ARM: mmp: fix potential NULL dereference

[linux/fpc-iii.git] / arch / alpha / kernel / core_titan.c

/*
 *      linux/arch/alpha/kernel/core_titan.c
 *
 * Code common to all TITAN core logic chips.
 */

#define __EXTERN_INLINE inline
#include <asm/io.h>
#include <asm/core_titan.h>
#undef __EXTERN_INLINE

#include <linux/module.h>
#include <linux/types.h>
#include <linux/pci.h>
#include <linux/sched.h>
#include <linux/init.h>
#include <linux/vmalloc.h>
#include <linux/bootmem.h>

#include <asm/ptrace.h>
#include <asm/smp.h>
#include <asm/pgalloc.h>
#include <asm/tlbflush.h>
#include <asm/vga.h>

#include "proto.h"
#include "pci_impl.h"

/* Save Titan configuration data as the console had it set up.  */

struct
{
        unsigned long wsba[4];
        unsigned long wsm[4];
        unsigned long tba[4];
} saved_config[4] __attribute__((common));

/*
 * Is PChip 1 present? No need to query it more than once.
 */
static int titan_pchip1_present;

/*
 * BIOS32-style PCI interface:
 */

#define DEBUG_CONFIG 0

#if DEBUG_CONFIG
# define DBG_CFG(args)  printk args
#else
# define DBG_CFG(args)
#endif

\f
/*
 * Routines to access TIG registers.
 */
static inline volatile unsigned long *
mk_tig_addr(int offset)
{
        return (volatile unsigned long *)(TITAN_TIG_SPACE + (offset << 6));
}

static inline u8 
titan_read_tig(int offset, u8 value)
{
        volatile unsigned long *tig_addr = mk_tig_addr(offset);
        return (u8)(*tig_addr & 0xff);
}

static inline void 
titan_write_tig(int offset, u8 value)
{
        volatile unsigned long *tig_addr = mk_tig_addr(offset);
        *tig_addr = (unsigned long)value;
}

\f
/*
 * Given a bus, device, and function number, compute resulting
 * configuration space address
 * accordingly.  It is therefore not safe to have concurrent
 * invocations to configuration space access routines, but there
 * really shouldn't be any need for this.
 *
 * Note that all config space accesses use Type 1 address format.
 *
 * Note also that type 1 is determined by non-zero bus number.
 *
 * Type 1:
 *
 *  3 3|3 3 2 2|2 2 2 2|2 2 2 2|1 1 1 1|1 1 1 1|1 1 
 *  3 2|1 0 9 8|7 6 5 4|3 2 1 0|9 8 7 6|5 4 3 2|1 0 9 8|7 6 5 4|3 2 1 0
 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 * | | | | | | | | | | |B|B|B|B|B|B|B|B|D|D|D|D|D|F|F|F|R|R|R|R|R|R|0|1|
 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 *
 *      31:24   reserved
 *      23:16   bus number (8 bits = 128 possible buses)
 *      15:11   Device number (5 bits)
 *      10:8    function number
 *       7:2    register number
 *  
 * Notes:
 *      The function number selects which function of a multi-function device 
 *      (e.g., SCSI and Ethernet).
 * 
 *      The register selects a DWORD (32 bit) register offset.  Hence it
 *      doesn't get shifted by 2 bits as we want to "drop" the bottom two
 *      bits.
 */

static int
mk_conf_addr(struct pci_bus *pbus, unsigned int device_fn, int where,
             unsigned long *pci_addr, unsigned char *type1)
{
        struct pci_controller *hose = pbus->sysdata;
        unsigned long addr;
        u8 bus = pbus->number;

        DBG_CFG(("mk_conf_addr(bus=%d ,device_fn=0x%x, where=0x%x, "
                 "pci_addr=0x%p, type1=0x%p)\n",
                 bus, device_fn, where, pci_addr, type1));

        if (!pbus->parent) /* No parent means peer PCI bus. */
                bus = 0;
        *type1 = (bus != 0);

        addr = (bus << 16) | (device_fn << 8) | where;
        addr |= hose->config_space_base;
                
        *pci_addr = addr;
        DBG_CFG(("mk_conf_addr: returning pci_addr 0x%lx\n", addr));
        return 0;
}

static int
titan_read_config(struct pci_bus *bus, unsigned int devfn, int where,
                  int size, u32 *value)
{
        unsigned long addr;
        unsigned char type1;

        if (mk_conf_addr(bus, devfn, where, &addr, &type1))
                return PCIBIOS_DEVICE_NOT_FOUND;

        switch (size) {
        case 1:
                *value = __kernel_ldbu(*(vucp)addr);
                break;
        case 2:
                *value = __kernel_ldwu(*(vusp)addr);
                break;
        case 4:
                *value = *(vuip)addr;
                break;
        }

        return PCIBIOS_SUCCESSFUL;
}

static int 
titan_write_config(struct pci_bus *bus, unsigned int devfn, int where,
                   int size, u32 value)
{
        unsigned long addr;
        unsigned char type1;

        if (mk_conf_addr(bus, devfn, where, &addr, &type1))
                return PCIBIOS_DEVICE_NOT_FOUND;

        switch (size) {
        case 1:
                __kernel_stb(value, *(vucp)addr);
                mb();
                __kernel_ldbu(*(vucp)addr);
                break;
        case 2:
                __kernel_stw(value, *(vusp)addr);
                mb();
                __kernel_ldwu(*(vusp)addr);
                break;
        case 4:
                *(vuip)addr = value;
                mb();
                *(vuip)addr;
                break;
        }

        return PCIBIOS_SUCCESSFUL;
}

struct pci_ops titan_pci_ops = 
{
        .read =         titan_read_config,
        .write =        titan_write_config,
};

\f
void
titan_pci_tbi(struct pci_controller *hose, dma_addr_t start, dma_addr_t end)
{
        titan_pachip *pachip = 
          (hose->index & 1) ? TITAN_pachip1 : TITAN_pachip0;
        titan_pachip_port *port;
        volatile unsigned long *csr;
        unsigned long value;

        /* Get the right hose.  */
        port = &pachip->g_port;
        if (hose->index & 2) 
                port = &pachip->a_port;

        /* We can invalidate up to 8 tlb entries in a go.  The flush
           matches against <31:16> in the pci address.  
           Note that gtlbi* and atlbi* are in the same place in the g_port
           and a_port, respectively, so the g_port offset can be used
           even if hose is an a_port */
        csr = &port->port_specific.g.gtlbia.csr;
        if (((start ^ end) & 0xffff0000) == 0)
                csr = &port->port_specific.g.gtlbiv.csr;

        /* For TBIA, it doesn't matter what value we write.  For TBI, 
           it's the shifted tag bits.  */
        value = (start & 0xffff0000) >> 12;

        wmb();
        *csr = value;
        mb();
        *csr;
}

static int
titan_query_agp(titan_pachip_port *port)
{
        union TPAchipPCTL pctl;

        /* set up APCTL */
        pctl.pctl_q_whole = port->pctl.csr;

        return pctl.pctl_r_bits.apctl_v_agp_present;

}

static void __init
titan_init_one_pachip_port(titan_pachip_port *port, int index)
{
        struct pci_controller *hose;

        hose = alloc_pci_controller();
        if (index == 0)
                pci_isa_hose = hose;
        hose->io_space = alloc_resource();
        hose->mem_space = alloc_resource();

        /*
         * This is for userland consumption.  The 40-bit PIO bias that we 
         * use in the kernel through KSEG doesn't work in the page table 
         * based user mappings. (43-bit KSEG sign extends the physical
         * address from bit 40 to hit the I/O bit - mapped addresses don't).
         * So make sure we get the 43-bit PIO bias.  
         */
        hose->sparse_mem_base = 0;
        hose->sparse_io_base = 0;
        hose->dense_mem_base
          = (TITAN_MEM(index) & 0xffffffffffUL) | 0x80000000000UL;
        hose->dense_io_base
          = (TITAN_IO(index) & 0xffffffffffUL) | 0x80000000000UL;

        hose->config_space_base = TITAN_CONF(index);
        hose->index = index;

        hose->io_space->start = TITAN_IO(index) - TITAN_IO_BIAS;
        hose->io_space->end = hose->io_space->start + TITAN_IO_SPACE - 1;
        hose->io_space->name = pci_io_names[index];
        hose->io_space->flags = IORESOURCE_IO;

        hose->mem_space->start = TITAN_MEM(index) - TITAN_MEM_BIAS;
        hose->mem_space->end = hose->mem_space->start + 0xffffffff;
        hose->mem_space->name = pci_mem_names[index];
        hose->mem_space->flags = IORESOURCE_MEM;

        if (request_resource(&ioport_resource, hose->io_space) < 0)
                printk(KERN_ERR "Failed to request IO on hose %d\n", index);
        if (request_resource(&iomem_resource, hose->mem_space) < 0)
                printk(KERN_ERR "Failed to request MEM on hose %d\n", index);

        /*
         * Save the existing PCI window translations.  SRM will 
         * need them when we go to reboot.
         */
        saved_config[index].wsba[0] = port->wsba[0].csr;
        saved_config[index].wsm[0]  = port->wsm[0].csr;
        saved_config[index].tba[0]  = port->tba[0].csr;

        saved_config[index].wsba[1] = port->wsba[1].csr;
        saved_config[index].wsm[1]  = port->wsm[1].csr;
        saved_config[index].tba[1]  = port->tba[1].csr;

        saved_config[index].wsba[2] = port->wsba[2].csr;
        saved_config[index].wsm[2]  = port->wsm[2].csr;
        saved_config[index].tba[2]  = port->tba[2].csr;

        saved_config[index].wsba[3] = port->wsba[3].csr;
        saved_config[index].wsm[3]  = port->wsm[3].csr;
        saved_config[index].tba[3]  = port->tba[3].csr;

        /*
         * Set up the PCI to main memory translation windows.
         *
         * Note: Window 3 on Titan is Scatter-Gather ONLY.
         *
         * Window 0 is scatter-gather 8MB at 8MB (for isa)
         * Window 1 is direct access 1GB at 2GB
         * Window 2 is scatter-gather 1GB at 3GB
         */
        hose->sg_isa = iommu_arena_new(hose, 0x00800000, 0x00800000, 0);
        hose->sg_isa->align_entry = 8; /* 64KB for ISA */

        hose->sg_pci = iommu_arena_new(hose, 0xc0000000, 0x40000000, 0);
        hose->sg_pci->align_entry = 4; /* Titan caches 4 PTEs at a time */

        port->wsba[0].csr = hose->sg_isa->dma_base | 3;
        port->wsm[0].csr  = (hose->sg_isa->size - 1) & 0xfff00000;
        port->tba[0].csr  = virt_to_phys(hose->sg_isa->ptes);

        port->wsba[1].csr = __direct_map_base | 1;
        port->wsm[1].csr  = (__direct_map_size - 1) & 0xfff00000;
        port->tba[1].csr  = 0;

        port->wsba[2].csr = hose->sg_pci->dma_base | 3;
        port->wsm[2].csr  = (hose->sg_pci->size - 1) & 0xfff00000;
        port->tba[2].csr  = virt_to_phys(hose->sg_pci->ptes);

        port->wsba[3].csr = 0;

        /* Enable the Monster Window to make DAC pci64 possible.  */
        port->pctl.csr |= pctl_m_mwin;

        /*
         * If it's an AGP port, initialize agplastwr.
         */
        if (titan_query_agp(port)) 
                port->port_specific.a.agplastwr.csr = __direct_map_base;

        titan_pci_tbi(hose, 0, -1);
}

static void __init
titan_init_pachips(titan_pachip *pachip0, titan_pachip *pachip1)
{
        titan_pchip1_present = TITAN_cchip->csc.csr & 1L<<14;

        /* Init the ports in hose order... */
        titan_init_one_pachip_port(&pachip0->g_port, 0);        /* hose 0 */
        if (titan_pchip1_present)
                titan_init_one_pachip_port(&pachip1->g_port, 1);/* hose 1 */
        titan_init_one_pachip_port(&pachip0->a_port, 2);        /* hose 2 */
        if (titan_pchip1_present)
                titan_init_one_pachip_port(&pachip1->a_port, 3);/* hose 3 */
}

void __init
titan_init_arch(void)
{
#if 0
        printk("%s: titan_init_arch()\n", __func__);
        printk("%s: CChip registers:\n", __func__);
        printk("%s: CSR_CSC 0x%lx\n", __func__, TITAN_cchip->csc.csr);
        printk("%s: CSR_MTR 0x%lx\n", __func__, TITAN_cchip->mtr.csr);
        printk("%s: CSR_MISC 0x%lx\n", __func__, TITAN_cchip->misc.csr);
        printk("%s: CSR_DIM0 0x%lx\n", __func__, TITAN_cchip->dim0.csr);
        printk("%s: CSR_DIM1 0x%lx\n", __func__, TITAN_cchip->dim1.csr);
        printk("%s: CSR_DIR0 0x%lx\n", __func__, TITAN_cchip->dir0.csr);
        printk("%s: CSR_DIR1 0x%lx\n", __func__, TITAN_cchip->dir1.csr);
        printk("%s: CSR_DRIR 0x%lx\n", __func__, TITAN_cchip->drir.csr);

        printk("%s: DChip registers:\n", __func__);
        printk("%s: CSR_DSC 0x%lx\n", __func__, TITAN_dchip->dsc.csr);
        printk("%s: CSR_STR 0x%lx\n", __func__, TITAN_dchip->str.csr);
        printk("%s: CSR_DREV 0x%lx\n", __func__, TITAN_dchip->drev.csr);
#endif

        boot_cpuid = __hard_smp_processor_id();

        /* With multiple PCI busses, we play with I/O as physical addrs.  */
        ioport_resource.end = ~0UL;
        iomem_resource.end = ~0UL;

        /* PCI DMA Direct Mapping is 1GB at 2GB.  */
        __direct_map_base = 0x80000000;
        __direct_map_size = 0x40000000;

        /* Init the PA chip(s).  */
        titan_init_pachips(TITAN_pachip0, TITAN_pachip1);

        /* Check for graphic console location (if any).  */
        find_console_vga_hose();
}

static void
titan_kill_one_pachip_port(titan_pachip_port *port, int index)
{
        port->wsba[0].csr = saved_config[index].wsba[0];
        port->wsm[0].csr  = saved_config[index].wsm[0];
        port->tba[0].csr  = saved_config[index].tba[0];

        port->wsba[1].csr = saved_config[index].wsba[1];
        port->wsm[1].csr  = saved_config[index].wsm[1];
        port->tba[1].csr  = saved_config[index].tba[1];

        port->wsba[2].csr = saved_config[index].wsba[2];
        port->wsm[2].csr  = saved_config[index].wsm[2];
        port->tba[2].csr  = saved_config[index].tba[2];

        port->wsba[3].csr = saved_config[index].wsba[3];
        port->wsm[3].csr  = saved_config[index].wsm[3];
        port->tba[3].csr  = saved_config[index].tba[3];
}

static void
titan_kill_pachips(titan_pachip *pachip0, titan_pachip *pachip1)
{
        if (titan_pchip1_present) {
                titan_kill_one_pachip_port(&pachip1->g_port, 1);
                titan_kill_one_pachip_port(&pachip1->a_port, 3);
        }
        titan_kill_one_pachip_port(&pachip0->g_port, 0);
        titan_kill_one_pachip_port(&pachip0->a_port, 2);
}

void
titan_kill_arch(int mode)
{
        titan_kill_pachips(TITAN_pachip0, TITAN_pachip1);
}

\f
/*
 * IO map support.
 */

void __iomem *
titan_ioportmap(unsigned long addr)
{
        FIXUP_IOADDR_VGA(addr);
        return (void __iomem *)(addr + TITAN_IO_BIAS);
}


void __iomem *
titan_ioremap(unsigned long addr, unsigned long size)
{
        int h = (addr & TITAN_HOSE_MASK) >> TITAN_HOSE_SHIFT;
        unsigned long baddr = addr & ~TITAN_HOSE_MASK;
        unsigned long last = baddr + size - 1;
        struct pci_controller *hose;    
        struct vm_struct *area;
        unsigned long vaddr;
        unsigned long *ptes;
        unsigned long pfn;

        /*
         * Adjust the address and hose, if necessary.
         */ 
        if (pci_vga_hose && __is_mem_vga(addr)) {
                h = pci_vga_hose->index;
                addr += pci_vga_hose->mem_space->start;
        }

        /*
         * Find the hose.
         */
        for (hose = hose_head; hose; hose = hose->next)
                if (hose->index == h)
                        break;
        if (!hose)
                return NULL;

        /*
         * Is it direct-mapped?
         */
        if ((baddr >= __direct_map_base) && 
            ((baddr + size - 1) < __direct_map_base + __direct_map_size)) {
                vaddr = addr - __direct_map_base + TITAN_MEM_BIAS;
                return (void __iomem *) vaddr;
        }

        /* 
         * Check the scatter-gather arena.
         */
        if (hose->sg_pci &&
            baddr >= (unsigned long)hose->sg_pci->dma_base &&
            last < (unsigned long)hose->sg_pci->dma_base + hose->sg_pci->size){

                /*
                 * Adjust the limits (mappings must be page aligned)
                 */
                baddr -= hose->sg_pci->dma_base;
                last -= hose->sg_pci->dma_base;
                baddr &= PAGE_MASK;
                size = PAGE_ALIGN(last) - baddr;

                /*
                 * Map it
                 */
                area = get_vm_area(size, VM_IOREMAP);
                if (!area) {
                        printk("ioremap failed... no vm_area...\n");
                        return NULL;
                }

                ptes = hose->sg_pci->ptes;
                for (vaddr = (unsigned long)area->addr; 
                    baddr <= last; 
                    baddr += PAGE_SIZE, vaddr += PAGE_SIZE) {
                        pfn = ptes[baddr >> PAGE_SHIFT];
                        if (!(pfn & 1)) {
                                printk("ioremap failed... pte not valid...\n");
                                vfree(area->addr);
                                return NULL;
                        }
                        pfn >>= 1;      /* make it a true pfn */
                        
                        if (__alpha_remap_area_pages(vaddr,
                                                     pfn << PAGE_SHIFT, 
                                                     PAGE_SIZE, 0)) {
                                printk("FAILED to remap_area_pages...\n");
                                vfree(area->addr);
                                return NULL;
                        }
                }

                flush_tlb_all();

                vaddr = (unsigned long)area->addr + (addr & ~PAGE_MASK);
                return (void __iomem *) vaddr;
        }

        /* Assume a legacy (read: VGA) address, and return appropriately. */
        return (void __iomem *)(addr + TITAN_MEM_BIAS);
}

void
titan_iounmap(volatile void __iomem *xaddr)
{
        unsigned long addr = (unsigned long) xaddr;
        if (addr >= VMALLOC_START)
                vfree((void *)(PAGE_MASK & addr)); 
}

int
titan_is_mmio(const volatile void __iomem *xaddr)
{
        unsigned long addr = (unsigned long) xaddr;

        if (addr >= VMALLOC_START)
                return 1;
        else
                return (addr & 0x100000000UL) == 0;
}

#ifndef CONFIG_ALPHA_GENERIC
EXPORT_SYMBOL(titan_ioportmap);
EXPORT_SYMBOL(titan_ioremap);
EXPORT_SYMBOL(titan_iounmap);
EXPORT_SYMBOL(titan_is_mmio);
#endif
\f
/*
 * AGP GART Support.
 */
#include <linux/agp_backend.h>
#include <asm/agp_backend.h>
#include <linux/slab.h>
#include <linux/delay.h>

struct titan_agp_aperture {
        struct pci_iommu_arena *arena;
        long pg_start;
        long pg_count;
};

static int
titan_agp_setup(alpha_agp_info *agp)
{
        struct titan_agp_aperture *aper;

        if (!alpha_agpgart_size)
                return -ENOMEM;

        aper = kmalloc(sizeof(struct titan_agp_aperture), GFP_KERNEL);
        if (aper == NULL)
                return -ENOMEM;

        aper->arena = agp->hose->sg_pci;
        aper->pg_count = alpha_agpgart_size / PAGE_SIZE;
        aper->pg_start = iommu_reserve(aper->arena, aper->pg_count,
                                       aper->pg_count - 1);
        if (aper->pg_start < 0) {
                printk(KERN_ERR "Failed to reserve AGP memory\n");
                kfree(aper);
                return -ENOMEM;
        }

        agp->aperture.bus_base = 
                aper->arena->dma_base + aper->pg_start * PAGE_SIZE;
        agp->aperture.size = aper->pg_count * PAGE_SIZE;
        agp->aperture.sysdata = aper;

        return 0;
}

static void
titan_agp_cleanup(alpha_agp_info *agp)
{
        struct titan_agp_aperture *aper = agp->aperture.sysdata;
        int status;

        status = iommu_release(aper->arena, aper->pg_start, aper->pg_count);
        if (status == -EBUSY) {
                printk(KERN_WARNING 
                       "Attempted to release bound AGP memory - unbinding\n");
                iommu_unbind(aper->arena, aper->pg_start, aper->pg_count);
                status = iommu_release(aper->arena, aper->pg_start, 
                                       aper->pg_count);
        }
        if (status < 0)
                printk(KERN_ERR "Failed to release AGP memory\n");

        kfree(aper);
        kfree(agp);
}

static int
titan_agp_configure(alpha_agp_info *agp)
{
        union TPAchipPCTL pctl;
        titan_pachip_port *port = agp->private;
        pctl.pctl_q_whole = port->pctl.csr;

        /* Side-Band Addressing? */
        pctl.pctl_r_bits.apctl_v_agp_sba_en = agp->mode.bits.sba;

        /* AGP Rate? */
        pctl.pctl_r_bits.apctl_v_agp_rate = 0;          /* 1x */
        if (agp->mode.bits.rate & 2) 
                pctl.pctl_r_bits.apctl_v_agp_rate = 1;  /* 2x */
#if 0
        if (agp->mode.bits.rate & 4) 
                pctl.pctl_r_bits.apctl_v_agp_rate = 2;  /* 4x */
#endif
        
        /* RQ Depth? */
        pctl.pctl_r_bits.apctl_v_agp_hp_rd = 2;
        pctl.pctl_r_bits.apctl_v_agp_lp_rd = 7;

        /*
         * AGP Enable.
         */
        pctl.pctl_r_bits.apctl_v_agp_en = agp->mode.bits.enable;

        /* Tell the user.  */
        printk("Enabling AGP: %dX%s\n", 
               1 << pctl.pctl_r_bits.apctl_v_agp_rate,
               pctl.pctl_r_bits.apctl_v_agp_sba_en ? " - SBA" : "");
               
        /* Write it.  */
        port->pctl.csr = pctl.pctl_q_whole;
        
        /* And wait at least 5000 66MHz cycles (per Titan spec).  */
        udelay(100);

        return 0;
}

static int 
titan_agp_bind_memory(alpha_agp_info *agp, off_t pg_start, struct agp_memory *mem)
{
        struct titan_agp_aperture *aper = agp->aperture.sysdata;
        return iommu_bind(aper->arena, aper->pg_start + pg_start, 
                          mem->page_count, mem->pages);
}

static int 
titan_agp_unbind_memory(alpha_agp_info *agp, off_t pg_start, struct agp_memory *mem)
{
        struct titan_agp_aperture *aper = agp->aperture.sysdata;
        return iommu_unbind(aper->arena, aper->pg_start + pg_start,
                            mem->page_count);
}

static unsigned long
titan_agp_translate(alpha_agp_info *agp, dma_addr_t addr)
{
        struct titan_agp_aperture *aper = agp->aperture.sysdata;
        unsigned long baddr = addr - aper->arena->dma_base;
        unsigned long pte;

        if (addr < agp->aperture.bus_base ||
            addr >= agp->aperture.bus_base + agp->aperture.size) {
                printk("%s: addr out of range\n", __func__);
                return -EINVAL;
        }

        pte = aper->arena->ptes[baddr >> PAGE_SHIFT];
        if (!(pte & 1)) {
                printk("%s: pte not valid\n", __func__);
                return -EINVAL;
        }

        return (pte >> 1) << PAGE_SHIFT;
}

struct alpha_agp_ops titan_agp_ops =
{
        .setup          = titan_agp_setup,
        .cleanup        = titan_agp_cleanup,
        .configure      = titan_agp_configure,
        .bind           = titan_agp_bind_memory,
        .unbind         = titan_agp_unbind_memory,
        .translate      = titan_agp_translate
};

alpha_agp_info *
titan_agp_info(void)
{
        alpha_agp_info *agp;
        struct pci_controller *hose;
        titan_pachip_port *port;
        int hosenum = -1;
        union TPAchipPCTL pctl;

        /*
         * Find the AGP port.
         */
        port = &TITAN_pachip0->a_port;
        if (titan_query_agp(port))
                hosenum = 2;
        if (hosenum < 0 && 
            titan_pchip1_present &&
            titan_query_agp(port = &TITAN_pachip1->a_port)) 
                hosenum = 3;
        
        /*
         * Find the hose the port is on.
         */
        for (hose = hose_head; hose; hose = hose->next)
                if (hose->index == hosenum)
                        break;

        if (!hose || !hose->sg_pci)
                return NULL;

        /*
         * Allocate the info structure.
         */
        agp = kmalloc(sizeof(*agp), GFP_KERNEL);
        if (!agp)
                return NULL;

        /*
         * Fill it in.
         */
        agp->hose = hose;
        agp->private = port;
        agp->ops = &titan_agp_ops;

        /*
         * Aperture - not configured until ops.setup().
         *
         * FIXME - should we go ahead and allocate it here?
         */
        agp->aperture.bus_base = 0;
        agp->aperture.size = 0;
        agp->aperture.sysdata = NULL;

        /*
         * Capabilities.
         */
        agp->capability.lw = 0;
        agp->capability.bits.rate = 3;  /* 2x, 1x */
        agp->capability.bits.sba = 1;
        agp->capability.bits.rq = 7;    /* 8 - 1 */

        /*
         * Mode.
         */
        pctl.pctl_q_whole = port->pctl.csr;
        agp->mode.lw = 0;
        agp->mode.bits.rate = 1 << pctl.pctl_r_bits.apctl_v_agp_rate;
        agp->mode.bits.sba = pctl.pctl_r_bits.apctl_v_agp_sba_en;
        agp->mode.bits.rq = 7;  /* RQ Depth? */
        agp->mode.bits.enable = pctl.pctl_r_bits.apctl_v_agp_en;

        return agp;
}