soc: aspeed: Miscellaneous control interfaces

The ASPEED BMC SoCs have many knobs and switches that are sometimes
design-specific and often defy any approach to unify them under an
existing subsystem.

Add a driver to translate a devicetree table into sysfs entries to
expose bits and fields for manipulation from userspace. This encompasses
concepts from scratch registers to boolean conditions to enable or
disable host interface features.

OpenBMC-Staging-Count: 5
Signed-off-by: Andrew Jeffery <andrew@aj.id.au>
Signed-off-by: Joel Stanley <joel@jms.id.au>

5 files changed, 204 insertions, 0 deletions

diff --git a/drivers/soc/Kconfig b/drivers/soc/Kconfig
index c07b4a85253f..b750a88547c7 100644
--- a/drivers/soc/Kconfig
+++ b/drivers/soc/Kconfig
@@ -2,6 +2,7 @@ menu "SOC (System On Chip) specific Drivers"
 
 source "drivers/soc/actions/Kconfig"
 source "drivers/soc/amlogic/Kconfig"
+source "drivers/soc/aspeed/Kconfig"
 source "drivers/soc/atmel/Kconfig"
 source "drivers/soc/bcm/Kconfig"
 source "drivers/soc/fsl/Kconfig"
diff --git a/drivers/soc/Makefile b/drivers/soc/Makefile
index 90b686e586c6..eb473f48df3c 100644
--- a/drivers/soc/Makefile
+++ b/drivers/soc/Makefile
@@ -4,6 +4,7 @@
 #
 
 obj-$(CONFIG_ARCH_ACTIONS)	+= actions/
+obj-$(CONFIG_ARCH_ASPEED)       += aspeed/
 obj-$(CONFIG_ARCH_AT91)		+= atmel/
 obj-y				+= bcm/
 obj-$(CONFIG_ARCH_DOVE)		+= dove/
diff --git a/drivers/soc/aspeed/Kconfig b/drivers/soc/aspeed/Kconfig
new file mode 100644
index 000000000000..704a4efe180f
--- /dev/null
+++ b/drivers/soc/aspeed/Kconfig
@@ -0,0 +1,11 @@
+menu "ASPEED SoC drivers"
+
+config ASPEED_BMC_MISC
+	bool "Miscellaneous ASPEED BMC interfaces"
+	depends on ARCH_ASPEED || COMPILE_TEST
+	default ARCH_ASPEED
+	help
+	  Say yes to expose VGA and LPC scratch registers, and other
+	  miscellaneous control interfaces specific to the ASPEED BMC SoCs
+
+endmenu
diff --git a/drivers/soc/aspeed/Makefile b/drivers/soc/aspeed/Makefile
new file mode 100644
index 000000000000..d1a80f9a584f
--- /dev/null
+++ b/drivers/soc/aspeed/Makefile
@@ -0,0 +1 @@
+obj-$(CONFIG_ASPEED_BMC_MISC) += aspeed-bmc-misc.o
diff --git a/drivers/soc/aspeed/aspeed-bmc-misc.c b/drivers/soc/aspeed/aspeed-bmc-misc.c
new file mode 100644
index 000000000000..314007bad74f
--- /dev/null
+++ b/drivers/soc/aspeed/aspeed-bmc-misc.c
@@ -0,0 +1,190 @@
+// SPDX-License-Identifier: GPL-2.0+
+// Copyright 2018 IBM Corp.
+
+#include <linux/kobject.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+#include <linux/regmap.h>
+#include <linux/mfd/syscon.h>
+
+#define DEVICE_NAME "aspeed-bmc-misc"
+
+struct aspeed_bmc_ctrl {
+	const char *name;
+	u32 offset;
+	u32 mask;
+	u32 shift;
+	struct regmap *map;
+	struct kobj_attribute attr;
+};
+
+struct aspeed_bmc_misc {
+	struct device *dev;
+	struct regmap *map;
+	struct aspeed_bmc_ctrl *ctrls;
+	int nr_ctrls;
+};
+
+static int aspeed_bmc_misc_parse_dt_child(struct device_node *child,
+					  struct aspeed_bmc_ctrl *ctrl)
+{
+	int rc;
+
+	/* Example child:
+	 *
+	 * ilpc2ahb {
+	 *     offset = <0x80>;
+	 *     bit-mask = <0x1>;
+	 *     bit-shift = <6>;
+	 *     label = "foo";
+	 * }
+	 */
+	if (of_property_read_string(child, "label", &ctrl->name))
+		ctrl->name = child->name;
+
+	rc = of_property_read_u32(child, "offset", &ctrl->offset);
+	if (rc < 0)
+		return rc;
+
+	rc = of_property_read_u32(child, "bit-mask", &ctrl->mask);
+	if (rc < 0)
+		return rc;
+
+	rc = of_property_read_u32(child, "bit-shift", &ctrl->shift);
+	if (rc < 0)
+		return rc;
+
+	ctrl->mask <<= ctrl->shift;
+
+	return 0;
+}
+
+static int aspeed_bmc_misc_parse_dt(struct aspeed_bmc_misc *bmc,
+				    struct device_node *parent)
+{
+	struct aspeed_bmc_ctrl *ctrl;
+	struct device_node *child;
+	int rc;
+
+	bmc->nr_ctrls = of_get_child_count(parent);
+	bmc->ctrls = devm_kcalloc(bmc->dev, bmc->nr_ctrls, sizeof(*bmc->ctrls),
+				  GFP_KERNEL);
+	if (!bmc->ctrls)
+		return -ENOMEM;
+
+	ctrl = bmc->ctrls;
+	for_each_child_of_node(parent, child) {
+		rc = aspeed_bmc_misc_parse_dt_child(child, ctrl++);
+		if (rc < 0) {
+			of_node_put(child);
+			return rc;
+		}
+	}
+
+	return 0;
+}
+
+static ssize_t aspeed_bmc_misc_show(struct kobject *kobj,
+				    struct kobj_attribute *attr, char *buf)
+{
+	struct aspeed_bmc_ctrl *ctrl;
+	unsigned int val;
+	int rc;
+
+	ctrl = container_of(attr, struct aspeed_bmc_ctrl, attr);
+	rc = regmap_read(ctrl->map, ctrl->offset, &val);
+	if (rc)
+		return rc;
+
+	val &= ctrl->mask;
+	val >>= ctrl->shift;
+
+	return sprintf(buf, "%u\n", val);
+}
+
+static ssize_t aspeed_bmc_misc_store(struct kobject *kobj,
+				     struct kobj_attribute *attr,
+				     const char *buf, size_t count)
+{
+	struct aspeed_bmc_ctrl *ctrl;
+	long val;
+	int rc;
+
+	rc = kstrtol(buf, 0, &val);
+	if (rc)
+		return rc;
+
+	ctrl = container_of(attr, struct aspeed_bmc_ctrl, attr);
+	val <<= ctrl->shift;
+	rc = regmap_update_bits(ctrl->map, ctrl->offset, ctrl->mask, val);
+
+	return rc < 0 ? rc : count;
+}
+
+static int aspeed_bmc_misc_add_sysfs_attr(struct aspeed_bmc_misc *bmc,
+					  struct aspeed_bmc_ctrl *ctrl)
+{
+	ctrl->map = bmc->map;
+
+	sysfs_attr_init(&ctrl->attr.attr);
+	ctrl->attr.attr.name = ctrl->name;
+	ctrl->attr.attr.mode = 0664;
+	ctrl->attr.show = aspeed_bmc_misc_show;
+	ctrl->attr.store = aspeed_bmc_misc_store;
+
+	return sysfs_create_file(&bmc->dev->kobj, &ctrl->attr.attr);
+}
+
+static int aspeed_bmc_misc_populate_sysfs(struct aspeed_bmc_misc *bmc)
+{
+	int rc;
+	int i;
+
+	for (i = 0; i < bmc->nr_ctrls; i++) {
+		rc = aspeed_bmc_misc_add_sysfs_attr(bmc, &bmc->ctrls[i]);
+		if (rc < 0)
+			return rc;
+	}
+
+	return 0;
+}
+
+static int aspeed_bmc_misc_probe(struct platform_device *pdev)
+{
+	struct aspeed_bmc_misc *bmc;
+	int rc;
+
+	bmc = devm_kzalloc(&pdev->dev, sizeof(*bmc), GFP_KERNEL);
+	if (!bmc)
+		return -ENOMEM;
+
+	bmc->dev = &pdev->dev;
+	bmc->map = syscon_node_to_regmap(pdev->dev.parent->of_node);
+	if (IS_ERR(bmc->map))
+		return PTR_ERR(bmc->map);
+
+	rc = aspeed_bmc_misc_parse_dt(bmc, pdev->dev.of_node);
+	if (rc < 0)
+		return rc;
+
+	return aspeed_bmc_misc_populate_sysfs(bmc);
+}
+
+static const struct of_device_id aspeed_bmc_misc_match[] = {
+	{ .compatible = "aspeed,bmc-misc" },
+	{ },
+};
+
+static struct platform_driver aspeed_bmc_misc = {
+	.driver = {
+		.name		= DEVICE_NAME,
+		.of_match_table = aspeed_bmc_misc_match,
+	},
+	.probe = aspeed_bmc_misc_probe,
+};
+
+module_platform_driver(aspeed_bmc_misc);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Andrew Jeffery <andrew@aj.id.au>");