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Eagerly map DMA buffers

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This patch is a work-around for issue #452.
This commit is contained in:
Norman Feske 2012-11-26 09:36:57 +01:00
parent f2e47ef9f4
commit 0bcf55800f
1 changed files with 18 additions and 0 deletions
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18
os/include/os/attached_ram_dataspace.h
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@ -22,6 +22,7 @@
#define _INCLUDE__OS__ATTACHED_RAM_DATASPACE_H_ #define _INCLUDE__OS__ATTACHED_RAM_DATASPACE_H_
#include <ram_session/ram_session.h> #include <ram_session/ram_session.h>
#include <util/touch.h>
#include <base/env.h> #include <base/env.h>
namespace Genode { namespace Genode {
@ -61,6 +62,23 @@ namespace Genode {
_ram_session->free(_ds); _ram_session->free(_ds);
throw; throw;
} }
/*
* Eagerly map dataspace if used for DMA
*
* On some platforms, namely Fiasco.OC on ARMv7, the handling
* of page faults interferes with the caching attributes used
* for uncached DMA memory. See issue #452 for more details
* (https://github.com/genodelabs/genode/issues/452). As a
* work-around for this issues, we eagerly map the whole
* dataspace before writing actual content to it.
*/
if (!_cached) {
enum { PAGE_SIZE = 4096 };
unsigned char volatile *base = (unsigned char volatile *)_local_addr;
for (size_t i = 0; i < _size; i += PAGE_SIZE)
touch_read_write(base + i);
}
} }
public: public: