misc: Add support for the Arm Versatile Express config bus

Add support for the Arm Versatile Express config bus that is
being used for exposing various subsystems via a generic
configuration bus. This driver adds support for generating
transactions on this configuration bus and can be used by
other drivers to abstract the communication with the actual
function providers.

Signed-off-by: Liviu Dudau <liviu.dudau@foss.arm.com>
Reviewed-by: Heiko Schocher <hs@denx.de>

MAINTAINERS

@@ -287,6 +287,13 @@ F:	arch/arm/mach-uniphier/
 F:	configs/uniphier_*_defconfig
 N:	uniphier
 
+ARM VERSATILE EXPRESS DRIVERS
+M:	Liviu Dudau <liviu.dudau@foss.arm.com>
+S:	Maintained
+T:	git git://github.com/ARM-software/u-boot.git
+F:	drivers/misc/vexpress_config.c
+N:	vexpress
+
 ARM ZYNQ
 M:	Michal Simek <monstr@monstr.eu>
 S:	Maintained

drivers/misc/Kconfig

@@ -41,6 +41,14 @@ config ROCKCHIP_EFUSE
 	  extended (by porting the read function from the Linux kernel sources)
 	  to support other recent Rockchip devices.
 
+config VEXPRESS_CONFIG
+	bool "Enable support for Arm Versatile Express config bus"
+	depends on MISC
+	help
+	  If you say Y here, you will get support for accessing the
+	  configuration bus on the Arm Versatile Express boards via
+	  a sysreg driver.
+
 config CMD_CROS_EC
 	bool "Enable crosec command"
 	depends on CROS_EC

drivers/misc/Makefile

@@ -55,5 +55,6 @@ obj-$(CONFIG_STM32MP_FUSE) += stm32mp_fuse.o
 obj-$(CONFIG_SYS_DPAA_QBMAN) += fsl_portals.o
 obj-$(CONFIG_GDSYS_IOEP) += gdsys_ioep.o
 obj-$(CONFIG_GDSYS_RXAUI_CTRL) += gdsys_rxaui_ctrl.o
+obj-$(CONFIG_VEXPRESS_CONFIG) += vexpress_config.o
 obj-$(CONFIG_MPC83XX_SERDES) += mpc83xx_serdes.o
 obj-$(CONFIG_FS_LOADER) += fs_loader.o

drivers/misc/vexpress_config.c

@@ -0,0 +1,128 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Copyright (C) 2018 Arm Ltd
+ * Author: Liviu Dudau <liviu.dudau@foss.arm.com>
+ *
+ */
+#include <common.h>
+#include <dm.h>
+#include <dm/read.h>
+#include <asm/io.h>
+#include <linux/delay.h>
+#include <misc.h>
+
+#define SYS_CFGDATA		0xa0
+
+#define SYS_CFGCTRL		0xa4
+#define SYS_CFGCTRL_START	BIT(31)
+#define SYS_CFGCTRL_WRITE	BIT(30)
+
+#define SYS_CFGSTAT		0xa8
+#define SYS_CFGSTAT_ERR		BIT(1)
+#define SYS_CFGSTAT_COMPLETE	BIT(0)
+
+struct vexpress_config_sysreg {
+	phys_addr_t addr;
+	u32 site;
+};
+
+static int vexpress_config_exec(struct vexpress_config_sysreg *syscfg,
+				bool write, void *buf, int size)
+{
+	u32 cmd, status, tries = 100;
+
+	cmd = (*(u32 *)buf) | SYS_CFGCTRL_START | (syscfg->site << 16);
+
+	if (!write) {
+		/* write a canary in the data register for reads */
+		writel(0xdeadbeef, syscfg->addr + SYS_CFGDATA);
+	} else {
+		cmd |= SYS_CFGCTRL_WRITE;
+		writel(((u32 *)buf)[1], syscfg->addr + SYS_CFGDATA);
+	}
+	writel(0, syscfg->addr + SYS_CFGSTAT);
+	writel(cmd, syscfg->addr + SYS_CFGCTRL);
+
+	/* completion of command takes ages, go to sleep (150us) */
+	do {
+		udelay(150);
+		status = readl(syscfg->addr + SYS_CFGSTAT);
+		if (status & SYS_CFGSTAT_ERR)
+			return -EFAULT;
+	} while (--tries && !(status & SYS_CFGSTAT_COMPLETE));
+
+	if (!tries)
+		return -ETIMEDOUT;
+
+	if (!write)
+		(*(u32 *)buf) = readl(syscfg->addr + SYS_CFGDATA);
+
+	return 0;
+}
+
+static int vexpress_config_read(struct udevice *dev,
+				int offset, void *buf, int size)
+{
+	struct vexpress_config_sysreg *priv = dev_get_uclass_priv(dev);
+
+	if (size != sizeof(u32))
+		return -EINVAL;
+
+	return vexpress_config_exec(priv, false, buf, size);
+}
+
+static int vexpress_config_write(struct udevice *dev,
+				 int offset, const void *buf, int size)
+{
+	struct vexpress_config_sysreg *priv = dev_get_uclass_priv(dev);
+
+	if (size != sizeof(u32) * 2)
+		return -EINVAL;
+
+	return vexpress_config_exec(priv, true, (void *)buf, size);
+}
+
+static struct misc_ops vexpress_config_ops = {
+	.read = vexpress_config_read,
+	.write = vexpress_config_write,
+};
+
+static int vexpress_config_probe(struct udevice *dev)
+{
+	struct ofnode_phandle_args args;
+	struct vexpress_config_sysreg *priv;
+	const char *prop;
+	int err, prop_size;
+
+	err = dev_read_phandle_with_args(dev, "arm,vexpress,config-bridge",
+					 NULL, 0, 0, &args);
+	if (err)
+		return err;
+
+	prop = ofnode_get_property(args.node, "compatible", &prop_size);
+	if (!prop || (strncmp(prop, "arm,vexpress-sysreg", 19) != 0))
+		return -ENOENT;
+
+	priv = calloc(1, sizeof(*priv));
+	if (!priv)
+		return -ENOMEM;
+
+	dev->uclass_priv = priv;
+	priv->addr = ofnode_get_addr(args.node);
+
+	return dev_read_u32(dev, "arm,vexpress,site", &priv->site);
+}
+
+static const struct udevice_id vexpress_config_ids[] = {
+	{ .compatible = "arm,vexpress,config-bus" },
+	{ }
+};
+
+U_BOOT_DRIVER(vexpress_config_drv) = {
+	.name = "vexpress_config_bus",
+	.id = UCLASS_MISC,
+	.of_match = vexpress_config_ids,
+	.bind = dm_scan_fdt_dev,
+	.probe = vexpress_config_probe,
+	.ops = &vexpress_config_ops,
+};