sysinfo: Add gpio-sysinfo driver

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@seco.com>
Reviewed-by: Simon Glass <sjg@chromium.org>

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";
+};

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

drivers/sysinfo/Makefile

@@ -4,5 +4,6 @@
 # Mario Six,  Guntermann & Drunck GmbH, mario.six@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

drivers/sysinfo/gpio.c

@@ -0,0 +1,141 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Copyright (C) 2021 Sean Anderson <sean.anderson@seco.com>
+ */
+
+#include <common.h>
+#include <dm.h>
+#include <log.h>
+#include <sysinfo.h>
+#include <asm/gpio.h>
+#include <dm/device_compat.h>
+
+/**
+ * struct sysinfo_gpio_priv - GPIO sysinfo private data
+ * @gpios: List of GPIOs used to detect the revision
+ * @gpio_num: The number of GPIOs in @gpios
+ * @revision: The revision as detected from the GPIOs.
+ */
+struct sysinfo_gpio_priv {
+	struct gpio_desc *gpios;
+	int gpio_num, revision;
+};
+
+static int sysinfo_gpio_detect(struct udevice *dev)
+{
+	int ret;
+	struct sysinfo_gpio_priv *priv = dev_get_priv(dev);
+
+	ret = dm_gpio_get_values_as_int_base3(priv->gpios, priv->gpio_num);
+	if (ret < 0)
+		return ret;
+
+	priv->revision = ret;
+	return 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_BOARD_MODEL:
+		*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_BOARD_MODEL: {
+		const char *name = NULL;
+		int i, ret;
+		u32 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;
+	}
+
+	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,
+};