Re: [PATCH 1/1] dma-contiguous: return early for dt case in dma_contiguous_reserve

[Robin Murphy]

On 2021-05-31 10:21, Dong Aisheng wrote:
> On Tue, May 18, 2021 at 7:29 PM Dong Aisheng <aisheng.dong@xxxxxxx> wrote:
> > dma_contiguous_reserve() aims to support cmdline case for CMA memory
> > reserve. But if users define reserved memory in DT,
> > 'dma_contiguous_default_area' will not be 0, then it's meaningless
> > to continue to run dma_contiguous_reserve(). So we return early
> > if detect 'dma_contiguous_default_area' is unzero.
> >
> > Cc: Christoph Hellwig <hch@xxxxxx>
> > Cc: Marek Szyprowski <m.szyprowski@xxxxxxxxxxx>
> > Cc: Robin Murphy <robin.murphy@xxxxxxx>
> > Signed-off-by: Dong Aisheng <aisheng.dong@xxxxxxx>
>
> Gently ping

The commit message is still wrong, and I still think the change doesn't 
achieve anything meaningful. This code is hard to make sense of either 
way because the crucial interplay between size_cmdline and 
dma_contiguous_default_area is hidden somewhere else entirely, and it 
would take a much more significant refactoring to clear that up.

Robin.

> Regards
> Aisheng
>
> > ---
> >   kernel/dma/contiguous.c | 5 ++++-
> >   1 file changed, 4 insertions(+), 1 deletion(-)
> >
> > diff --git a/kernel/dma/contiguous.c b/kernel/dma/contiguous.c
> > index 3d63d91cba5c..ebade9f43eff 100644
> > --- a/kernel/dma/contiguous.c
> > +++ b/kernel/dma/contiguous.c
> > @@ -171,6 +171,9 @@ void __init dma_contiguous_reserve(phys_addr_t limit)
> >          phys_addr_t selected_limit = limit;
> >          bool fixed = false;
> >
> > +       if (dma_contiguous_default_area)
> > +               return;
> > +
> >          pr_debug("%s(limit %08lx)\n", __func__, (unsigned long)limit);
> >
> >          if (size_cmdline != -1) {
> > @@ -191,7 +194,7 @@ void __init dma_contiguous_reserve(phys_addr_t limit)
> >   #endif
> >          }
> >
> > -       if (selected_size && !dma_contiguous_default_area) {
> > +       if (selected_size) {
> >                  pr_debug("%s: reserving %ld MiB for global area\n", __func__,
> >                           (unsigned long)selected_size / SZ_1M);
> >
> > --
> > 2.25.1