Re: [PATCH 4.4 23/26] power: reset: at91-poweroff: timely shutdown LPDDR memories

Ben Hutchings
2017-04-06T17:46:03Z

On Thu, 2017-04-06 at 10:38 +0200, Greg Kroah-Hartman wrote:
> 4.4-stable review patch. If anyone has any objections, please let me know.
>
> ------------------
>
> From: Alexandre Belloni <alexandre.belloni@free-electrons.com>
>
> commit 0b0408745e7ff24757cbfd571d69026c0ddb803c upstream.
>
> LPDDR memories can only handle up to 400 uncontrolled power off. Ensure the
> proper power off sequence is used before shutting down the platform.
>
> Signed-off-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>
> Signed-off-by: Sebastian Reichel <sre@kernel.org>
> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
[...]
> +static void at91_lpddr_poweroff(void)
> +{
> + asm volatile(
> + /* Align to cache lines */
> + ".balign 32\n\t"
> +
> + /* Ensure AT91_SHDW_CR is in the TLB by reading it */
> + " ldr r6, [%2, #" __stringify(AT91_SHDW_CR) "]\n\t"

This clobbers r6...

> + /* Power down SDRAM0 */
> + " str %1, [%0, #" __stringify(AT91_DDRSDRC_LPR) "]\n\t"
> + /* Shutdown CPU */
> + " str %3, [%2, #" __stringify(AT91_SHDW_CR) "]\n\t"
> +
> + " b .\n\t"
> + :
> + : "r" (mpddrc_base),
> + "r" cpu_to_le32(AT91_DDRSDRC_LPDDR2_PWOFF),
> + "r" (at91_shdwc_base),
> + "r" cpu_to_le32(AT91_SHDW_KEY | AT91_SHDW_SHDW)
> + : "r0");
[...]

...but the clobber list has r0.

Ben.

--
Ben Hutchings
Software Developer, Codethink Ltd.