Accessing physical memory on ARM

[Adit Sahasrabudhe]

There is some documentation for this online:

https://docs.rtems.org/doxygen/cpukit/html/group__ClassicCache.html


On 11/11/15, 10:54 PM, "users on behalf of Sebastian Huber"
<users-bounces at rtems.org on behalf of sebastian.huber at embedded-brains.de>
wrote:

>
>
>On 12/11/15 07:39, Chris Johns wrote:
>> On 12/11/2015 5:26 PM, Sebastian Huber wrote:
>>>
>>> On 11/11/15 23:32, Adit Sahasrabudhe wrote:
>>>> It turns out it¹s a cache issue. Our application has the FPGA on the
>>>> SoC writing data to the SDRAM. We ran another test where we made sure
>>>> the test buffer would create a cache miss and sure enough, the data is
>>>> read just fine.
>>>>
>>>> So one last question then, since this data is only written by the
>>>> FPGA, it seems like I have two options:
>>>>
>>>>   1. Create a new section in my linker script and configure the MMU
>>>>for
>>>>      that section to not use cache (using startup/mmu_config.c in the
>>>>BSP)
>>>>
>>> You can use rtems_cache_coherent_allocate() or place global data into
>>> non-cacheable memory via the BSP_NOCACHE_SECTION and
>>> BSP_NOCACHENOLOAD_SECTION attributes (#include <bsp/linker-symbols.h>).
>>>
>> Thanks Sebastian.
>>
>> Is there a documentation link describing this?
>
>No, we don't have BSP documentation.
>
>>
>>>>   1. Or, I can invalidate the cache whenever we want to read this
>>>>      buffer (not too often). Is there an API available to do cache
>>>>      invalidations? We tried the inline routines in arm-cp15.h, but it
>>>>      causes a fatal exception.
>>>>
>>> Use the rtems_cache_*() routines for this.
>>>
>> A documentation link?
>
>The cache manager is not documented in the user manual.
>
>-- 
>Sebastian Huber, embedded brains GmbH
>
>Address : Dornierstr. 4, D-82178 Puchheim, Germany
>Phone   : +49 89 189 47 41-16
>Fax     : +49 89 189 47 41-09
>E-Mail  : sebastian.huber at embedded-brains.de
>PGP     : Public key available on request.
>
>Diese Nachricht ist keine geschäftliche Mitteilung im Sinne des EHUG.
>
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