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SubjectRe: n900 in next-20170901
On Fri, Nov 10, 2017 at 07:36:20AM -0800, Tony Lindgren wrote:
> * Joonsoo Kim <iamjoonsoo.kim@lge.com> [171110 06:34]:
> > On Thu, Nov 09, 2017 at 07:26:10PM -0800, Tony Lindgren wrote:
> > > +#define OMAP34XX_SRAM_PHYS 0x40200000
> > > +#define OMAP34XX_SRAM_VIRT 0xd0010000
> > > +#define OMAP34XX_SRAM_SIZE 0x10000
> >
> > For my testing environment, vmalloc address space is started at
> > roughly 0xe0000000 so 0xd0010000 would not be valid.
>
> Well we can map it anywhere we want, got any preferences?

My testing environment is a beagle-(xm?) for QEMU. It is configured by
CONFIG_VMSPLIT_3G=y so kernel address space is started at 0xc0000000.
And, it has 512 MB memory so 0xc0000000 ~ 0xdff00000 is used for
direct mapping. See below.

[ 0.000000] Memory: 429504K/522240K available (11264K kernel code,
1562K rwdata, 4288K rodata, 2048K init, 405K bss, 27200K reserved,
65536K cma-reserved, 0K highmem)
[ 0.000000] Virtual kernel memory layout:
[ 0.000000] vector : 0xffff0000 - 0xffff1000 ( 4 kB)
[ 0.000000] fixmap : 0xffc00000 - 0xfff00000 (3072 kB)
[ 0.000000] vmalloc : 0xe0000000 - 0xff800000 ( 504 MB)
[ 0.000000] lowmem : 0xc0000000 - 0xdff00000 ( 511 MB)
[ 0.000000] pkmap : 0xbfe00000 - 0xc0000000 ( 2 MB)
[ 0.000000] modules : 0xbf000000 - 0xbfe00000 ( 14 MB)
[ 0.000000] .text : 0xc0208000 - 0xc0e00000 (12256 kB)
[ 0.000000] .init : 0xc1300000 - 0xc1500000 (2048 kB)
[ 0.000000] .data : 0xc1500000 - 0xc1686810 (1563 kB)
[ 0.000000] .bss : 0xc168fc68 - 0xc16f512c ( 406 kB)

Therefore, if OMAP34XX_SRAM_VIRT is 0xd0010000, direct mapping is
broken and the system doesn't work. I guess that we should use more
stable address like as 0xf0000000.

>
> Just that the current save_secure_ram_context uses "high_mask"
> of 0xffff to translate the address. To make this more flexible,
> we need the save_secure_ram_context changes too. So we might
> want to do the static mapping and save_secure_ram_context changes
> as a single patch.
>
> > And, PHYS can be different according to the system type. Maybe either
> > OMAP3_SRAM_PUB_PA or OMAP3_SRAM_PA. It seems that SIZE and TYPE should
> > be considered, too. My understanding is correct?
>
> We can have a static map for the whole SRAM area, see function
> __arm_ioremap_pfn_caller() for the comment "Try to reuse one of the
> static mapping whenever possible". So the different public SRAM start
> addresses and sizes don't matter there.

Okay. Look fine with SRAM start addresses and sizes. However, we need
to consider mtype since __arm_ioremap_pfn_caller() doesn't reuse the
mapping if mtype is different. mtype can be either MT_MEMORY_RWX or
MT_MEMORY_RWX_NONCACHED.

Thanks.

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