[U-Boot] [PATCH v2] arm: socfpga: do not reboot via SRAM

[Simon Goldschmidt]

On Fri, Jul 12, 2019 at 7:15 AM Marek Vasut <marex at denx.de> wrote:
>
> On 7/10/19 9:06 PM, Simon Goldschmidt wrote:
> > This removes the code that enables the Boot ROM to just jump to SRAM
> > instead of loading SPL from the original boot source on warm reboot.
> >
> > The reason for removing this is that it is insecure: SRAM might be
> > overwritten at the time the warm reboot is done. Instead, use the default
> > behaviour of loading SPL from the configured boot source medium.
> >
> > Signed-off-by: Simon Goldschmidt <simon.k.r.goldschmidt at gmail.com>
> > ---
> >
> > Changes in v2:
> > - remove the compatibility code restoring the old "reboot from SRAM"
> >   behaviour via an env var callback as it turned out such a hack should
> >   not be included by default
> > - (v1 patch subject was: "arm: socfpga: control reboot from SRAM via env
> >   callback")
> >
> >  arch/arm/mach-socfpga/misc_gen5.c | 10 +---------
> >  1 file changed, 1 insertion(+), 9 deletions(-)
> >
> > diff --git a/arch/arm/mach-socfpga/misc_gen5.c b/arch/arm/mach-socfpga/misc_gen5.c
> > index 71547d81ab..38bff8a450 100644
> > --- a/arch/arm/mach-socfpga/misc_gen5.c
> > +++ b/arch/arm/mach-socfpga/misc_gen5.c
> > @@ -6,6 +6,7 @@
> >  #include <common.h>
> >  #include <asm/io.h>
> >  #include <errno.h>
> > +#include <environment.h>
> >  #include <fdtdec.h>
> >  #include <linux/libfdt.h>
> >  #include <altera.h>
> > @@ -182,15 +183,6 @@ int arch_early_init_r(void)
> >  {
> >       int i;
> >
> > -     /*
> > -      * Write magic value into magic register to unlock support for
> > -      * issuing warm reset. The ancient kernel code expects this
> > -      * value to be written into the register by the bootloader, so
> > -      * to support that old code, we write it here instead of in the
> > -      * reset_cpu() function just before resetting the CPU.
> > -      */
> > -     writel(0xae9efebc, &sysmgr_regs->romcodegrp_warmramgrp_enable);
>
> Does this break ancient altera kernel versions ? Do we care ?

You mean ancient kernels built from non-mainline sources? I don't really care,
no.

However, this *might* break boards like my older hw revisions that set qspi into
four byte mode. But given that, depending on the situation, those *are* already
broken, I think removing this code is still the correct thing to do.

The bonus is that you'll notice on the very first try that 'reboot' doesn't
work. Whereas before,t it worked at the start and then might break in some
specific situation you'll not be able to test.

Regards,
Simon