drivers: introduce Secure Monitor uclass

At the moment, we don't have a common API for working with
SM, only the smc_call() function. This approach is not generic
and difficult to configure and maintain.

This patch adds UCLASS_SM with the generic API:

- sm_call()
- sm_call_write()
- sm_call_read()

These functions operate with struct pt_regs, which describes
Secure Monitor arguments.

Signed-off-by: Alexey Romanov <avromanov@salutedevices.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
Link: https://lore.kernel.org/r/20230921081346.22157-2-avromanov@salutedevices.com
Signed-off-by: Neil Armstrong <neil.armstrong@linaro.org>

drivers/Kconfig

@@ -118,6 +118,8 @@ source "drivers/scsi/Kconfig"
 
 source "drivers/serial/Kconfig"
 
+source "drivers/sm/Kconfig"
+
 source "drivers/smem/Kconfig"
 
 source "drivers/sound/Kconfig"

drivers/Makefile

@@ -35,6 +35,7 @@ obj-$(CONFIG_$(SPL_TPL_)VIRTIO) += virtio/
 obj-$(CONFIG_$(SPL_)DM_MAILBOX) += mailbox/
 obj-$(CONFIG_$(SPL_)REMOTEPROC) += remoteproc/
 obj-$(CONFIG_$(SPL_)SYSINFO) += sysinfo/
+obj-$(CONFIG_$(SPL_TPL_)SM) += sm/
 obj-$(CONFIG_$(SPL_TPL_)TPM) += tpm/
 obj-$(CONFIG_$(SPL_)NVME) += nvme/
 obj-$(CONFIG_XEN) += xen/

drivers/sm/Kconfig

@@ -0,0 +1,2 @@
+config SM
+	bool "Enable Secure Monitor driver support"

drivers/sm/Makefile

@@ -0,0 +1,3 @@
+# SPDX-License-Identifier: GPL-2.0-only
+
+obj-y += sm-uclass.o

drivers/sm/sm-uclass.c

@@ -0,0 +1,55 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Copyright (c) 2023 SberDevices, Inc.
+ *
+ * Author: Alexey Romanov <avromanov@salutedevices.com>
+ */
+
+#include <common.h>
+#include <dm.h>
+#include <errno.h>
+#include <sm-uclass.h>
+
+static const struct sm_ops *get_sm_ops(struct udevice *dev)
+{
+	return (const struct sm_ops *)dev->driver->ops;
+}
+
+int sm_call(struct udevice *dev, u32 cmd, s32 *ret, struct pt_regs *args)
+{
+	const struct sm_ops *ops = get_sm_ops(dev);
+
+	if (ops->sm_call)
+		return ops->sm_call(dev, cmd, ret, args);
+
+	return -ENOSYS;
+}
+
+int sm_call_read(struct udevice *dev, void *buffer, size_t size,
+		 u32 cmd, struct pt_regs *args)
+{
+	const struct sm_ops *ops = get_sm_ops(dev);
+
+	if (ops->sm_call_read)
+		return ops->sm_call_read(dev, buffer, size, cmd,
+					 args);
+
+	return -ENOSYS;
+}
+
+int sm_call_write(struct udevice *dev, void *buffer, size_t size,
+		   u32 cmd, struct pt_regs *args)
+{
+	const struct sm_ops *ops = get_sm_ops(dev);
+
+	if (ops->sm_call_write)
+		return ops->sm_call_write(dev, buffer, size, cmd,
+					  args);
+
+	return -ENOSYS;
+}
+
+UCLASS_DRIVER(sm) = {
+	.name           = "sm",
+	.id             = UCLASS_SM,
+};

include/dm/uclass-id.h

@@ -89,6 +89,7 @@ enum uclass_id {
 	UCLASS_MDIO,		/* MDIO bus */
 	UCLASS_MDIO_MUX,	/* MDIO MUX/switch */
 	UCLASS_MEMORY,		/* Memory Controller device */
+	UCLASS_SM,		/* Secure Monitor driver */
 	UCLASS_MISC,		/* Miscellaneous device */
 	UCLASS_MMC,		/* SD / MMC card or chip */
 	UCLASS_MOD_EXP,		/* RSA Mod Exp device */

include/sm-uclass.h

@@ -0,0 +1,72 @@
+/* SPDX-License-Identifier: GPL-2.0+ */
+/*
+ * Copyright (c) 2023 SberDevices, Inc.
+ *
+ * Author: Alexey Romanov <avromanov@salutedevices.com>
+ */
+
+#ifndef __SM_UCLASS_H__
+#define __SM_UCLASS_H__
+
+#include <asm/types.h>
+#include <asm/ptrace.h>
+
+struct udevice;
+
+/**
+ * struct sm_ops - The functions that a SM driver must implement.
+ *
+ * @sm_call: Request a secure monitor call with specified command.
+ *
+ * @sm_call_read: Request a secure monitor call and retrieve data
+ * from secure-monitor (depends on specified command).
+ *
+ * @sm_call_write: Request a secure monitor call and send data
+ * to secure-monitor (depends on specified command).
+ *
+ * The individual methods are described more fully below.
+ */
+struct sm_ops {
+	/**
+	 * sm_call - generic SMC call to the secure-monitor
+	 *
+	 * @dev:	Pointer to UCLASS_SM device
+	 * @cmd_index:	Index of the SMC function ID
+	 * @smc_ret:	Returned value from secure world
+	 * @args:	SMC arguments
+	 *
+	 * @return:	0 on success, a negative value on error
+	 */
+	int (*sm_call)(struct udevice *dev, u32 cmd, s32 *smc_ret,
+		       struct pt_regs *args);
+
+	/**
+	 * sm_call_write - send data to secure-monitor
+	 *
+	 * @dev:	Pointer to UCLASS_SM device
+	 * @buffer:	Buffer containing data to send
+	 * @size:	Size of the buffer
+	 * @cmd:	Index of the SMC function ID
+	 * @args:	SMC arguments
+	 *
+	 * @return:	size of sent data on success, a negative value on error
+	 */
+	int (*sm_call_write)(struct udevice *dev, void *buffer,
+			     size_t size, u32 cmd, struct pt_regs *args);
+
+	/**
+	 * sm_call_read - retrieve data from secure-monitor
+	 *
+	 * @dev:	Pointer to UCLASS_SM device
+	 * @buffer:	Buffer to store the retrieved data
+	 * @size:	Size of the buffer
+	 * @cmd:	Index of the SMC function ID
+	 * @args:	SMC arguments
+	 *
+	 * @return:	size of read data on success, a negative value on error
+	 */
+	int (*sm_call_read)(struct udevice *dev, void *buffer,
+			    size_t size, u32 cmd, struct pt_regs *args);
+};
+
+#endif /* __SM_UCLASS_H__ */

include/sm.h

@@ -0,0 +1,67 @@
+/* SPDX-License-Identifier: GPL-2.0+ */
+/*
+ * Copyright (c) 2023 SberDevices, Inc.
+ *
+ * Author: Alexey Romanov <avromanov@salutedevices.ru>
+ */
+
+#ifndef __SM_H__
+#define __SM_H__
+
+/*
+ * NOTE: UCLASS_SM is designed with the idea that
+ * each driver should convert @cmd to some raw
+ * value, which is known only for driver, and set this
+ * value to the first element of the @args->regs array.
+ * Therefore, it is necessary to pass the remaining
+ * arguments starting at index = 1. Anyway, driver
+ * implementation may vary, so, please, check the specific
+ * implementation of the driver you are using.
+ */
+
+#include <asm/types.h>
+#include <asm/ptrace.h>
+
+struct udevice;
+
+/**
+ * sm_call - generic SMC call to the secure-monitor
+ *
+ * @dev:	Pointer to UCLASS_SM device
+ * @cmd_index:	Index of the SMC function ID
+ * @smc_ret:	Returned value from secure world
+ * @args:	SMC arguments
+ *
+ * @return:	0 on success, a negative value on error
+ */
+int sm_call(struct udevice *dev, u32 cmd, s32 *ret, struct pt_regs *args);
+
+/**
+ * sm_call_read - retrieve data from secure-monitor
+ *
+ * @dev:	Pointer to UCLASS_MESON_SM device
+ * @buffer:	Buffer to store the retrieved data
+ * @size:	Size of the buffer
+ * @cmd:	Index of the SMC function ID
+ * @args:	SMC arguments
+ *
+ * @return:	size of read data on success, a negative value on error
+ */
+int sm_call_read(struct udevice *dev, void *buffer, size_t size,
+		 u32 cmd, struct pt_regs *args);
+
+/**
+ * sm_call_write - send data to secure-monitor
+ *
+ * @dev:	Pointer to UCLASS_SM device
+ * @buffer:	Buffer containing data to send
+ * @size:	Size of the buffer
+ * @cmd:	Index of the SMC function ID
+ * @args:	SMC arguments
+ *
+ * @return:	size of sent data on success, a negative value on error
+ */
+int sm_call_write(struct udevice *dev, void *buffer, size_t size,
+		  u32 cmd, struct pt_regs *args);
+
+#endif /* __SM_H__ */