[U-Boot] [PATCH v3] misc: Add support for the Arm Versatile Express config bus

[Liviu Dudau]

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 at foss.arm.com>
Reviewed-by: Heiko Schocher <hs at denx.de>
---

Changelog:
 - v3: Added MAINTAINERS entry and Reviewed-by tag
 - v2: removed #define DEBUG line leftover

 MAINTAINERS                    |   7 ++
 drivers/misc/Kconfig           |   8 +++
 drivers/misc/Makefile          |   1 +
 drivers/misc/vexpress_config.c | 128 +++++++++++++++++++++++++++++++++
 4 files changed, 144 insertions(+)
 create mode 100644 drivers/misc/vexpress_config.c

diff --git a/MAINTAINERS b/MAINTAINERS
index ea21d59f1e..613d7b29a0 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -286,6 +286,13 @@ F:	arch/arm/mach-uniphier/
 F:	configs/uniphier_*_defconfig
 N:	uniphier
 
+ARM VERSATILE EXPRESS DRIVERS
+M:	Liviu Dudau <liviu.dudau at 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 at monstr.eu>
 S:	Maintained
diff --git a/drivers/misc/Kconfig b/drivers/misc/Kconfig
index bfa5c91687..78dc9264f9 100644
--- a/drivers/misc/Kconfig
+++ b/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
diff --git a/drivers/misc/Makefile b/drivers/misc/Makefile
index da4666fdfc..50b52f9aa5 100644
--- a/drivers/misc/Makefile
+++ b/drivers/misc/Makefile
@@ -55,4 +55,5 @@ 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
diff --git a/drivers/misc/vexpress_config.c b/drivers/misc/vexpress_config.c
new file mode 100644
index 0000000000..9f5baa5288
--- /dev/null
+++ b/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 at 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,
+};
-- 
2.18.0