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linux-zen-server/arch/alpha/kernel/core_titan.c

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Initial commit
2023-08-30 17:53:23 +02:00
// SPDX-License-Identifier: GPL-2.0
/*
* 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/memblock.h>
#include <asm/ptrace.h>
#include <asm/smp.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
/*
* 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;
}
/*
* 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,
};
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,
SMP_CACHE_BYTES);
hose->sg_isa->align_entry = 8; /* 64KB for ISA */
hose->sg_pci = iommu_arena_new(hose, 0xc0000000, 0x40000000,
SMP_CACHE_BYTES);
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);
}
/*
* 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;
#ifdef CONFIG_VGA_HOSE
/*
* 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;
}
#endif
/*
* 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
/*
* 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;
}