Re: [P5600 && EVA memory caching question] PCI region

[Yuri Frolov <crashing.kernel@gmail.com>]

> I'm looking at arch/mips/include/asm//mach-malta/kernel-entry-init.h 
and there is a definition for
> SegCtl2:

>         /* SegCtl2 */
>         li      t0, ((MIPS_SEGCFG_MUSUK << MIPS_SEGCFG_AM_SHIFT) |      \
>                 (6 << MIPS_SEGCFG_PA_SHIFT) |                           \
>                 (1 << MIPS_SEGCFG_EU_SHIFT)) |                          \
>                 (((MIPS_SEGCFG_MUSUK << MIPS_SEGCFG_AM_SHIFT) |         \
>                 (4 << MIPS_SEGCFG_PA_SHIFT) |                           \
>                 (1 << MIPS_SEGCFG_EU_SHIFT)) << 16)
>
> it defines, that kernel logical addresses from the range 0x00000000 - 
> 0x7fffffff are unmapped (no tlbs) and dictates, that in order to get a 
> physical address for any logical addresses from 0x00000000 - 
> 0x3fffffff range in kernel space, bits [31:29] of the logical address 
> must be changed to 100,
> and (again in kernel space) for any logical addresses from 0x40000000 
> - 0x7fffffff range, bits [31:29] of the logical address must be 
> changed to 110, right?
> What physical addresses will logical addresses 0x00000000 and 
> 0x20000000 be translated in kernel space?.. logical 0x00000000 --> 
> physical 0x80000000, and logical 0x20000000 --> .... 0x80000000 too?
> Since we must to change bits [31:29], we have to change bit 29 ('1') 
> in logical address 0x200000000 to '0' (since PA for this range is 100).
> So, what physical addresses will all logical addresses which have '1' 
> at 29 bit be translated, if we define PA as 100 and 110 in SegCtl2? It 
> looks like there's no flat translation of logical addresses to 
> physical addresses in kernel space, and this is obviously just not 
> correct, there is something simple I've been overlooking.
> Thank you,
> Yuri
The only way this scheme can work, is that 'these bits are used' phrase 
from Table 3.5 CFG (Segment Configuration) Field Description means not 
'these bits substitute bits [31:29] in virtual address', but 'these bits 
are 'OR'-ed with bits [31:29] in virtual address.