
> +	.probe          = sysinfo_gpio_probe,
> +};
>