msm: Secure Channel Manager (SCM) support

SCM is the protocol used to communicate between the secure and
non-secure code executing on the applications processor. The
non-secure side uses a physically contiguous buffer to pass
information to the secure side; where the buffer conforms to a
format that is agreed upon by both sides. The use of a buffer
allows multiple pending requests to be in flight on the secure
side. It also benefits use cases where the command or response
buffer contains large chunks of data.

Reviewed-by: Saravana Kannan <skannan@codeaurora.org>
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>
Signed-off-by: David Brown <davidb@codeaurora.org>

1 files changed, 287 insertions, 0 deletions

diff --git a/arch/arm/mach-msm/scm.c b/arch/arm/mach-msm/scm.c
new file mode 100644
index 0000000..f4b9bc9
--- /dev/null
+++ b/arch/arm/mach-msm/scm.c
@@ -0,0 +1,287 @@
+/* Copyright (c) 2010, Code Aurora Forum. All rights reserved.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 and
+ * only version 2 as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
+ * 02110-1301, USA.
+ */
+
+#include <linux/slab.h>
+#include <linux/io.h>
+#include <linux/module.h>
+#include <linux/mutex.h>
+#include <linux/errno.h>
+#include <linux/err.h>
+
+#include <asm/cacheflush.h>
+
+#include "scm.h"
+
+/* Cache line size for msm8x60 */
+#define CACHELINESIZE 32
+
+#define SCM_ENOMEM		-5
+#define SCM_EOPNOTSUPP		-4
+#define SCM_EINVAL_ADDR		-3
+#define SCM_EINVAL_ARG		-2
+#define SCM_ERROR		-1
+#define SCM_INTERRUPTED		1
+
+static DEFINE_MUTEX(scm_lock);
+
+/**
+ * struct scm_command - one SCM command buffer
+ * @len: total available memory for command and response
+ * @buf_offset: start of command buffer
+ * @resp_hdr_offset: start of response buffer
+ * @id: command to be executed
+ * @buf: buffer returned from scm_get_command_buffer()
+ *
+ * An SCM command is layed out in memory as follows:
+ *
+ *	------------------- <--- struct scm_command
+ *	| command header  |
+ *	------------------- <--- scm_get_command_buffer()
+ *	| command buffer  |
+ *	------------------- <--- struct scm_response and
+ *	| response header |      scm_command_to_response()
+ *	------------------- <--- scm_get_response_buffer()
+ *	| response buffer |
+ *	-------------------
+ *
+ * There can be arbitrary padding between the headers and buffers so
+ * you should always use the appropriate scm_get_*_buffer() routines
+ * to access the buffers in a safe manner.
+ */
+struct scm_command {
+	u32	len;
+	u32	buf_offset;
+	u32	resp_hdr_offset;
+	u32	id;
+	u32	buf[0];
+};
+
+/**
+ * struct scm_response - one SCM response buffer
+ * @len: total available memory for response
+ * @buf_offset: start of response data relative to start of scm_response
+ * @is_complete: indicates if the command has finished processing
+ */
+struct scm_response {
+	u32	len;
+	u32	buf_offset;
+	u32	is_complete;
+};
+
+/**
+ * alloc_scm_command() - Allocate an SCM command
+ * @cmd_size: size of the command buffer
+ * @resp_size: size of the response buffer
+ *
+ * Allocate an SCM command, including enough room for the command
+ * and response headers as well as the command and response buffers.
+ *
+ * Returns a valid &scm_command on success or %NULL if the allocation fails.
+ */
+static struct scm_command *alloc_scm_command(size_t cmd_size, size_t resp_size)
+{
+	struct scm_command *cmd;
+	size_t len = sizeof(*cmd) + sizeof(struct scm_response) + cmd_size +
+		resp_size;
+
+	cmd = kzalloc(PAGE_ALIGN(len), GFP_KERNEL);
+	if (cmd) {
+		cmd->len = len;
+		cmd->buf_offset = offsetof(struct scm_command, buf);
+		cmd->resp_hdr_offset = cmd->buf_offset + cmd_size;
+	}
+	return cmd;
+}
+
+/**
+ * free_scm_command() - Free an SCM command
+ * @cmd: command to free
+ *
+ * Free an SCM command.
+ */
+static inline void free_scm_command(struct scm_command *cmd)
+{
+	kfree(cmd);
+}
+
+/**
+ * scm_command_to_response() - Get a pointer to a scm_response
+ * @cmd: command
+ *
+ * Returns a pointer to a response for a command.
+ */
+static inline struct scm_response *scm_command_to_response(
+		const struct scm_command *cmd)
+{
+	return (void *)cmd + cmd->resp_hdr_offset;
+}
+
+/**
+ * scm_get_command_buffer() - Get a pointer to a command buffer
+ * @cmd: command
+ *
+ * Returns a pointer to the command buffer of a command.
+ */
+static inline void *scm_get_command_buffer(const struct scm_command *cmd)
+{
+	return (void *)cmd->buf;
+}
+
+/**
+ * scm_get_response_buffer() - Get a pointer to a response buffer
+ * @rsp: response
+ *
+ * Returns a pointer to a response buffer of a response.
+ */
+static inline void *scm_get_response_buffer(const struct scm_response *rsp)
+{
+	return (void *)rsp + rsp->buf_offset;
+}
+
+static int scm_remap_error(int err)
+{
+	switch (err) {
+	case SCM_ERROR:
+		return -EIO;
+	case SCM_EINVAL_ADDR:
+	case SCM_EINVAL_ARG:
+		return -EINVAL;
+	case SCM_EOPNOTSUPP:
+		return -EOPNOTSUPP;
+	case SCM_ENOMEM:
+		return -ENOMEM;
+	}
+	return -EINVAL;
+}
+
+static u32 smc(u32 cmd_addr)
+{
+	int context_id;
+	register u32 r0 asm("r0") = 1;
+	register u32 r1 asm("r1") = (u32)&context_id;
+	register u32 r2 asm("r2") = cmd_addr;
+	asm(
+		__asmeq("%0", "r0")
+		__asmeq("%1", "r0")
+		__asmeq("%2", "r1")
+		__asmeq("%3", "r2")
+		"smc	#0	@ switch to secure world\n"
+		: "=r" (r0)
+		: "r" (r0), "r" (r1), "r" (r2)
+		: "r3");
+	return r0;
+}
+
+static int __scm_call(const struct scm_command *cmd)
+{
+	int ret;
+	u32 cmd_addr = virt_to_phys(cmd);
+
+	/*
+	 * Flush the entire cache here so callers don't have to remember
+	 * to flush the cache when passing physical addresses to the secure
+	 * side in the buffer.
+	 */
+	flush_cache_all();
+	do {
+		ret = smc(cmd_addr);
+		if (ret < 0) {
+			ret = scm_remap_error(ret);
+			break;
+		}
+	} while (ret == SCM_INTERRUPTED);
+
+	return ret;
+}
+
+/**
+ * scm_call() - Send an SCM command
+ * @svc_id: service identifier
+ * @cmd_id: command identifier
+ * @cmd_buf: command buffer
+ * @cmd_len: length of the command buffer
+ * @resp_buf: response buffer
+ * @resp_len: length of the response buffer
+ *
+ * Sends a command to the SCM and waits for the command to finish processing.
+ */
+int scm_call(u32 svc_id, u32 cmd_id, const void *cmd_buf, size_t cmd_len,
+		void *resp_buf, size_t resp_len)
+{
+	int ret;
+	struct scm_command *cmd;
+	struct scm_response *rsp;
+
+	cmd = alloc_scm_command(cmd_len, resp_len);
+	if (!cmd)
+		return -ENOMEM;
+
+	cmd->id = (svc_id << 10) | cmd_id;
+	if (cmd_buf)
+		memcpy(scm_get_command_buffer(cmd), cmd_buf, cmd_len);
+
+	mutex_lock(&scm_lock);
+	ret = __scm_call(cmd);
+	mutex_unlock(&scm_lock);
+	if (ret)
+		goto out;
+
+	rsp = scm_command_to_response(cmd);
+	do {
+		u32 start = (u32)rsp;
+		u32 end = (u32)scm_get_response_buffer(rsp) + resp_len;
+		start &= ~(CACHELINESIZE - 1);
+		while (start < end) {
+			asm ("mcr p15, 0, %0, c7, c6, 1" : : "r" (start)
+			     : "memory");
+			start += CACHELINESIZE;
+		}
+	} while (!rsp->is_complete);
+
+	if (resp_buf)
+		memcpy(resp_buf, scm_get_response_buffer(rsp), resp_len);
+out:
+	free_scm_command(cmd);
+	return ret;
+}
+EXPORT_SYMBOL(scm_call);
+
+u32 scm_get_version(void)
+{
+	int context_id;
+	static u32 version = -1;
+	register u32 r0 asm("r0") = 0x1 << 8;
+	register u32 r1 asm("r1") = (u32)&context_id;
+
+	if (version != -1)
+		return version;
+
+	mutex_lock(&scm_lock);
+	asm(
+		__asmeq("%0", "r1")
+		__asmeq("%1", "r0")
+		__asmeq("%2", "r1")
+		"smc	#0	@ switch to secure world\n"
+		: "=r" (r1)
+		: "r" (r0), "r" (r1)
+		: "r2", "r3");
+	version = r1;
+	mutex_unlock(&scm_lock);
+
+	return version;
+}
+EXPORT_SYMBOL(scm_get_version);