/* 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 laid 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;
  	do {
  		asm volatile(
  			__asmeq("%0", "r0")
  			__asmeq("%1", "r0")
  			__asmeq("%2", "r1")
  			__asmeq("%3", "r2")
  #ifdef REQUIRES_SEC
  			".arch_extension sec
  "
  #endif
  			"smc	#0	@ switch to secure world
  "
  			: "=r" (r0)
  			: "r" (r0), "r" (r1), "r" (r2)
  			: "r3");
  	} while (r0 == SCM_INTERRUPTED);
  
  	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();
  	ret = smc(cmd_addr);
  	if (ret < 0)
  		ret = scm_remap_error(ret);
  
  	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");
  	register u32 r1 asm("r1");
  
  	if (version != -1)
  		return version;
  
  	mutex_lock(&scm_lock);
  
  	r0 = 0x1 << 8;
  	r1 = (u32)&context_id;
  	do {
  		asm volatile(
  			__asmeq("%0", "r0")
  			__asmeq("%1", "r1")
  			__asmeq("%2", "r0")
  			__asmeq("%3", "r1")
  #ifdef REQUIRES_SEC
  			".arch_extension sec
  "
  #endif
  			"smc	#0	@ switch to secure world
  "
  			: "=r" (r0), "=r" (r1)
  			: "r" (r0), "r" (r1)
  			: "r2", "r3");
  	} while (r0 == SCM_INTERRUPTED);
  
  	version = r1;
  	mutex_unlock(&scm_lock);
  
  	return version;
  }
  EXPORT_SYMBOL(scm_get_version);