x86: Add SCU IPC driver for Intel MID platforms

Intel MID platforms have few microcontrollers inside SoC, one of them
is so called System Controller Unit (SCU).

Here is the driver to communicate with microcontroller.

Signed-off-by: Vincent Tinelli <vincent.tinelli@intel.com>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Acked-by: Simon Glass <sjg@chromium.org>

arch/x86/Kconfig

@@ -83,6 +83,8 @@ endchoice
 # subarchitectures-specific options below
 config INTEL_MID
 	bool "Intel MID platform support"
+	select REGMAP
+	select SYSCON
 	help
 	  Select to build a U-Boot capable of supporting Intel MID
 	  (Mobile Internet Device) platform systems which do not have

arch/x86/include/asm/cpu.h

@@ -54,6 +54,7 @@ enum {
 	X86_NONE,
 	X86_SYSCON_ME,		/* Intel Management Engine */
 	X86_SYSCON_PINCONF,	/* Intel x86 pin configuration */
+	X86_SYSCON_SCU,		/* System Controller Unit */
 };
 
 struct cpuid_result {

arch/x86/include/asm/scu.h

@@ -0,0 +1,28 @@
+/*
+ * Copyright (c) 2017 Intel Corporation
+ *
+ * SPDX-License-Identifier:	GPL-2.0+
+ */
+#ifndef _X86_ASM_SCU_IPC_H_
+#define _X86_ASM_SCU_IPC_H_
+
+/* IPC defines the following message types */
+#define IPCMSG_WARM_RESET	0xf0
+#define IPCMSG_COLD_RESET	0xf1
+#define IPCMSG_SOFT_RESET	0xf2
+#define IPCMSG_COLD_BOOT	0xf3
+#define IPCMSG_GET_FW_REVISION	0xf4
+#define IPCMSG_WATCHDOG_TIMER	0xf8	/* Set Kernel Watchdog Threshold */
+
+struct ipc_ifwi_version {
+	u16	minor;
+	u8	major;
+	u8	hardware_id;
+	u32	reserved[3];
+};
+
+/* Issue commands to the SCU with or without data */
+int scu_ipc_simple_command(u32 cmd, u32 sub);
+int scu_ipc_command(u32 cmd, u32 sub, u32 *in, int inlen, u32 *out, int outlen);
+
+#endif	/* _X86_ASM_SCU_IPC_H_ */

arch/x86/lib/Makefile

@@ -32,6 +32,7 @@ obj-y	+= pirq_routing.o
 obj-y	+= relocate.o
 obj-y += physmem.o
 obj-$(CONFIG_X86_RAMTEST) += ramtest.o
+obj-$(CONFIG_INTEL_MID) += scu.o
 obj-y	+= sections.o
 obj-y += sfi.o
 obj-y	+= string.o

arch/x86/lib/scu.c

@@ -0,0 +1,168 @@
+/*
+ * Copyright (c) 2017 Intel Corporation
+ *
+ * Intel Mobile Internet Devices (MID) based on Intel Atom SoCs have few
+ * microcontrollers inside to do some auxiliary tasks. One of such
+ * microcontroller is System Controller Unit (SCU) which, in particular,
+ * is servicing watchdog and controlling system reset function.
+ *
+ * This driver enables IPC channel to SCU.
+ *
+ * SPDX-License-Identifier:	GPL-2.0+
+ */
+#include <common.h>
+#include <dm.h>
+#include <regmap.h>
+#include <syscon.h>
+#include <asm/cpu.h>
+#include <asm/scu.h>
+#include <linux/errno.h>
+#include <linux/io.h>
+#include <linux/kernel.h>
+
+/* SCU register map */
+struct ipc_regs {
+	u32 cmd;
+	u32 status;
+	u32 sptr;
+	u32 dptr;
+	u32 reserved[28];
+	u32 wbuf[4];
+	u32 rbuf[4];
+};
+
+struct scu {
+	struct ipc_regs *regs;
+};
+
+/**
+ * scu_ipc_send_command() - send command to SCU
+ * @regs: register map of SCU
+ * @cmd: command
+ *
+ * Command Register (Write Only):
+ * A write to this register results in an interrupt to the SCU core processor
+ * Format:
+ * |rfu2(8) | size(8) | command id(4) | rfu1(3) | ioc(1) | command(8)|
+ */
+static void scu_ipc_send_command(struct ipc_regs *regs, u32 cmd)
+{
+	writel(cmd, &regs->cmd);
+}
+
+/**
+ * scu_ipc_check_status() - check status of last command
+ * @regs: register map of SCU
+ *
+ * Status Register (Read Only):
+ * Driver will read this register to get the ready/busy status of the IPC
+ * block and error status of the IPC command that was just processed by SCU
+ * Format:
+ * |rfu3(8)|error code(8)|initiator id(8)|cmd id(4)|rfu1(2)|error(1)|busy(1)|
+ */
+static int scu_ipc_check_status(struct ipc_regs *regs)
+{
+	int loop_count = 100000;
+	int status;
+
+	do {
+		status = readl(&regs->status);
+		if (!(status & BIT(0)))
+			break;
+
+		udelay(1);
+	} while (--loop_count);
+	if (!loop_count)
+		return -ETIMEDOUT;
+
+	if (status & BIT(1)) {
+		printf("%s() status=0x%08x\n", __func__, status);
+		return -EIO;
+	}
+
+	return 0;
+}
+
+static int scu_ipc_cmd(struct ipc_regs *regs, u32 cmd, u32 sub,
+		       u32 *in, int inlen, u32 *out, int outlen)
+{
+	int i, err;
+
+	for (i = 0; i < inlen; i++)
+		writel(*in++, &regs->wbuf[i]);
+
+	scu_ipc_send_command(regs, (inlen << 16) | (sub << 12) | cmd);
+	err = scu_ipc_check_status(regs);
+
+	if (!err) {
+		for (i = 0; i < outlen; i++)
+			*out++ = readl(&regs->rbuf[i]);
+	}
+
+	return err;
+}
+
+/**
+ * scu_ipc_simple_command() - send a simple command
+ * @cmd: command
+ * @sub: sub type
+ *
+ * Issue a simple command to the SCU. Do not use this interface if
+ * you must then access data as any data values may be overwritten
+ * by another SCU access by the time this function returns.
+ *
+ * This function may sleep. Locking for SCU accesses is handled for
+ * the caller.
+ */
+int scu_ipc_simple_command(u32 cmd, u32 sub)
+{
+	struct scu *scu;
+	struct udevice *dev;
+	int ret;
+
+	ret = syscon_get_by_driver_data(X86_SYSCON_SCU, &dev);
+	if (ret)
+		return ret;
+
+	scu = dev_get_priv(dev);
+
+	scu_ipc_send_command(scu->regs, sub << 12 | cmd);
+	return scu_ipc_check_status(scu->regs);
+}
+
+int scu_ipc_command(u32 cmd, u32 sub, u32 *in, int inlen, u32 *out, int outlen)
+{
+	struct scu *scu;
+	struct udevice *dev;
+	int ret;
+
+	ret = syscon_get_by_driver_data(X86_SYSCON_SCU, &dev);
+	if (ret)
+		return ret;
+
+	scu = dev_get_priv(dev);
+
+	return scu_ipc_cmd(scu->regs, cmd, sub, in, inlen, out, outlen);
+}
+
+static int scu_ipc_probe(struct udevice *dev)
+{
+	struct scu *scu = dev_get_priv(dev);
+
+	scu->regs = syscon_get_first_range(X86_SYSCON_SCU);
+
+	return 0;
+}
+
+static const struct udevice_id scu_ipc_match[] = {
+	{ .compatible = "intel,scu-ipc", .data = X86_SYSCON_SCU },
+	{ /* sentinel */ }
+};
+
+U_BOOT_DRIVER(scu_ipc) = {
+	.name		= "scu_ipc",
+	.id		= UCLASS_SYSCON,
+	.of_match	= scu_ipc_match,
+	.probe		= scu_ipc_probe,
+	.priv_auto_alloc_size = sizeof(struct scu),
+};