/* * Copyright (c) 2000, 2001, 2002, 2003, 2004, 2005, 2008, 2009 * The President and Fellows of Harvard College. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * 1. Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * 2. Redistributions in binary form must reproduce the above copyright * notice, this list of conditions and the following disclaimer in the * documentation and/or other materials provided with the distribution. * 3. Neither the name of the University nor the names of its contributors * may be used to endorse or promote products derived from this software * without specific prior written permission. * * THIS SOFTWARE IS PROVIDED BY THE UNIVERSITY AND CONTRIBUTORS ``AS IS'' AND * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE * ARE DISCLAIMED. IN NO EVENT SHALL THE UNIVERSITY OR CONTRIBUTORS BE LIABLE * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF * SUCH DAMAGE. */ #include <types.h> #include <lib.h> #include <vm.h> #include <mainbus.h> vaddr_t firstfree; /* first free virtual address; set by start.S */ static paddr_t firstpaddr; /* address of first free physical page */ static paddr_t lastpaddr; /* one past end of last free physical page */ /* * Called very early in system boot to figure out how much physical * RAM is available. */ void ram_bootstrap(void) { size_t ramsize; /* Get size of RAM. */ ramsize = mainbus_ramsize(); /* * This is the same as the last physical address, as long as * we have less than 512 megabytes of memory. If we had more, * we wouldn't be able to access it all through kseg0 and * everything would get a lot more complicated. This is not a * case we are going to worry about. */ if (ramsize > 512*1024*1024) { ramsize = 512*1024*1024; } lastpaddr = ramsize; /* * Get first free virtual address from where start.S saved it. * Convert to physical address. */ firstpaddr = firstfree - MIPS_KSEG0; kprintf("%uk physical memory available\n", (lastpaddr-firstpaddr)/1024); } /* * This function is for allocating physical memory prior to VM * initialization. * * The pages it hands back will not be reported to the VM system when * the VM system calls ram_getsize(). If it's desired to free up these * pages later on after bootup is complete, some mechanism for adding * them to the VM system's page management must be implemented. * Alternatively, one can do enough VM initialization early so that * this function is never needed. * * Note: while the error return value of 0 is a legal physical address, * it's not a legal *allocatable* physical address, because it's the * page with the exception handlers on it. * * This function should not be called once the VM system is initialized, * so it is not synchronized. */ paddr_t ram_stealmem(unsigned long npages) { size_t size; paddr_t paddr; size = npages * PAGE_SIZE; if (firstpaddr + size > lastpaddr) { return 0; } paddr = firstpaddr; firstpaddr += size; return paddr; } /* * This function is intended to be called by the VM system when it * initializes in order to find out what memory it has available to * manage. Physical memory begins at physical address 0 and ends with * the address returned by this function. We assume that physical * memory is contiguous. This is not universally true, but is true on * the MIPS platforms we intend to run on. * * lastpaddr is constant once set by ram_bootstrap(), so this function * need not be synchronized. * * It is recommended, however, that this function be used only to * initialize the VM system, after which the VM system should take * charge of knowing what memory exists. */ paddr_t ram_getsize(void) { return lastpaddr; } /* * This function is intended to be called by the VM system when it * initializes in order to find out what memory it has available to * manage. * * It can only be called once, and once called ram_stealmem() will * no longer work, as that would invalidate the result it returned * and lead to multiple things using the same memory. * * This function should not be called once the VM system is initialized, * so it is not synchronized. */ paddr_t ram_getfirstfree(void) { paddr_t ret; ret = firstpaddr; firstpaddr = lastpaddr = 0; return ret; }