[PATCH V2 4/4] POWERPC: Merge 32 and 64-bit dma code

[Kumar Gala]

On Oct 13, 2008, at 10:41 AM, Josh Boyer wrote:

> On Mon, Oct 13, 2008 at 10:49:04AM -0400, Josh Boyer wrote:
>> On Fri, Sep 12, 2008 at 03:34:46PM -0500, Becky Bruce wrote:
>>> We essentially adopt the 64-bit dma code, with some changes to  
>>> support
>>> 32-bit systems, including HIGHMEM.  dma functions on 32-bit are now
>>> invoked via accessor functions which call the correct op for a  
>>> device based
>>> on archdata dma_ops.  If there is no archdata dma_ops, this defaults
>>> to dma_direct_ops.
>>>
>>> In addition, the dma_map/unmap_page functions are added to dma_ops
>>> because we can't just fall back on map/unmap_single when HIGHMEM is
>>> enabled. In the case of dma_direct_*, we stop using map/unmap_single
>>> and just use the page version - this saves a lot of ugly
>>> ifdeffing.  We leave map/unmap_single in the dma_ops definition,
>>> though, because they are needed by the iommu code, which does not
>>> implement map/unmap_page.  Ideally, going forward, we will  
>>> completely
>>> eliminate map/unmap_single and just have map/unmap_page, if it's
>>> workable for 64-bit.
>>>
>>> Signed-off-by: Becky Bruce <becky.bruce at freescale.com>
>>
>> While doing a buildall this morning, I notice chrp32_defconfig fails
>> to build with:
>>
>> drivers/built-in.o: In function `hard_dma_setup':
>> floppy.c:(.text+0x6e40e): undefined reference to `isa_bridge_pcidev'
>> floppy.c:(.text+0x6e412): undefined reference to `isa_bridge_pcidev'
>> floppy.c:(.text+0x6e53e): undefined reference to `isa_bridge_pcidev'
>> floppy.c:(.text+0x6e546): undefined reference to `isa_bridge_pcidev'
>> floppy.c:(.text+0x6e54a): undefined reference to `isa_bridge_pcidev'
>> make[1]: *** [.tmp_vmlinux1] Error 1
>>
>> (the hard_dma_setup thing is in arch/powerpc/include/asm/floppy.h).
>>
>> I did a git bisect and it pointed at this commit as causing the build
>> to fail.  Why, I have no idea.
>
> Ok, I was annoyed enough to look at why.
>
> Basically, before this patch pci_map_single on 32-bit PPC seemed to
> be compiled down to __dma_sync(ptr, size, direction); and the "dev"
> parameter to the function was never actually used.  The compiler
> seems to have optimized this out entirely, so we don't get the odd
> link reference to isa_bridge_pcidev at all.  (Neither pci_map_single
> or isa_bridge_pcidev are present in the vmlinux at all).
>
> With the patch, the compiler doesn't do this code elimination
> because pci_map_single boils down to dma_map_page, which calls
> get_dma_direct_offset with the "dev" parameter.  So since it is
> still used, the compiler can't eliminate it and hence FAIL.
>
> I have no patch for this at the moment.  Someone should look at
> it more closely, because this is causing the 5 chrp32_defconfig
> users to weep.

Isn't this the type of regression we should fix post -rc1 :)

- k