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Diffstat (limited to 'Documentation/frv/features.txt')
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diff --git a/Documentation/frv/features.txt b/Documentation/frv/features.txt deleted file mode 100644 index fa20c0e72833..000000000000 --- a/Documentation/frv/features.txt +++ /dev/null @@ -1,310 +0,0 @@ - =========================== - 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 |