/*
   * Copyright (C) 2001-2006 Silicon Graphics, Inc.  All rights
   * reserved.
   *
   * This program is free software; you can redistribute it and/or modify it
   * under the terms of version 2 of the GNU General Public License
   * as published by the Free Software Foundation.
   */
  
  /*
   * SN Platform Special Memory (mspec) Support
   *
   * This driver exports the SN special memory (mspec) facility to user
   * processes.
   * There are three types of memory made available thru this driver:
   * fetchops, uncached and cached.
   *
   * Fetchops are atomic memory operations that are implemented in the
   * memory controller on SGI SN hardware.
   *
   * Uncached are used for memory write combining feature of the ia64
   * cpu.
   *
   * Cached are used for areas of memory that are used as cached addresses
   * on our partition and used as uncached addresses from other partitions.
   * Due to a design constraint of the SN2 Shub, you can not have processors
   * on the same FSB perform both a cached and uncached reference to the
   * same cache line.  These special memory cached regions prevent the
   * kernel from ever dropping in a TLB entry and therefore prevent the
   * processor from ever speculating a cache line from this page.
   */
  
  #include <linux/types.h>
  #include <linux/kernel.h>
  #include <linux/module.h>
  #include <linux/init.h>
  #include <linux/errno.h>
  #include <linux/miscdevice.h>
  #include <linux/spinlock.h>
  #include <linux/mm.h>
  #include <linux/fs.h>
  #include <linux/vmalloc.h>
  #include <linux/string.h>
  #include <linux/slab.h>
  #include <linux/numa.h>
  #include <asm/page.h>
  #include <asm/pgtable.h>
  #include <linux/atomic.h>
  #include <asm/tlbflush.h>
  #include <asm/uncached.h>
  #include <asm/sn/addrs.h>
  #include <asm/sn/arch.h>
  #include <asm/sn/mspec.h>
  #include <asm/sn/sn_cpuid.h>
  #include <asm/sn/io.h>
  #include <asm/sn/bte.h>
  #include <asm/sn/shubio.h>
  
  
  #define FETCHOP_ID	"SGI Fetchop,"
  #define CACHED_ID	"Cached,"
  #define UNCACHED_ID	"Uncached"
  #define REVISION	"4.0"
  #define MSPEC_BASENAME	"mspec"
  
  /*
   * Page types allocated by the device.
   */
  enum mspec_page_type {
  	MSPEC_FETCHOP = 1,
  	MSPEC_CACHED,
  	MSPEC_UNCACHED
  };
  
  #ifdef CONFIG_SGI_SN
  static int is_sn2;
  #else
  #define is_sn2		0
  #endif
  
  /*
   * One of these structures is allocated when an mspec region is mmaped. The
   * structure is pointed to by the vma->vm_private_data field in the vma struct.
   * This structure is used to record the addresses of the mspec pages.
   * This structure is shared by all vma's that are split off from the
   * original vma when split_vma()'s are done.
   *
   * The refcnt is incremented atomically because mm->mmap_sem does not
   * protect in fork case where multiple tasks share the vma_data.
   */
  struct vma_data {
  	atomic_t refcnt;	/* Number of vmas sharing the data. */
  	spinlock_t lock;	/* Serialize access to this structure. */
  	int count;		/* Number of pages allocated. */
  	enum mspec_page_type type; /* Type of pages allocated. */
  	int flags;		/* See VMD_xxx below. */
  	unsigned long vm_start;	/* Original (unsplit) base. */
  	unsigned long vm_end;	/* Original (unsplit) end. */
  	unsigned long maddr[0];	/* Array of MSPEC addresses. */
  };
  
  #define VMD_VMALLOCED 0x1	/* vmalloc'd rather than kmalloc'd */
  
  /* used on shub2 to clear FOP cache in the HUB */
  static unsigned long scratch_page[MAX_NUMNODES];
  #define SH2_AMO_CACHE_ENTRIES	4
  
  static inline int
  mspec_zero_block(unsigned long addr, int len)
  {
  	int status;
  
  	if (is_sn2) {
  		if (is_shub2()) {
  			int nid;
  			void *p;
  			int i;
  
  			nid = nasid_to_cnodeid(get_node_number(__pa(addr)));
  			p = (void *)TO_AMO(scratch_page[nid]);
  
  			for (i=0; i < SH2_AMO_CACHE_ENTRIES; i++) {
  				FETCHOP_LOAD_OP(p, FETCHOP_LOAD);
  				p += FETCHOP_VAR_SIZE;
  			}
  		}
  
  		status = bte_copy(0, addr & ~__IA64_UNCACHED_OFFSET, len,
  				  BTE_WACQUIRE | BTE_ZERO_FILL, NULL);
  	} else {
  		memset((char *) addr, 0, len);
  		status = 0;
  	}
  	return status;
  }
  
  /*
   * mspec_open
   *
   * Called when a device mapping is created by a means other than mmap
   * (via fork, munmap, etc.).  Increments the reference count on the
   * underlying mspec data so it is not freed prematurely.
   */
  static void
  mspec_open(struct vm_area_struct *vma)
  {
  	struct vma_data *vdata;
  
  	vdata = vma->vm_private_data;
  	atomic_inc(&vdata->refcnt);
  }
  
  /*
   * mspec_close
   *
   * Called when unmapping a device mapping. Frees all mspec pages
   * belonging to all the vma's sharing this vma_data structure.
   */
  static void
  mspec_close(struct vm_area_struct *vma)
  {
  	struct vma_data *vdata;
  	int index, last_index;
  	unsigned long my_page;
  
  	vdata = vma->vm_private_data;
  
  	if (!atomic_dec_and_test(&vdata->refcnt))
  		return;
  
  	last_index = (vdata->vm_end - vdata->vm_start) >> PAGE_SHIFT;
  	for (index = 0; index < last_index; index++) {
  		if (vdata->maddr[index] == 0)
  			continue;
  		/*
  		 * Clear the page before sticking it back
  		 * into the pool.
  		 */
  		my_page = vdata->maddr[index];
  		vdata->maddr[index] = 0;
  		if (!mspec_zero_block(my_page, PAGE_SIZE))
  			uncached_free_page(my_page, 1);
  		else
  			printk(KERN_WARNING "mspec_close(): "
  			       "failed to zero page %ld
  ", my_page);
  	}
  
  	if (vdata->flags & VMD_VMALLOCED)
  		vfree(vdata);
  	else
  		kfree(vdata);
  }
  
  /*
   * mspec_fault
   *
   * Creates a mspec page and maps it to user space.
   */
  static int
  mspec_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
  {
  	unsigned long paddr, maddr;
  	unsigned long pfn;
  	pgoff_t index = vmf->pgoff;
  	struct vma_data *vdata = vma->vm_private_data;
  
  	maddr = (volatile unsigned long) vdata->maddr[index];
  	if (maddr == 0) {
  		maddr = uncached_alloc_page(numa_node_id(), 1);
  		if (maddr == 0)
  			return VM_FAULT_OOM;
  
  		spin_lock(&vdata->lock);
  		if (vdata->maddr[index] == 0) {
  			vdata->count++;
  			vdata->maddr[index] = maddr;
  		} else {
  			uncached_free_page(maddr, 1);
  			maddr = vdata->maddr[index];
  		}
  		spin_unlock(&vdata->lock);
  	}
  
  	if (vdata->type == MSPEC_FETCHOP)
  		paddr = TO_AMO(maddr);
  	else
  		paddr = maddr & ~__IA64_UNCACHED_OFFSET;
  
  	pfn = paddr >> PAGE_SHIFT;
  
  	/*
  	 * vm_insert_pfn can fail with -EBUSY, but in that case it will
  	 * be because another thread has installed the pte first, so it
  	 * is no problem.
  	 */
  	vm_insert_pfn(vma, (unsigned long)vmf->virtual_address, pfn);
  
  	return VM_FAULT_NOPAGE;
  }
  
  static const struct vm_operations_struct mspec_vm_ops = {
  	.open = mspec_open,
  	.close = mspec_close,
  	.fault = mspec_fault,
  };
  
  /*
   * mspec_mmap
   *
   * Called when mmapping the device.  Initializes the vma with a fault handler
   * and private data structure necessary to allocate, track, and free the
   * underlying pages.
   */
  static int
  mspec_mmap(struct file *file, struct vm_area_struct *vma,
  					enum mspec_page_type type)
  {
  	struct vma_data *vdata;
  	int pages, vdata_size, flags = 0;
  
  	if (vma->vm_pgoff != 0)
  		return -EINVAL;
  
  	if ((vma->vm_flags & VM_SHARED) == 0)
  		return -EINVAL;
  
  	if ((vma->vm_flags & VM_WRITE) == 0)
  		return -EPERM;
  
  	pages = vma_pages(vma);
  	vdata_size = sizeof(struct vma_data) + pages * sizeof(long);
  	if (vdata_size <= PAGE_SIZE)
  		vdata = kzalloc(vdata_size, GFP_KERNEL);
  	else {
  		vdata = vzalloc(vdata_size);
  		flags = VMD_VMALLOCED;
  	}
  	if (!vdata)
  		return -ENOMEM;
  
  	vdata->vm_start = vma->vm_start;
  	vdata->vm_end = vma->vm_end;
  	vdata->flags = flags;
  	vdata->type = type;
  	spin_lock_init(&vdata->lock);
  	atomic_set(&vdata->refcnt, 1);
  	vma->vm_private_data = vdata;
  
  	vma->vm_flags |= VM_IO | VM_PFNMAP | VM_DONTEXPAND | VM_DONTDUMP;
  	if (vdata->type == MSPEC_FETCHOP || vdata->type == MSPEC_UNCACHED)
  		vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);
  	vma->vm_ops = &mspec_vm_ops;
  
  	return 0;
  }
  
  static int
  fetchop_mmap(struct file *file, struct vm_area_struct *vma)
  {
  	return mspec_mmap(file, vma, MSPEC_FETCHOP);
  }
  
  static int
  cached_mmap(struct file *file, struct vm_area_struct *vma)
  {
  	return mspec_mmap(file, vma, MSPEC_CACHED);
  }
  
  static int
  uncached_mmap(struct file *file, struct vm_area_struct *vma)
  {
  	return mspec_mmap(file, vma, MSPEC_UNCACHED);
  }
  
  static const struct file_operations fetchop_fops = {
  	.owner = THIS_MODULE,
  	.mmap = fetchop_mmap,
  	.llseek = noop_llseek,
  };
  
  static struct miscdevice fetchop_miscdev = {
  	.minor = MISC_DYNAMIC_MINOR,
  	.name = "sgi_fetchop",
  	.fops = &fetchop_fops
  };
  
  static const struct file_operations cached_fops = {
  	.owner = THIS_MODULE,
  	.mmap = cached_mmap,
  	.llseek = noop_llseek,
  };
  
  static struct miscdevice cached_miscdev = {
  	.minor = MISC_DYNAMIC_MINOR,
  	.name = "mspec_cached",
  	.fops = &cached_fops
  };
  
  static const struct file_operations uncached_fops = {
  	.owner = THIS_MODULE,
  	.mmap = uncached_mmap,
  	.llseek = noop_llseek,
  };
  
  static struct miscdevice uncached_miscdev = {
  	.minor = MISC_DYNAMIC_MINOR,
  	.name = "mspec_uncached",
  	.fops = &uncached_fops
  };
  
  /*
   * mspec_init
   *
   * Called at boot time to initialize the mspec facility.
   */
  static int __init
  mspec_init(void)
  {
  	int ret;
  	int nid;
  
  	/*
  	 * The fetchop device only works on SN2 hardware, uncached and cached
  	 * memory drivers should both be valid on all ia64 hardware
  	 */
  #ifdef CONFIG_SGI_SN
  	if (ia64_platform_is("sn2")) {
  		is_sn2 = 1;
  		if (is_shub2()) {
  			ret = -ENOMEM;
  			for_each_node_state(nid, N_ONLINE) {
  				int actual_nid;
  				int nasid;
  				unsigned long phys;
  
  				scratch_page[nid] = uncached_alloc_page(nid, 1);
  				if (scratch_page[nid] == 0)
  					goto free_scratch_pages;
  				phys = __pa(scratch_page[nid]);
  				nasid = get_node_number(phys);
  				actual_nid = nasid_to_cnodeid(nasid);
  				if (actual_nid != nid)
  					goto free_scratch_pages;
  			}
  		}
  
  		ret = misc_register(&fetchop_miscdev);
  		if (ret) {
  			printk(KERN_ERR
  			       "%s: failed to register device %i
  ",
  			       FETCHOP_ID, ret);
  			goto free_scratch_pages;
  		}
  	}
  #endif
  	ret = misc_register(&cached_miscdev);
  	if (ret) {
  		printk(KERN_ERR "%s: failed to register device %i
  ",
  		       CACHED_ID, ret);
  		if (is_sn2)
  			misc_deregister(&fetchop_miscdev);
  		goto free_scratch_pages;
  	}
  	ret = misc_register(&uncached_miscdev);
  	if (ret) {
  		printk(KERN_ERR "%s: failed to register device %i
  ",
  		       UNCACHED_ID, ret);
  		misc_deregister(&cached_miscdev);
  		if (is_sn2)
  			misc_deregister(&fetchop_miscdev);
  		goto free_scratch_pages;
  	}
  
  	printk(KERN_INFO "%s %s initialized devices: %s %s %s
  ",
  	       MSPEC_BASENAME, REVISION, is_sn2 ? FETCHOP_ID : "",
  	       CACHED_ID, UNCACHED_ID);
  
  	return 0;
  
   free_scratch_pages:
  	for_each_node(nid) {
  		if (scratch_page[nid] != 0)
  			uncached_free_page(scratch_page[nid], 1);
  	}
  	return ret;
  }
  
  static void __exit
  mspec_exit(void)
  {
  	int nid;
  
  	misc_deregister(&uncached_miscdev);
  	misc_deregister(&cached_miscdev);
  	if (is_sn2) {
  		misc_deregister(&fetchop_miscdev);
  
  		for_each_node(nid) {
  			if (scratch_page[nid] != 0)
  				uncached_free_page(scratch_page[nid], 1);
  		}
  	}
  }
  
  module_init(mspec_init);
  module_exit(mspec_exit);
  
  MODULE_AUTHOR("Silicon Graphics, Inc. <linux-altix@sgi.com>");
  MODULE_DESCRIPTION("Driver for SGI SN special memory operations");
  MODULE_LICENSE("GPL");