I am trying to get an external ide-pci controller (CMD 646) working on an
embedded mips board. The kernel-source is based on a 2.2.12 source tree.
The problem is doing DMA. I receive address (0x80ff0000) for my dmatable in
the function ide_setup_dma (__get_free_pages). Then in ide_buildtable it
sets up the dmatable. Address 0x80376000 and a count of 0x400
(check_partition reads 2 sectors from the harddrive). These are all virtual
addresses. For setting up the dmatable I use physical addresses. On the
embedded board there is a 1:1 map of i/o bus to main memory so
platform_mem_iobus_base is 0.
So after doing the DMA read, I read only zero's at address 0x80376000 and
the kernel hangs. But the harddrive is ready and I can't find any errors. It
seems that it writes the data to a different memory location. After
searching the memory the data is written at address 0x80000000?? Is the
memory manager somewhere in between???
The next thing I did was reserving a piece of physical memory for DMA and
fill in the dmatable myself. So that it uses my piece of reserved memory.
After I did this, the data was at the correct address and the kernel didn't
crash. Is this the solution???
Anyone a clue?
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