PowerPC equivalent to dma_mmap_writecombine()?
I'm porting a driver from ARM to PowerPC, and I came across this function:
static int at91_pcm_mmap(struct snd_pcm_substream *substream,
struct vm_area_struct *vma)
{
struct snd_pcm_runtime *runtime = substream->runtime;
return dma_mmap_writecombine(substream->pcm->card->dev, vma,
runtime->dma_area,
runtime->dma_addr,
runtime->dma_bytes);
}There are no dma_mmap_x() functions in arch/powerpc. Can someone tell me what the powerpc equivalent to dma_mmap_writecombine() is?
Signature · 2 lines
Timur Tabi Linux Kernel Developer @ Freescale
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Quoted 6 lines
Quoted 2 lines
There are no
dma_mmap_x()functions inarch/powerpc. Can someone tell me what the powerpc equivalent todma_mmap_writecombine()is?Not sure exactly what arm does here, but it sounds like you want to call
remap_pfn_rangewith the_PAGE_NO_CACHEbit set in the protection flags, and_PAGE_GUARDEDnot set.
Either that, or just map it as normal cache-coherent DMA memory.
Segher
Quoted 3 lines · Arnd Bergmann
Not sure exactly what arm does here, but it sounds like you want to call
remap_pfn_rangewith the_PAGE_NO_CACHEbit set in the protection flags, and_PAGE_GUARDEDnot set.
I always have a hard time with these mapping functions. Is this right?
vma->vm_page_prot = __pgprot((pgprot_val(vma->vm_page_prot) | _PAGE_NO_CACHE) & ~_PAGE_GUARDED));
ret = remap_pfn_range(vma, vma->vm_start, runtime->dma_addr, runtime->dma_bytes, vma->vm_page_prot);
Alternatively, could I use function snd_pcm_lib_mmap_iomem() (sound/core/pcm_native.c)? It looks like it does the right thing, although it doesn't unset the guarded bit. If that's wrong, I can submit a patch to unset that bit on PowerPC, but like I said, I can never quite get my head around this mapping stuff.
Signature · 2 lines
Timur Tabi Linux Kernel Developer @ Freescale
Quoted 9 lines · Timur Tabi
Arnd Bergmann wrote:
=20Quoted 3 lines
Not sure exactly what arm does here, but it sounds like you want to call
remap_pfn_rangewith the_PAGE_NO_CACHEbit set in the protection flags, and_PAGE_GUARDEDnot set.=20
I always have a hard time with these mapping functions. =A0Is this right? =20vma->vm_page_prot=3D __pgprot((pgprot_val(vma->vm_page_prot) | _PAGE_NO_=
CACHE) &=20
Quoted 3 lines
~_PAGE_GUARDED));
=20
ret =3D remap_pfn_range(vma,vma->vm_start,runtime->dma_addr, runtime->d=
ma_bytes,=20
Quoted 3 lines
vma->vm_page_prot);
=20
Alternatively, could I use functionsnd_pcm_lib_mmap_iomem()(sound/core/=
pcm_native.c)?=20
Quoted 1 line
It looks like it does the right thing, although it doesn't unset the guar=
ded bit. =A0If=20
Quoted 1 line
that's wrong, I can submit a patch to unset that bit on PowerPC, but like=
I said, I can=20
Quoted 1 line
never quite get my head around this mapping stuff.
The guarded bit is disabled by default, so you don't need t remove it, so the function you quoted should be alright for this purpose. Not sure if you need the ioremap in there though.
Arnd <><