Messages in this thread | | | Subject | Re: non volatile ram disk | From | Erez Doron <> | Date | 22 Jan 2002 11:39:50 +0200 |
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On Mon, 2002-01-21 at 17:21, Peter Wächtler wrote: > Erez Doron schrieb: > > > > the exact log i get: > > > > Creating 3 MTD partitions on "SA1100 flash": > > 0x00000000-0x00040000 : "bootldr" > > mtd: Giving out device 0 to bootldr > > 0x00040000-0x02000000 : "root" > > mtd: Giving out device 1 to root > > 0xc2000000-0xc4000000 : "rd" > > mtd: partition "rd" is out of reach -- disabled > > > > notes: > > 1. the flash is at physical adress 0-0x1ffffff (32mb) > > 2. the ram is at physical adress 0xc0000000-0xc3ffffff > > i tried to map an mtd device to the second part of the ram, but got > > "partition is out of reach" > > > > any idea ? > > you are confusing the address space of the kernel (starting with 3GB [0xc0000000]) > with the addresses of the RAM (the upper 32MB starts at 0x2000000) > no, i do not ( compaq document says the ram starts at 0xc0000000, i also verified it by doing peek and poke via the bootloader)
> Then there will be some CS (chip selects) to distinguish what "bus address space" > to use. Like CS1 for Flash and CS0 for RAM (don't know details of SA1100/iPAQ) > > You have to use the special MTD device that talks to system RAM. > Again, I don't know the details, but menuconfig gives you: > > RAM/ROM/Flash chip drivers > Support for RAM chips in bus mapping > > Self-contained MTD device drivers > Uncached system RAM (NEW) > > The former sounds like RAM on expansion bus, the latter seems to be > what you are looking for. > > Now: is the RAM battery backed, or not? If not, you want to use > the flash as nonvolatile disk - otherwise there would be no need > to restart the system and hence a normal RAM disk would be nonvolatile. > yes it is
thanks anyway erez. > > > > > On Mon, 2002-01-21 at 15:42, Erez Doron wrote: > > > hi > > > > > > thanks for replying, > > > > > > I already tried to map an MTD to physical memory, but got an error and > > > an mtd with size 0 > > > > > > dou you know why ? > > > > > > regards > > > erez > > > > > > On Mon, 2002-01-21 at 15:41, Peter Wächtler wrote: > > > > Erez Doron schrieb: > > > > > > > > > > hi > > > > > > > > > > I'm looking for a way to make a ramdisk which is not erased on reboot > > > > > this is for use with ipaq/linux. > > > > > > > > > > i tought of booting with mem=32m and map a block device to the rest of > > > > > the 32M ram i have. > > > > > > > > > > the probelm is that giving mem=32m to the kernel will cause the kernel > > > > > to map only the first 32m of physical memory to virtual one, so using > > > > > __pa(ptr) on the top 32m causes a kernel oops. > > > > > > > > > > any idea ? > > > > > > > > > > > > > a MTD is the way to go, which uses the "reserved" mem area. > > > > I assume that the RAM is battery backed > > > > -
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