Saroj Kumar Mohapatra a écrit :
I'm trying to run ioremap on the memory location I reserved from the lilo command, that is to say , the memory above 40M.
On 5/23/05, *nicolas Wilczak* <wilczak@xxxxxxxxx <mailto:wilczak@xxxxxxxxx>> wrote:
>>Using LILO and the mem=40M to allow 40M for the system, and I would like >>to access the memory after. >>I've read that I have to do : ioremap(0x2800000/*40M*/, ... but I'm not >>sure I access to the good memory region. >> >> > >Yes, you can now access the RAM above 40MB with ioremap ..... what do >you mean by good memory regoin ? > > > The thing I realy does understand it's: - when I get 1 page from get_free_page , and I give the address to the device ( for a PCI device driver ) : page = alloc_page(GFP_KERNEL); pci_write_config_dword(dev,0xa8, virt_to_bus(page_address(page))); It works, I can access the this space from pci device.
- when I do : buf = ioremap(0x2800000,0x100000);
on waht address you are trying to run ioremap.
its meant for PCI device address space. and not below that. memory below that is the point where it gets remaped
And I want use it as shared memory for a pci device....
pci_write_config_dword(dev,0xa8, virt_to_bus(buf)); It doesn't work .... So do I have to use some function like io_remap_page_range or something else. I don't well understant why I can access this memory space from the device?
>>Does somebody know the good method to reserve large memory region ? >>I'm using 2.6 kernel. >> >> > >As you already reserved the RAM above 40MB through mem=40M option, now >you can use it freely through ioremap and you can consider this region >as usable regoing for you ...... You have to use ioremap to map memory >in chunks, map a chunk of memory let say 4KB (a page) use it, unmap it >and then map other 4KB and so on ....... then you can access whole >memory above 40M or your reserved memory. > > >
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