[linux-cirrus] Memory mapping (virtual to physical) __virt_to_phys()
- From: "Wagner Scott (ST-IN/ENG1.1)" <Scott.Wagner@xxxxxxxxxxxx>
- To: <linux-cirrus@xxxxxxxxxxxxx>
- Date: Mon, 18 Jun 2007 09:08:54 -0400
Hello all,
I have an EP9302 running Linux 2.6.14 and using the following memory
mapping:
* 0xF200_0000 - 0xF2FF_FFFF 16 MB 0xfebfc000 nCS0 NAND
Flash Address
* 0xF100_0000 - 0xF1FF_FFFF 16 MB 0xfebfb000 nCS0 NAND
Flash Command
* 0xF000_0000 - 0xF0FF_FFFF 16 MB 0xfebfa000 nCS0 NAND
Flash Data
* 0xE000_0000 - 0xEFFF_FFFF 256 MB 0xc8000000 nSDCS2 SDRAM #2
* 0xD000_0000 - 0xDFFF_FFFF 256 MB - nSDCS1 Unused
* 0xC000_0000 - 0xCFFF_FFFF 256 MB - nSDCS0 Unused
* 0x8080_0000 - 0x8FFF_FFFF 248 MB 0xE0800000 APB EP9302
Peripherals
* 0x8000_0000 - 0x800F_FFFF 1 MB 0xE0000000 AHB EP9302
Peripherals
* 0x7000_0000 - 0x7FFF_FFFF 256 MB - nCS7 Unused
* 0x6000_0000 - 0x6FFF_FFFF 256 MB - nCS6 Unused
* 0x4000_0000 - 0x4FFF_FFFF Unused
* 0x3000_0000 - 0x3000_00FF 256 B 0xfebf3000 nCS3
Peripheral 3
* 0x2000_0000 - 0x2000_00FF 256 B 0xfebf2000 nCS2
Peripheral 2
* 0x1000_0000 - 0x1000_00FF 256 B 0xfebf0000 nCS1
Peripheral 1
* 0x0000_0000 - 0x0FFF_FFFF 256 MB 0xc0000000 nSDCS3 SDRAM #1
My problem is with the __virt_to_phys() macro in
./include/arch/arm/memory.h. I have __phys_to_virt() mapping SDRAM
physical addresses 0x00nn_nnnn to vrtual 0xC0nn_nnnn for the low block;
0xE0nn_nnnn to 0xC8nn_nnnn for the low block. I would expect that
__virt_to_phys() should map addresses 0xC0nn_nnnn to 0x00nn_nnnn for the
low block; 0xC8nn_nnnn to 0xE0nn_nnnn for the low block.
This does not do what I expect. When I use this __virt_to_phys()
mapping, the EP9302 peripherals do not work (note that they are mapped
at virtual address 0xE0nn_nnnn). If I have __virt_to_phys() map the
high block at C800_0000 to 4000_0000 (where there is nothing in either
virtual or physical space), everything seems to work OK.
I don't understand this. First, why can't I do a V to P mapping back to
E0x? The peripherals are at _virtual_ E0, not _physical_ E0. Second,
why does lying and mapping the high SDRAM block back to 40x (where there
is absolutely nothing) work?
Thanks in advance.
Scott Wagner
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