Wonderful. I liked it. Please see inline On Tue, Jul 10, 2012 at 7:37 PM, 弋天 卜 <[email protected]> wrote:
> > > 在 2012-7-10，12:58，Prabhu nath < <[email protected]> > [email protected]> 写道： > > Dear All, > > Is it possible to map a physical address of a device to > a known Kernel virtual address. I know about ioremap_xxx (...). > which will map a physical address of a device to a kernel virtual address > allocated by ioremap_xxx(...). > > For E.g. I have a device whose physical address range is 0x80008000 to > 0x80008FFF. > Is it possible to map this device physical address to a known > virtual address range 0xF0008000 to 0xF0008FFF. > > > you can do this if you know exactly what you are doing, please follow > below steps: > 1. ask yourself why you need this fix map to a device io address? if you > only want to get a fix formula to calculate > device virutal address from physical address, you can call ioremap(), and > store the return value into a global variable. > > 2. ask the architecturer of you platform provider, or you search into > source code by yourself, make sure > whether the virtual address range 0xF0008000 to 0xF0008FFF has not been > mapped yet, this is very important because > kernel region cannot be mapped twice. othersie you will get warning from > log and without remap this region finally. > > 3. suppose step 2 is ok, the region is not mapped, then call function > ioremap_page_range(0xF0008000, 0xF0009000, 0x80008000, pgprot); > kernel will map virtual address [0xF0008000~0xF0009000] to physical > address [0x80008000~0x80009000] . > > Note! you must make sure this region has not been mapped before on > your platform. as i guess, they are 99% mapped already :=) > > > > My hardware configuration has 128 MB of system RAM which will have been > MAPPED to the Kernel virtual address from 0xC0000000 to 0xC7FFFFFF > > Also is it possible to configure the vmalloc kernel virtual address region > to a fixed range of 128 MB from 0xC8000000 to 0xCFFFFFFF > > you can try to do it as below: > 1. find the definition of VMALLOC_END, define it to be 0xD0800000, the > original value will be something like 0xF0000000: > #define VMALLOC_END 0xD0800000 > > 2. pass in parameter from u-boot to kernel, set "vmalloc=128M" > > 3. now you should get result from boot log as below: > [ 0.000000] vmalloc : 0xc8800000 - 0xd0800000 ( 128 MB) > [ 0.000000] lowmem : 0xc0000000 - 0xc8000000 ( 128 MB) > 4. although you did what you want to do, i am sure that you don't know > what you really want to do because these steps make no sense. > keep in mind that vmalloc region, which is from VMALLOC_START to > VMALLOC_END, does not use direct memory map. > Very humbly I should confess that I know what I am doing. I want a clear demarkation betwen vmalloc region and kernel virtual address of the physical devices, so that it will help me in future debugging. > > > > Thanks, > Prabhu > > _______________________________________________ > Kernelnewbies mailing list > <[email protected]>[email protected] > <http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies> > http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies > >
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