mirror of
https://kernel.googlesource.com/pub/scm/linux/kernel/git/torvalds/linux
synced 2025-11-04 16:52:06 +10:00
0868ff7a42
My first guess for "fujitsu" was it might be related to the fujitsu-laptop.c driver... Move the frv directory one level up since frv is the name of the architecture in the Linux kernel. Signed-off-by: Adrian Bunk <bunk@kernel.org>
311 lines
11 KiB
Plaintext
311 lines
11 KiB
Plaintext
===========================
|
|
FUJITSU FR-V LINUX FEATURES
|
|
===========================
|
|
|
|
This kernel port has a number of features of which the user should be aware:
|
|
|
|
(*) Linux and uClinux
|
|
|
|
The FR-V architecture port supports both normal MMU linux and uClinux out
|
|
of the same sources.
|
|
|
|
|
|
(*) CPU support
|
|
|
|
Support for the FR401, FR403, FR405, FR451 and FR555 CPUs should work with
|
|
the same uClinux kernel configuration.
|
|
|
|
In normal (MMU) Linux mode, only the FR451 CPU will work as that is the
|
|
only one with a suitably featured CPU.
|
|
|
|
The kernel is written and compiled with the assumption that only the
|
|
bottom 32 GR registers and no FR registers will be used by the kernel
|
|
itself, however all extra userspace registers will be saved on context
|
|
switch. Note that since most CPUs can't support lazy switching, no attempt
|
|
is made to do lazy register saving where that would be possible (FR555
|
|
only currently).
|
|
|
|
|
|
(*) Board support
|
|
|
|
The board on which the kernel will run can be configured on the "Processor
|
|
type and features" configuration tab.
|
|
|
|
Set the System to "MB93093-PDK" to boot from the MB93093 (FR403) PDK.
|
|
|
|
Set the System to "MB93091-VDK" to boot from the CB11, CB30, CB41, CB60,
|
|
CB70 or CB451 VDK boards. Set the Motherboard setting to "MB93090-MB00" to
|
|
boot with the standard ATA90590B VDK motherboard, and set it to "None" to
|
|
boot without any motherboard.
|
|
|
|
|
|
(*) Binary Formats
|
|
|
|
The only userspace binary format supported is FDPIC ELF. Normal ELF, FLAT
|
|
and AOUT binaries are not supported for this architecture.
|
|
|
|
FDPIC ELF supports shared library and program interpreter facilities.
|
|
|
|
|
|
(*) Scheduler Speed
|
|
|
|
The kernel scheduler runs at 100Hz irrespective of the clock speed on this
|
|
architecture. This value is set in asm/param.h (see the HZ macro defined
|
|
there).
|
|
|
|
|
|
(*) Normal (MMU) Linux Memory Layout.
|
|
|
|
See mmu-layout.txt in this directory for a description of the normal linux
|
|
memory layout
|
|
|
|
See include/asm-frv/mem-layout.h for constants pertaining to the memory
|
|
layout.
|
|
|
|
See include/asm-frv/mb-regs.h for the constants pertaining to the I/O bus
|
|
controller configuration.
|
|
|
|
|
|
(*) uClinux Memory Layout
|
|
|
|
The memory layout used by the uClinux kernel is as follows:
|
|
|
|
0x00000000 - 0x00000FFF Null pointer catch page
|
|
0x20000000 - 0x200FFFFF CS2# [PDK] FPGA
|
|
0xC0000000 - 0xCFFFFFFF SDRAM
|
|
0xC0000000 Base of Linux kernel image
|
|
0xE0000000 - 0xEFFFFFFF CS2# [VDK] SLBUS/PCI window
|
|
0xF0000000 - 0xF0FFFFFF CS5# MB93493 CSC area (DAV daughter board)
|
|
0xF1000000 - 0xF1FFFFFF CS7# [CB70/CB451] CPU-card PCMCIA port space
|
|
0xFC000000 - 0xFC0FFFFF CS1# [VDK] MB86943 config space
|
|
0xFC100000 - 0xFC1FFFFF CS6# [CB70/CB451] CPU-card DM9000 NIC space
|
|
0xFC100000 - 0xFC1FFFFF CS6# [PDK] AX88796 NIC space
|
|
0xFC200000 - 0xFC2FFFFF CS3# MB93493 CSR area (DAV daughter board)
|
|
0xFD000000 - 0xFDFFFFFF CS4# [CB70/CB451] CPU-card extra flash space
|
|
0xFE000000 - 0xFEFFFFFF Internal CPU peripherals
|
|
0xFF000000 - 0xFF1FFFFF CS0# Flash 1
|
|
0xFF200000 - 0xFF3FFFFF CS0# Flash 2
|
|
0xFFC00000 - 0xFFC0001F CS0# [VDK] FPGA
|
|
|
|
The kernel reads the size of the SDRAM from the memory bus controller
|
|
registers by default.
|
|
|
|
The kernel initialisation code (1) adjusts the SDRAM base addresses to
|
|
move the SDRAM to desired address, (2) moves the kernel image down to the
|
|
bottom of SDRAM, (3) adjusts the bus controller registers to move I/O
|
|
windows, and (4) rearranges the protection registers to protect all of
|
|
this.
|
|
|
|
The reasons for doing this are: (1) the page at address 0 should be
|
|
inaccessible so that NULL pointer errors can be caught; and (2) the bottom
|
|
three quarters are left unoccupied so that an FR-V CPU with an MMU can use
|
|
it for virtual userspace mappings.
|
|
|
|
See include/asm-frv/mem-layout.h for constants pertaining to the memory
|
|
layout.
|
|
|
|
See include/asm-frv/mb-regs.h for the constants pertaining to the I/O bus
|
|
controller configuration.
|
|
|
|
|
|
(*) uClinux Memory Protection
|
|
|
|
A DAMPR register is used to cover the entire region used for I/O
|
|
(0xE0000000 - 0xFFFFFFFF). This permits the kernel to make uncached
|
|
accesses to this region. Userspace is not permitted to access it.
|
|
|
|
The DAMPR/IAMPR protection registers not in use for any other purpose are
|
|
tiled over the top of the SDRAM such that:
|
|
|
|
(1) The core kernel image is covered by as small a tile as possible
|
|
granting only the kernel access to the underlying data, whilst
|
|
making sure no SDRAM is actually made unavailable by this approach.
|
|
|
|
(2) All other tiles are arranged to permit userspace access to the rest
|
|
of the SDRAM.
|
|
|
|
Barring point (1), there is nothing to protect kernel data against
|
|
userspace damage - but this is uClinux.
|
|
|
|
|
|
(*) Exceptions and Fixups
|
|
|
|
Since the FR40x and FR55x CPUs that do not have full MMUs generate
|
|
imprecise data error exceptions, there are currently no automatic fixup
|
|
services available in uClinux. This includes misaligned memory access
|
|
fixups.
|
|
|
|
Userspace EFAULT errors can be trapped by issuing a MEMBAR instruction and
|
|
forcing the fault to happen there.
|
|
|
|
On the FR451, however, data exceptions are mostly precise, and so
|
|
exception fixup handling is implemented as normal.
|
|
|
|
|
|
(*) Userspace Breakpoints
|
|
|
|
The ptrace() system call supports the following userspace debugging
|
|
features:
|
|
|
|
(1) Hardware assisted single step.
|
|
|
|
(2) Breakpoint via the FR-V "BREAK" instruction.
|
|
|
|
(3) Breakpoint via the FR-V "TIRA GR0, #1" instruction.
|
|
|
|
(4) Syscall entry/exit trap.
|
|
|
|
Each of the above generates a SIGTRAP.
|
|
|
|
|
|
(*) On-Chip Serial Ports
|
|
|
|
The FR-V on-chip serial ports are made available as ttyS0 and ttyS1. Note
|
|
that if the GDB stub is compiled in, ttyS1 will not actually be available
|
|
as it will be being used for the GDB stub.
|
|
|
|
These ports can be made by:
|
|
|
|
mknod /dev/ttyS0 c 4 64
|
|
mknod /dev/ttyS1 c 4 65
|
|
|
|
|
|
(*) Maskable Interrupts
|
|
|
|
Level 15 (Non-maskable) interrupts are dealt with by the GDB stub if
|
|
present, and cause a panic if not. If the GDB stub is present, ttyS1's
|
|
interrupts are rated at level 15.
|
|
|
|
All other interrupts are distributed over the set of available priorities
|
|
so that no IRQs are shared where possible. The arch interrupt handling
|
|
routines attempt to disentangle the various sources available through the
|
|
CPU's own multiplexor, and those on off-CPU peripherals.
|
|
|
|
|
|
(*) Accessing PCI Devices
|
|
|
|
Where PCI is available, care must be taken when dealing with drivers that
|
|
access PCI devices. PCI devices present their data in little-endian form,
|
|
but the CPU sees it in big-endian form. The macros in asm/io.h try to get
|
|
this right, but may not under all circumstances...
|
|
|
|
|
|
(*) Ax88796 Ethernet Driver
|
|
|
|
The MB93093 PDK board has an Ax88796 ethernet chipset (an NE2000 clone). A
|
|
driver has been written to deal specifically with this. The driver
|
|
provides MII services for the card.
|
|
|
|
The driver can be configured by running make xconfig, and going to:
|
|
|
|
(*) Network device support
|
|
- turn on "Network device support"
|
|
(*) Ethernet (10 or 100Mbit)
|
|
- turn on "Ethernet (10 or 100Mbit)"
|
|
- turn on "AX88796 NE2000 compatible chipset"
|
|
|
|
The driver can be found in:
|
|
|
|
drivers/net/ax88796.c
|
|
include/asm/ax88796.h
|
|
|
|
|
|
(*) WorkRAM Driver
|
|
|
|
This driver provides a character device that permits access to the WorkRAM
|
|
that can be found on the FR451 CPU. Each page is accessible through a
|
|
separate minor number, thereby permitting each page to have its own
|
|
filesystem permissions set on the device file.
|
|
|
|
The device files should be:
|
|
|
|
mknod /dev/frv/workram0 c 240 0
|
|
mknod /dev/frv/workram1 c 240 1
|
|
mknod /dev/frv/workram2 c 240 2
|
|
...
|
|
|
|
The driver will not permit the opening of any device file that does not
|
|
correspond to at least a partial page of WorkRAM. So the first device file
|
|
is the only one available on the FR451. If any other CPU is detected, none
|
|
of the devices will be openable.
|
|
|
|
The devices can be accessed with read, write and llseek, and can also be
|
|
mmapped. If they're mmapped, they will only map at the appropriate
|
|
0x7e8nnnnn address on linux and at the 0xfe8nnnnn address on uClinux. If
|
|
MAP_FIXED is not specified, the appropriate address will be chosen anyway.
|
|
|
|
The mappings must be MAP_SHARED not MAP_PRIVATE, and must not be
|
|
PROT_EXEC. They must also start at file offset 0, and must not be longer
|
|
than one page in size.
|
|
|
|
This driver can be configured by running make xconfig, and going to:
|
|
|
|
(*) Character devices
|
|
- turn on "Fujitsu FR-V CPU WorkRAM support"
|
|
|
|
|
|
(*) Dynamic data cache write mode changing
|
|
|
|
It is possible to view and to change the data cache's write mode through
|
|
the /proc/sys/frv/cache-mode file while the kernel is running. There are
|
|
two modes available:
|
|
|
|
NAME MEANING
|
|
===== ==========================================
|
|
wthru Data cache is in Write-Through mode
|
|
wback Data cache is in Write-Back/Copy-Back mode
|
|
|
|
To read the cache mode:
|
|
|
|
# cat /proc/sys/frv/cache-mode
|
|
wthru
|
|
|
|
To change the cache mode:
|
|
|
|
# echo wback >/proc/sys/frv/cache-mode
|
|
# cat /proc/sys/frv/cache-mode
|
|
wback
|
|
|
|
|
|
(*) MMU Context IDs and Pinning
|
|
|
|
On MMU Linux the CPU supports the concept of a context ID in its MMU to
|
|
make it more efficient (TLB entries are labelled with a context ID to link
|
|
them to specific tasks).
|
|
|
|
Normally once a context ID is allocated, it will remain affixed to a task
|
|
or CLONE_VM'd group of tasks for as long as it exists. However, since the
|
|
kernel is capable of supporting more tasks than there are possible ID
|
|
numbers, the kernel will pass context IDs from one task to another if
|
|
there are insufficient available.
|
|
|
|
The context ID currently in use by a task can be viewed in /proc:
|
|
|
|
# grep CXNR /proc/1/status
|
|
CXNR: 1
|
|
|
|
Note that kernel threads do not have a userspace context, and so will not
|
|
show a CXNR entry in that file.
|
|
|
|
Under some circumstances, however, it is desirable to pin a context ID on
|
|
a process such that the kernel won't pass it on. This can be done by
|
|
writing the process ID of the target process to a special file:
|
|
|
|
# echo 17 >/proc/sys/frv/pin-cxnr
|
|
|
|
Reading from the file will then show the context ID pinned.
|
|
|
|
# cat /proc/sys/frv/pin-cxnr
|
|
4
|
|
|
|
The context ID will remain pinned as long as any process is using that
|
|
context, i.e.: when the all the subscribing processes have exited or
|
|
exec'd; or when an unpinning request happens:
|
|
|
|
# echo 0 >/proc/sys/frv/pin-cxnr
|
|
|
|
When there isn't a pinned context, the file shows -1:
|
|
|
|
# cat /proc/sys/frv/pin-cxnr
|
|
-1
|