Hemanth,
I might be missing something but please see below:
>
>
>Hemanth,
> Why do you want the split? Do you have physical mem > 1G
>in your system?
>
>We want to fit 512MB RAM on 2.6.27 Kernel which doesnot have highmem option.
>We also donot want to disturb the current I/O memory map
[Romit] As long as your physical memory is slightly less than 1GB, I do not think highmem is necessary.
For I/O map: Kernel virtual addresses start from 0xC0000000. Adding 512M to it gives 0xE0000000. So the virtual memory for IO space needs to be after this.
Currently the IO Map is
#define L4_WK_34XX_PHYS L4_WK_34XX_BASE /* 0x48300000 */
#define L4_WK_34XX_VIRT 0xd8300000
#define L4_WK_34XX_SIZE SZ_1M
#define L4_PER_34XX_VIRT 0xd9000000
#define L4_PER_34XX_SIZE SZ_1M
#define L4_EMU_34XX_VIRT 0xe4000000
#define L4_EMU_34XX_SIZE SZ_64M
#define OMAP34XX_GPMC_PHYS OMAP34XX_GPMC_BASE /* 0x6E000000 */
#define OMAP34XX_GPMC_VIRT 0xFE000000
#define OMAP34XX_GPMC_SIZE SZ_1M
#define OMAP343X_SMS_VIRT 0xFC000000
#define OMAP343X_SMS_SIZE SZ_1M
#define OMAP343X_SDRC_PHYS OMAP343X_SDRC_BASE /* 0x6D000000 */
#define OMAP343X_SDRC_VIRT 0xFD000000
#define OMAP343X_SDRC_SIZE SZ_1M
This is a problem as the existing virtual memory maps for I/O space would overlap with 512M SDRAM. So, we need to redefine the virtual mapping after 0xe0000000. The IO_OFFSET is 0x90000000 currently.
For L4_WK_34XX_VIRT we need a minimum of 0xe0000000 - 0x48300000 i.e. 0x97D00000 as the new IO_OFFSET. But using this new IO_OFFSET for mapping OMAP343x_GPMC_VIRT would result in an overflow(0x6E000000 + 0x97D00000 = 0x105D00000).
Using ioremap for these regions might help. But this needs changes to most drivers. In that case these static mappings could go away and I think they should. Some ARM kernel expert may comment!
-Romit
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