Re: [PATCH 2/2] power/reset: at91-poweroff: timely shitdown LPDDR memories

Alexandre Belloni
2016-10-13T11:03:17Z

On 12/10/2016 at 14:48:27 +0200, Jean-Jacques Hiblot wrote :
> > +static void at91_lpddr_poweroff(void)
> > +{
> > + asm volatile(
> > + /* Align to cache lines */
> > + ".balign 32\n\t"
> > +
> > + " ldr r6, [%2, #" __stringify(AT91_SHDW_CR) "]\n\t"
> At first sight, it looks useless. I assume it's used to preload the
> TLB before the LPDDR is turned off.
> A comment to explain why this line is useful would prevent its removal.

Yes, this is the case. I can add a comment.

Anyway, I would prefer the whole thing to run from SRAM, as a PIE
instead of relying on the cache.

> > + ddr_type = readl(mpddrc_base + AT91_DDRSDRC_MDR) & AT91_DDRSDRC_MD;
> > + if ((ddr_type == AT91_DDRSDRC_MD_LPDDR2) ||
> > + (ddr_type == AT91_DDRSDRC_MD_LPDDR3))
> Souldn't there be something like "pm_power_off = at91_lpddr_poweroff;" here ?
>

Indeed

--
Alexandre Belloni, Free Electrons
Embedded Linux and Kernel engineering