[linux-cirrus] Re: Memory mapping (virtual to physical) __virt_to_phys()
- From: "Stuart Wood" <stuart.wood@xxxxxxxxxxxxxxxxxxxx>
- To: <linux-cirrus@xxxxxxxxxxxxx>
- Date: Mon, 18 Jun 2007 10:25:51 -0400
Hey Scott,
So, Why do you want to force the virtual address for the peripherals to
E0x?, from the febfxxxx that TS set up? On the other hand you can just let
the kernel dynamically set up the virtual address like I'm doing. The only
gotcha there is that I'm having trouble with disabling cached reads outside
of the driver when using mmap.
Stuart Wood
-----Original Message-----
From: linux-cirrus-bounce@xxxxxxxxxxxxx
[mailto:linux-cirrus-bounce@xxxxxxxxxxxxx] On Behalf Of Wagner Scott
(ST-IN/ENG1.1)
Sent: Monday, June 18, 2007 9:09 AM
To: linux-cirrus@xxxxxxxxxxxxx
Subject: [linux-cirrus] Memory mapping (virtual to physical)
__virt_to_phys()
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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