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iommu.c

/*
 * IOMMU implementation for Cell Broadband Processor Architecture
 *
 * (C) Copyright IBM Corporation 2006
 *
 * Author: Jeremy Kerr <jk@ozlabs.org>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2, or (at your option)
 * any later version.
 *
 * 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., 675 Mass Ave, Cambridge, MA 02139, USA.
 */

#undef DEBUG

#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/interrupt.h>
#include <linux/notifier.h>

#include <asm/prom.h>
#include <asm/iommu.h>
#include <asm/machdep.h>
#include <asm/pci-bridge.h>
#include <asm/udbg.h>
#include <asm/of_platform.h>
#include <asm/lmb.h>
#include <asm/cell-regs.h>

#include "interrupt.h"

/* Define CELL_IOMMU_REAL_UNMAP to actually unmap non-used pages
 * instead of leaving them mapped to some dummy page. This can be
 * enabled once the appropriate workarounds for spider bugs have
 * been enabled
 */
#define CELL_IOMMU_REAL_UNMAP

/* Define CELL_IOMMU_STRICT_PROTECTION to enforce protection of
 * IO PTEs based on the transfer direction. That can be enabled
 * once spider-net has been fixed to pass the correct direction
 * to the DMA mapping functions
 */
#define CELL_IOMMU_STRICT_PROTECTION


#define NR_IOMMUS             2

/* IOC mmap registers */
#define IOC_Reg_Size                0x2000

#define IOC_IOPT_CacheInvd          0x908
#define IOC_IOPT_CacheInvd_NE_Mask  0xffe0000000000000ul
#define IOC_IOPT_CacheInvd_IOPTE_Mask     0x000003fffffffff8ul
#define IOC_IOPT_CacheInvd_Busy           0x0000000000000001ul

#define IOC_IOST_Origin             0x918
#define IOC_IOST_Origin_E           0x8000000000000000ul
#define IOC_IOST_Origin_HW          0x0000000000000800ul
#define IOC_IOST_Origin_HL          0x0000000000000400ul

#define IOC_IO_ExcpStat             0x920
#define IOC_IO_ExcpStat_V           0x8000000000000000ul
#define IOC_IO_ExcpStat_SPF_Mask    0x6000000000000000ul
#define IOC_IO_ExcpStat_SPF_S       0x6000000000000000ul
#define IOC_IO_ExcpStat_SPF_P       0x4000000000000000ul
#define IOC_IO_ExcpStat_ADDR_Mask   0x00000007fffff000ul
#define IOC_IO_ExcpStat_RW_Mask           0x0000000000000800ul
#define IOC_IO_ExcpStat_IOID_Mask   0x00000000000007fful

#define IOC_IO_ExcpMask             0x928
#define IOC_IO_ExcpMask_SFE         0x4000000000000000ul
#define IOC_IO_ExcpMask_PFE         0x2000000000000000ul

#define IOC_IOCmd_Offset            0x1000

#define IOC_IOCmd_Cfg               0xc00
#define IOC_IOCmd_Cfg_TE            0x0000800000000000ul


/* Segment table entries */
#define IOSTE_V               0x8000000000000000ul /* valid */
#define IOSTE_H               0x4000000000000000ul /* cache hint */
#define IOSTE_PT_Base_RPN_Mask  0x3ffffffffffff000ul /* base RPN of IOPT */
#define IOSTE_NPPT_Mask       0x0000000000000fe0ul /* no. pages in IOPT */
#define IOSTE_PS_Mask         0x0000000000000007ul /* page size */
#define IOSTE_PS_4K           0x0000000000000001ul /*   - 4kB  */
#define IOSTE_PS_64K          0x0000000000000003ul /*   - 64kB */
#define IOSTE_PS_1M           0x0000000000000005ul /*   - 1MB  */
#define IOSTE_PS_16M          0x0000000000000007ul /*   - 16MB */

/* Page table entries */
#define IOPTE_PP_W            0x8000000000000000ul /* protection: write */
#define IOPTE_PP_R            0x4000000000000000ul /* protection: read */
#define IOPTE_M               0x2000000000000000ul /* coherency required */
#define IOPTE_SO_R            0x1000000000000000ul /* ordering: writes */
#define IOPTE_SO_RW             0x1800000000000000ul /* ordering: r & w */
#define IOPTE_RPN_Mask        0x07fffffffffff000ul /* RPN */
#define IOPTE_H               0x0000000000000800ul /* cache hint */
#define IOPTE_IOID_Mask       0x00000000000007fful /* ioid */


/* IOMMU sizing */
#define IO_SEGMENT_SHIFT      28
#define IO_PAGENO_BITS        (IO_SEGMENT_SHIFT - IOMMU_PAGE_SHIFT)

/* The high bit needs to be set on every DMA address */
#define SPIDER_DMA_OFFSET     0x80000000ul

struct iommu_window {
      struct list_head list;
      struct cbe_iommu *iommu;
      unsigned long offset;
      unsigned long size;
      unsigned long pte_offset;
      unsigned int ioid;
      struct iommu_table table;
};

#define NAMESIZE 8
struct cbe_iommu {
      int nid;
      char name[NAMESIZE];
      void __iomem *xlate_regs;
      void __iomem *cmd_regs;
      unsigned long *stab;
      unsigned long *ptab;
      void *pad_page;
      struct list_head windows;
};

/* Static array of iommus, one per node
 *   each contains a list of windows, keyed from dma_window property
 *   - on bus setup, look for a matching window, or create one
 *   - on dev setup, assign iommu_table ptr
 */
static struct cbe_iommu iommus[NR_IOMMUS];
static int cbe_nr_iommus;

static void invalidate_tce_cache(struct cbe_iommu *iommu, unsigned long *pte,
            long n_ptes)
{
      unsigned long __iomem *reg;
      unsigned long val;
      long n;

      reg = iommu->xlate_regs + IOC_IOPT_CacheInvd;

      while (n_ptes > 0) {
            /* we can invalidate up to 1 << 11 PTEs at once */
            n = min(n_ptes, 1l << 11);
            val = (((n /*- 1*/) << 53) & IOC_IOPT_CacheInvd_NE_Mask)
                  | (__pa(pte) & IOC_IOPT_CacheInvd_IOPTE_Mask)
                    | IOC_IOPT_CacheInvd_Busy;

            out_be64(reg, val);
            while (in_be64(reg) & IOC_IOPT_CacheInvd_Busy)
                  ;

            n_ptes -= n;
            pte += n;
      }
}

static void tce_build_cell(struct iommu_table *tbl, long index, long npages,
            unsigned long uaddr, enum dma_data_direction direction)
{
      int i;
      unsigned long *io_pte, base_pte;
      struct iommu_window *window =
            container_of(tbl, struct iommu_window, table);

      /* implementing proper protection causes problems with the spidernet
       * driver - check mapping directions later, but allow read & write by
       * default for now.*/
#ifdef CELL_IOMMU_STRICT_PROTECTION
      /* to avoid referencing a global, we use a trick here to setup the
       * protection bit. "prot" is setup to be 3 fields of 4 bits apprended
       * together for each of the 3 supported direction values. It is then
       * shifted left so that the fields matching the desired direction
       * lands on the appropriate bits, and other bits are masked out.
       */
      const unsigned long prot = 0xc48;
      base_pte =
            ((prot << (52 + 4 * direction)) & (IOPTE_PP_W | IOPTE_PP_R))
            | IOPTE_M | IOPTE_SO_RW | (window->ioid & IOPTE_IOID_Mask);
#else
      base_pte = IOPTE_PP_W | IOPTE_PP_R | IOPTE_M | IOPTE_SO_RW |
            (window->ioid & IOPTE_IOID_Mask);
#endif

      io_pte = (unsigned long *)tbl->it_base + (index - window->pte_offset);

      for (i = 0; i < npages; i++, uaddr += IOMMU_PAGE_SIZE)
            io_pte[i] = base_pte | (__pa(uaddr) & IOPTE_RPN_Mask);

      mb();

      invalidate_tce_cache(window->iommu, io_pte, npages);

      pr_debug("tce_build_cell(index=%lx,n=%lx,dir=%d,base_pte=%lx)\n",
             index, npages, direction, base_pte);
}

static void tce_free_cell(struct iommu_table *tbl, long index, long npages)
{

      int i;
      unsigned long *io_pte, pte;
      struct iommu_window *window =
            container_of(tbl, struct iommu_window, table);

      pr_debug("tce_free_cell(index=%lx,n=%lx)\n", index, npages);

#ifdef CELL_IOMMU_REAL_UNMAP
      pte = 0;
#else
      /* spider bridge does PCI reads after freeing - insert a mapping
       * to a scratch page instead of an invalid entry */
      pte = IOPTE_PP_R | IOPTE_M | IOPTE_SO_RW | __pa(window->iommu->pad_page)
            | (window->ioid & IOPTE_IOID_Mask);
#endif

      io_pte = (unsigned long *)tbl->it_base + (index - window->pte_offset);

      for (i = 0; i < npages; i++)
            io_pte[i] = pte;

      mb();

      invalidate_tce_cache(window->iommu, io_pte, npages);
}

static irqreturn_t ioc_interrupt(int irq, void *data)
{
      unsigned long stat;
      struct cbe_iommu *iommu = data;

      stat = in_be64(iommu->xlate_regs + IOC_IO_ExcpStat);

      /* Might want to rate limit it */
      printk(KERN_ERR "iommu: DMA exception 0x%016lx\n", stat);
      printk(KERN_ERR "  V=%d, SPF=[%c%c], RW=%s, IOID=0x%04x\n",
             !!(stat & IOC_IO_ExcpStat_V),
             (stat & IOC_IO_ExcpStat_SPF_S) ? 'S' : ' ',
             (stat & IOC_IO_ExcpStat_SPF_P) ? 'P' : ' ',
             (stat & IOC_IO_ExcpStat_RW_Mask) ? "Read" : "Write",
             (unsigned int)(stat & IOC_IO_ExcpStat_IOID_Mask));
      printk(KERN_ERR "  page=0x%016lx\n",
             stat & IOC_IO_ExcpStat_ADDR_Mask);

      /* clear interrupt */
      stat &= ~IOC_IO_ExcpStat_V;
      out_be64(iommu->xlate_regs + IOC_IO_ExcpStat, stat);

      return IRQ_HANDLED;
}

static int cell_iommu_find_ioc(int nid, unsigned long *base)
{
      struct device_node *np;
      struct resource r;

      *base = 0;

      /* First look for new style /be nodes */
      for_each_node_by_name(np, "ioc") {
            if (of_node_to_nid(np) != nid)
                  continue;
            if (of_address_to_resource(np, 0, &r)) {
                  printk(KERN_ERR "iommu: can't get address for %s\n",
                         np->full_name);
                  continue;
            }
            *base = r.start;
            of_node_put(np);
            return 0;
      }

      /* Ok, let's try the old way */
      for_each_node_by_type(np, "cpu") {
            const unsigned int *nidp;
            const unsigned long *tmp;

            nidp = of_get_property(np, "node-id", NULL);
            if (nidp && *nidp == nid) {
                  tmp = of_get_property(np, "ioc-translation", NULL);
                  if (tmp) {
                        *base = *tmp;
                        of_node_put(np);
                        return 0;
                  }
            }
      }

      return -ENODEV;
}

static void cell_iommu_setup_hardware(struct cbe_iommu *iommu, unsigned long size)
{
      struct page *page;
      int ret, i;
      unsigned long reg, segments, pages_per_segment, ptab_size, n_pte_pages;
      unsigned long xlate_base;
      unsigned int virq;

      if (cell_iommu_find_ioc(iommu->nid, &xlate_base))
            panic("%s: missing IOC register mappings for node %d\n",
                  __FUNCTION__, iommu->nid);

      iommu->xlate_regs = ioremap(xlate_base, IOC_Reg_Size);
      iommu->cmd_regs = iommu->xlate_regs + IOC_IOCmd_Offset;

      segments = size >> IO_SEGMENT_SHIFT;
      pages_per_segment = 1ull << IO_PAGENO_BITS;

      pr_debug("%s: iommu[%d]: segments: %lu, pages per segment: %lu\n",
                  __FUNCTION__, iommu->nid, segments, pages_per_segment);

      /* set up the segment table */
      page = alloc_pages_node(iommu->nid, GFP_KERNEL, 0);
      BUG_ON(!page);
      iommu->stab = page_address(page);
      clear_page(iommu->stab);

      /* ... and the page tables. Since these are contiguous, we can treat
       * the page tables as one array of ptes, like pSeries does.
       */
      ptab_size = segments * pages_per_segment * sizeof(unsigned long);
      pr_debug("%s: iommu[%d]: ptab_size: %lu, order: %d\n", __FUNCTION__,
                  iommu->nid, ptab_size, get_order(ptab_size));
      page = alloc_pages_node(iommu->nid, GFP_KERNEL, get_order(ptab_size));
      BUG_ON(!page);

      iommu->ptab = page_address(page);
      memset(iommu->ptab, 0, ptab_size);

      /* allocate a bogus page for the end of each mapping */
      page = alloc_pages_node(iommu->nid, GFP_KERNEL, 0);
      BUG_ON(!page);
      iommu->pad_page = page_address(page);
      clear_page(iommu->pad_page);

      /* number of pages needed for a page table */
      n_pte_pages = (pages_per_segment *
                   sizeof(unsigned long)) >> IOMMU_PAGE_SHIFT;

      pr_debug("%s: iommu[%d]: stab at %p, ptab at %p, n_pte_pages: %lu\n",
                  __FUNCTION__, iommu->nid, iommu->stab, iommu->ptab,
                  n_pte_pages);

      /* initialise the STEs */
      reg = IOSTE_V | ((n_pte_pages - 1) << 5);

      if (IOMMU_PAGE_SIZE == 0x1000)
            reg |= IOSTE_PS_4K;
      else if (IOMMU_PAGE_SIZE == 0x10000)
            reg |= IOSTE_PS_64K;
      else {
            extern void __unknown_page_size_error(void);
            __unknown_page_size_error();
      }

      pr_debug("Setting up IOMMU stab:\n");
      for (i = 0; i * (1ul << IO_SEGMENT_SHIFT) < size; i++) {
            iommu->stab[i] = reg |
                  (__pa(iommu->ptab) + n_pte_pages * IOMMU_PAGE_SIZE * i);
            pr_debug("\t[%d] 0x%016lx\n", i, iommu->stab[i]);
      }

      /* ensure that the STEs have updated */
      mb();

      /* setup interrupts for the iommu. */
      reg = in_be64(iommu->xlate_regs + IOC_IO_ExcpStat);
      out_be64(iommu->xlate_regs + IOC_IO_ExcpStat,
                  reg & ~IOC_IO_ExcpStat_V);
      out_be64(iommu->xlate_regs + IOC_IO_ExcpMask,
                  IOC_IO_ExcpMask_PFE | IOC_IO_ExcpMask_SFE);

      virq = irq_create_mapping(NULL,
                  IIC_IRQ_IOEX_ATI | (iommu->nid << IIC_IRQ_NODE_SHIFT));
      BUG_ON(virq == NO_IRQ);

      ret = request_irq(virq, ioc_interrupt, IRQF_DISABLED,
                  iommu->name, iommu);
      BUG_ON(ret);

      /* set the IOC segment table origin register (and turn on the iommu) */
      reg = IOC_IOST_Origin_E | __pa(iommu->stab) | IOC_IOST_Origin_HW;
      out_be64(iommu->xlate_regs + IOC_IOST_Origin, reg);
      in_be64(iommu->xlate_regs + IOC_IOST_Origin);

      /* turn on IO translation */
      reg = in_be64(iommu->cmd_regs + IOC_IOCmd_Cfg) | IOC_IOCmd_Cfg_TE;
      out_be64(iommu->cmd_regs + IOC_IOCmd_Cfg, reg);
}

#if 0/* Unused for now */
static struct iommu_window *find_window(struct cbe_iommu *iommu,
            unsigned long offset, unsigned long size)
{
      struct iommu_window *window;

      /* todo: check for overlapping (but not equal) windows) */

      list_for_each_entry(window, &(iommu->windows), list) {
            if (window->offset == offset && window->size == size)
                  return window;
      }

      return NULL;
}
#endif

static struct iommu_window * __init
cell_iommu_setup_window(struct cbe_iommu *iommu, struct device_node *np,
                  unsigned long offset, unsigned long size,
                  unsigned long pte_offset)
{
      struct iommu_window *window;
      const unsigned int *ioid;

      ioid = of_get_property(np, "ioid", NULL);
      if (ioid == NULL)
            printk(KERN_WARNING "iommu: missing ioid for %s using 0\n",
                   np->full_name);

      window = kmalloc_node(sizeof(*window), GFP_KERNEL, iommu->nid);
      BUG_ON(window == NULL);

      window->offset = offset;
      window->size = size;
      window->ioid = ioid ? *ioid : 0;
      window->iommu = iommu;
      window->pte_offset = pte_offset;

      window->table.it_blocksize = 16;
      window->table.it_base = (unsigned long)iommu->ptab;
      window->table.it_index = iommu->nid;
      window->table.it_offset = (offset >> IOMMU_PAGE_SHIFT) +
            window->pte_offset;
      window->table.it_size = size >> IOMMU_PAGE_SHIFT;

      iommu_init_table(&window->table, iommu->nid);

      pr_debug("\tioid      %d\n", window->ioid);
      pr_debug("\tblocksize %ld\n", window->table.it_blocksize);
      pr_debug("\tbase      0x%016lx\n", window->table.it_base);
      pr_debug("\toffset    0x%lx\n", window->table.it_offset);
      pr_debug("\tsize      %ld\n", window->table.it_size);

      list_add(&window->list, &iommu->windows);

      if (offset != 0)
            return window;

      /* We need to map and reserve the first IOMMU page since it's used
       * by the spider workaround. In theory, we only need to do that when
       * running on spider but it doesn't really matter.
       *
       * This code also assumes that we have a window that starts at 0,
       * which is the case on all spider based blades.
       */
      __set_bit(0, window->table.it_map);
      tce_build_cell(&window->table, window->table.it_offset, 1,
                   (unsigned long)iommu->pad_page, DMA_TO_DEVICE);
      window->table.it_hint = window->table.it_blocksize;

      return window;
}

static struct cbe_iommu *cell_iommu_for_node(int nid)
{
      int i;

      for (i = 0; i < cbe_nr_iommus; i++)
            if (iommus[i].nid == nid)
                  return &iommus[i];
      return NULL;
}

static void cell_dma_dev_setup(struct device *dev)
{
      struct iommu_window *window;
      struct cbe_iommu *iommu;
      struct dev_archdata *archdata = &dev->archdata;

      /* If we run without iommu, no need to do anything */
      if (get_pci_dma_ops() == &dma_direct_ops)
            return;

      /* Current implementation uses the first window available in that
       * node's iommu. We -might- do something smarter later though it may
       * never be necessary
       */
      iommu = cell_iommu_for_node(archdata->numa_node);
      if (iommu == NULL || list_empty(&iommu->windows)) {
            printk(KERN_ERR "iommu: missing iommu for %s (node %d)\n",
                   archdata->of_node ? archdata->of_node->full_name : "?",
                   archdata->numa_node);
            return;
      }
      window = list_entry(iommu->windows.next, struct iommu_window, list);

      archdata->dma_data = &window->table;
}

static void cell_pci_dma_dev_setup(struct pci_dev *dev)
{
      cell_dma_dev_setup(&dev->dev);
}

static int cell_of_bus_notify(struct notifier_block *nb, unsigned long action,
                        void *data)
{
      struct device *dev = data;

      /* We are only intereted in device addition */
      if (action != BUS_NOTIFY_ADD_DEVICE)
            return 0;

      /* We use the PCI DMA ops */
      dev->archdata.dma_ops = get_pci_dma_ops();

      cell_dma_dev_setup(dev);

      return 0;
}

static struct notifier_block cell_of_bus_notifier = {
      .notifier_call = cell_of_bus_notify
};

static int __init cell_iommu_get_window(struct device_node *np,
                               unsigned long *base,
                               unsigned long *size)
{
      const void *dma_window;
      unsigned long index;

      /* Use ibm,dma-window if available, else, hard code ! */
      dma_window = of_get_property(np, "ibm,dma-window", NULL);
      if (dma_window == NULL) {
            *base = 0;
            *size = 0x80000000u;
            return -ENODEV;
      }

      of_parse_dma_window(np, dma_window, &index, base, size);
      return 0;
}

static void __init cell_iommu_init_one(struct device_node *np, unsigned long offset)
{
      struct cbe_iommu *iommu;
      unsigned long base, size;
      int nid, i;

      /* Get node ID */
      nid = of_node_to_nid(np);
      if (nid < 0) {
            printk(KERN_ERR "iommu: failed to get node for %s\n",
                   np->full_name);
            return;
      }
      pr_debug("iommu: setting up iommu for node %d (%s)\n",
             nid, np->full_name);

      /* XXX todo: If we can have multiple windows on the same IOMMU, which
       * isn't the case today, we probably want here to check wether the
       * iommu for that node is already setup.
       * However, there might be issue with getting the size right so let's
       * ignore that for now. We might want to completely get rid of the
       * multiple window support since the cell iommu supports per-page ioids
       */

      if (cbe_nr_iommus >= NR_IOMMUS) {
            printk(KERN_ERR "iommu: too many IOMMUs detected ! (%s)\n",
                   np->full_name);
            return;
      }

      /* Init base fields */
      i = cbe_nr_iommus++;
      iommu = &iommus[i];
      iommu->stab = NULL;
      iommu->nid = nid;
      snprintf(iommu->name, sizeof(iommu->name), "iommu%d", i);
      INIT_LIST_HEAD(&iommu->windows);

      /* Obtain a window for it */
      cell_iommu_get_window(np, &base, &size);

      pr_debug("\ttranslating window 0x%lx...0x%lx\n",
             base, base + size - 1);

      /* Initialize the hardware */
      cell_iommu_setup_hardware(iommu, size);

      /* Setup the iommu_table */
      cell_iommu_setup_window(iommu, np, base, size,
                        offset >> IOMMU_PAGE_SHIFT);
}

static void __init cell_disable_iommus(void)
{
      int node;
      unsigned long base, val;
      void __iomem *xregs, *cregs;

      /* Make sure IOC translation is disabled on all nodes */
      for_each_online_node(node) {
            if (cell_iommu_find_ioc(node, &base))
                  continue;
            xregs = ioremap(base, IOC_Reg_Size);
            if (xregs == NULL)
                  continue;
            cregs = xregs + IOC_IOCmd_Offset;

            pr_debug("iommu: cleaning up iommu on node %d\n", node);

            out_be64(xregs + IOC_IOST_Origin, 0);
            (void)in_be64(xregs + IOC_IOST_Origin);
            val = in_be64(cregs + IOC_IOCmd_Cfg);
            val &= ~IOC_IOCmd_Cfg_TE;
            out_be64(cregs + IOC_IOCmd_Cfg, val);
            (void)in_be64(cregs + IOC_IOCmd_Cfg);

            iounmap(xregs);
      }
}

static int __init cell_iommu_init_disabled(void)
{
      struct device_node *np = NULL;
      unsigned long base = 0, size;

      /* When no iommu is present, we use direct DMA ops */
      set_pci_dma_ops(&dma_direct_ops);

      /* First make sure all IOC translation is turned off */
      cell_disable_iommus();

      /* If we have no Axon, we set up the spider DMA magic offset */
      if (of_find_node_by_name(NULL, "axon") == NULL)
            dma_direct_offset = SPIDER_DMA_OFFSET;

      /* Now we need to check to see where the memory is mapped
       * in PCI space. We assume that all busses use the same dma
       * window which is always the case so far on Cell, thus we
       * pick up the first pci-internal node we can find and check
       * the DMA window from there.
       */
      for_each_node_by_name(np, "axon") {
            if (np->parent == NULL || np->parent->parent != NULL)
                  continue;
            if (cell_iommu_get_window(np, &base, &size) == 0)
                  break;
      }
      if (np == NULL) {
            for_each_node_by_name(np, "pci-internal") {
                  if (np->parent == NULL || np->parent->parent != NULL)
                        continue;
                  if (cell_iommu_get_window(np, &base, &size) == 0)
                        break;
            }
      }
      of_node_put(np);

      /* If we found a DMA window, we check if it's big enough to enclose
       * all of physical memory. If not, we force enable IOMMU
       */
      if (np && size < lmb_end_of_DRAM()) {
            printk(KERN_WARNING "iommu: force-enabled, dma window"
                   " (%ldMB) smaller than total memory (%ldMB)\n",
                   size >> 20, lmb_end_of_DRAM() >> 20);
            return -ENODEV;
      }

      dma_direct_offset += base;

      printk("iommu: disabled, direct DMA offset is 0x%lx\n",
             dma_direct_offset);

      return 0;
}

static int __init cell_iommu_init(void)
{
      struct device_node *np;

      if (!machine_is(cell))
            return -ENODEV;

      /* If IOMMU is disabled or we have little enough RAM to not need
       * to enable it, we setup a direct mapping.
       *
       * Note: should we make sure we have the IOMMU actually disabled ?
       */
      if (iommu_is_off ||
          (!iommu_force_on && lmb_end_of_DRAM() <= 0x80000000ull))
            if (cell_iommu_init_disabled() == 0)
                  goto bail;

      /* Setup various ppc_md. callbacks */
      ppc_md.pci_dma_dev_setup = cell_pci_dma_dev_setup;
      ppc_md.tce_build = tce_build_cell;
      ppc_md.tce_free = tce_free_cell;

      /* Create an iommu for each /axon node.  */
      for_each_node_by_name(np, "axon") {
            if (np->parent == NULL || np->parent->parent != NULL)
                  continue;
            cell_iommu_init_one(np, 0);
      }

      /* Create an iommu for each toplevel /pci-internal node for
       * old hardware/firmware
       */
      for_each_node_by_name(np, "pci-internal") {
            if (np->parent == NULL || np->parent->parent != NULL)
                  continue;
            cell_iommu_init_one(np, SPIDER_DMA_OFFSET);
      }

      /* Setup default PCI iommu ops */
      set_pci_dma_ops(&dma_iommu_ops);

 bail:
      /* Register callbacks on OF platform device addition/removal
       * to handle linking them to the right DMA operations
       */
      bus_register_notifier(&of_platform_bus_type, &cell_of_bus_notifier);

      return 0;
}
arch_initcall(cell_iommu_init);


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