Re: [PATCH v2 04/10] DMA, CMA: support alignment constraint on cma region

Joonsoo Kim
2014-06-16T05:19:52Z

On Thu, Jun 12, 2014 at 12:02:38PM +0200, Michal Nazarewicz wrote:
> On Thu, Jun 12 2014, Joonsoo Kim <iamjoonsoo.kim@lge.com> wrote:
> > ppc kvm's cma area management needs alignment constraint on
>
> I've noticed it earlier and cannot seem to get to terms with this. It
> should IMO be PPC, KVM and CMA since those are acronyms. But if you
> have strong feelings, it's not a big issue.

Yes, I will fix it.

>
> > cma region. So support it to prepare generalization of cma area
> > management functionality.
> >
> > Additionally, add some comments which tell us why alignment
> > constraint is needed on cma region.
> >
> > Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@lge.com>
>
> Acked-by: Michal Nazarewicz <mina86@mina86.com>
>
> > diff --git a/drivers/base/dma-contiguous.c b/drivers/base/dma-contiguous.c
> > index 8a44c82..bc4c171 100644
> > --- a/drivers/base/dma-contiguous.c
> > +++ b/drivers/base/dma-contiguous.c
> > @@ -219,6 +220,7 @@ core_initcall(cma_init_reserved_areas);
> > * @size: Size of the reserved area (in bytes),
> > * @base: Base address of the reserved area optional, use 0 for any
> > * @limit: End address of the reserved memory (optional, 0 for any).
> > + * @alignment: Alignment for the contiguous memory area, should be
> > power of 2
>
> “must be power of 2 or zero”.

Okay.

> > * @res_cma: Pointer to store the created cma region.
> > * @fixed: hint about where to place the reserved area
> > *
> > @@ -233,15 +235,15 @@ core_initcall(cma_init_reserved_areas);
> > */
> > static int __init __dma_contiguous_reserve_area(phys_addr_t size,
> > phys_addr_t base, phys_addr_t limit,
> > + phys_addr_t alignment,
> > struct cma **res_cma, bool fixed)
> > {
> > struct cma *cma = &cma_areas[cma_area_count];
> > - phys_addr_t alignment;
> > int ret = 0;
> >
> > - pr_debug("%s(size %lx, base %08lx, limit %08lx)\n", __func__,
> > - (unsigned long)size, (unsigned long)base,
> > - (unsigned long)limit);
> > + pr_debug("%s(size %lx, base %08lx, limit %08lx align_order %08lx)\n",
> > + __func__, (unsigned long)size, (unsigned long)base,
> > + (unsigned long)limit, (unsigned long)alignment);
>
> Nit: Align with the rest of the arguments, i.e.:
>
> + pr_debug("%s(size %lx, base %08lx, limit %08lx align_order %08lx)\n",
> + __func__, (unsigned long)size, (unsigned long)base,
> + (unsigned long)limit, (unsigned long)alignment);

What's the difference between mine and yours?

Thanks.