[PATCH v3 4/9] arm: armv7: save boot arguments

[Raymond Mao]

Hi Simon,

On Thu, 28 Dec 2023 at 08:37, Simon Glass <sjg at chromium.org> wrote:

> Hi Raymond,
>
> On Wed, Dec 27, 2023 at 3:52 PM Raymond Mao <raymond.mao at linaro.org>
> wrote:
> >
> > Hi Simon,
> >
> > On Tue, 26 Dec 2023 at 04:48, Simon Glass <sjg at chromium.org> wrote:
> >>
> >> Hi Raymond,
> >>
> >> On Fri, Dec 22, 2023 at 9:31 PM Raymond Mao <raymond.mao at linaro.org>
> wrote:
> >> >
> >> > Save boot arguments r[0-3] into an array for handover of bloblist from
> >> > previous boot stage.
> >> >
> >> > Signed-off-by: Raymond Mao <raymond.mao at linaro.org>
> >> > ---
> >> > Changes in v2
> >> > - New patch file created for v2.
> >> > Changes in v3
> >> > - Swap value of r0 with r2.
> >> >
> >> >  arch/arm/cpu/armv7/start.S | 13 +++++++++++++
> >> >  1 file changed, 13 insertions(+)
> >> >
> >> > diff --git a/arch/arm/cpu/armv7/start.S b/arch/arm/cpu/armv7/start.S
> >> > index 69e281b086..2ca63ca32c 100644
> >> > --- a/arch/arm/cpu/armv7/start.S
> >> > +++ b/arch/arm/cpu/armv7/start.S
> >> > @@ -152,9 +152,22 @@ ENDPROC(c_runtime_cpu_setup)
> >> >   *
> >> >
>  *************************************************************************/
> >> >  WEAK(save_boot_params)
> >> > +#if (IS_ENABLED(CONFIG_OF_BOARD) && IS_ENABLED(CONFIG_BLOBLIST))
> >> > +       ldr r12, =saved_args
> >> > +       /* Intentionally swapping r0 with r2 */
> >> > +       stm r12, {r2, r1, r0, r3}
> >>
> >> I thought the instruction was a bitmap, so what does the 'swapping'
> >> actually change?
> >>
> > The swapping is due to different register conventions between aarch32
> and aarch64.
> > Actually swapping here is to avoid the complexity of swapping this in C
> code.
> > I will update the comments here.
> >
> > [...]
>
> But how does this work? stm does not support changing the
> ordering...what am I missing?
>

Ah, my bad. You are right. I have to use `str` to store one by one in this
case.

[...]

Thanks and regards,
Raymond