ioremap to a specific virtual address

[jonsmirl at gmail.com]

On Fri, Mar 23, 2012 at 12:00 AM, Nicolas Pitre <nico at fluxnic.net> wrote:
> On Thu, 22 Mar 2012, jonsmirl at gmail.com wrote:
>
>> When iotable is used to initially map memory you can specify the
>> mapping address. In this case IO_SDMMC_PHYS is 0x18000000 and it gets
>> mapped to  0xf1800000
>>
>> NXP has supplied this handly macro
>> #define io_p2v(x) (0xf0000000 | (((x) & 0xff000000) >> 4) | ((x) & 0x000fffff))
>>
>> iotable_init(lpc313x_io_desc, ARRAY_SIZE(lpc313x_io_desc));
>>
>>       {
>>               .virtual        = io_p2v(IO_SDMMC_PHYS),
>>               .pfn            = __phys_to_pfn(IO_SDMMC_PHYS),
>>               .length         = IO_SDMMC_SIZE,
>>               .type           = MT_DEVICE
>>       },
>>
>> The supplied kernel is full of code that uses this type of addressing.
>> It has macros for register definition that all depend on the registers
>> being mapped to a well know location - io_p2v(x).
>>
>> I'd like to move the map out of the core code and into the SDMMC
>> device driver and then only do it if the driver loads.
>
> Why would you do that?  Those static mappings are meant to be global and
> remain there.  The handy macro is in fact not handy at all as it forces
> virtual addresses on you.
>
> It is OK to keep the static mappings as you can use 1MB regions and the
> mapping code will use first level mappings which are better with TLB
> usage.

I switched over to 1MB mappings. 1MB map regions are implemented on
ARM9, right? Is there some way to see if I got the huge maps?

-- 
Jon Smirl
jonsmirl at gmail.com