[U-Boot] [PATCH] fdt_support: Use VLA instead of MEMORY_BANKS_MAX

[Ramon Fried]

On Mon, Aug 13, 2018 at 5:52 PM Tom Rini <trini at konsulko.com> wrote:

> On Mon, Aug 13, 2018 at 08:20:03AM +0100, Peter Robinson wrote:
>
> > On Sun, Aug 12, 2018 at 9:37 PM, Ramon Fried <ramon.fried at gmail.com>
> wrote:
> > > From: Ramon Fried <ramon.fried at intel.com>
> > >
> > > Instead of relaying on user to configure MEMORY_BANKS_MAX
> > > correctly, use VLA (variable length array) to accommodate the
> > > required banks.
> >
> > With the kernel actively removing VLAs [1] does it make sense for us
> > to use them?
>
> Agreed.
>
> Also, why is the answer NOT to go back to the way things were with
> 5e5745465c94 and increase CONFIG_NR_DRAM_BANKS when needed?  It seems
>
The whole purpose of my patch was to enable to fixup more banks than
defined in
CONFIG_NR_DRAM_BANKS.

Another option would be to add
+#ifndef MEMORY_BANKS_MAX
#define MEMORY_BANKS_MAX 4
+#endif
and let the use alter the value in include/configs if necessary.

Thanks,
Ramon.

like the problem may be platforms setting this to 1 when really it
> should be higher _even_if_ the memory space in question is contiguous.
> Yes, you've always been able to say we have 1 bank of N physical chips
> and it's been OK, but now I guess we're finally hitting the point where
> that doesn't work.
>
> >
> > [1] https://lwn.net/Articles/749064/
> >
> > > Fixes: 2a1f4f1758b5 ("Revert "fdt_support: Use CONFIG_NR_DRAM_BANKS if
> > > defined"")
> > >
> > > Signed-off-by: Ramon Fried <ramon.fried at intel.com>
> > > ---
> > >  common/fdt_support.c | 9 ++-------
> > >  1 file changed, 2 insertions(+), 7 deletions(-)
> > >
> > > diff --git a/common/fdt_support.c b/common/fdt_support.c
> > > index 34d2bd5..e898236 100644
> > > --- a/common/fdt_support.c
> > > +++ b/common/fdt_support.c
> > > @@ -409,19 +409,14 @@ static int fdt_pack_reg(const void *fdt, void
> *buf, u64 *address, u64 *size,
> > >         return p - (char *)buf;
> > >  }
> > >
> > > -#define MEMORY_BANKS_MAX 4
> > >  int fdt_fixup_memory_banks(void *blob, u64 start[], u64 size[], int
> banks)
> > >  {
> > >         int err, nodeoffset;
> > >         int len, i;
> > > -       u8 tmp[MEMORY_BANKS_MAX * 16]; /* Up to 64-bit address +
> 64-bit size */
> > > +       u8 tmp[banks * 16]; /* Up to 64-bit address + 64-bit size */
> > >
> > > -       if (banks > MEMORY_BANKS_MAX) {
> > > -               printf("%s: num banks %d exceeds hardcoded limit %d."
> > > -                      " Recompile with higher MEMORY_BANKS_MAX?\n",
> > > -                      __FUNCTION__, banks, MEMORY_BANKS_MAX);
> > > +       if (!banks)
> > >                 return -1;
> > > -       }
> > >
> > >         err = fdt_check_header(blob);
> > >         if (err < 0) {
> > > --
> > > 2.7.4
> > >
> > > _______________________________________________
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> > > U-Boot at lists.denx.de
> > > https://lists.denx.de/listinfo/u-boot
>
> --
> Tom
>