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authorClaudiu Beznea <claudiu.beznea@microchip.com>2018-08-30 13:50:06 +0200
committerSebastian Reichel <sre@kernel.org>2018-09-16 12:31:48 +0200
commit9f7195da31fb0b0f83dbd6bbe7aa98c889fb865a (patch)
treeb2e2bf2d4a306afc2fc84de7cbebae3fa1106062 /arch/arm/mach-at91
parentLinux 4.19-rc1 (diff)
downloadlinux-9f7195da31fb0b0f83dbd6bbe7aa98c889fb865a.tar.xz
linux-9f7195da31fb0b0f83dbd6bbe7aa98c889fb865a.zip
power: reset: at91-poweroff: switch to slow clock before shutdown
The SAMA5D2 NRST input signal is resynchronized with the SLCK clock and it can take up to 2 SLCK cycles (about 90us) for the internal reset to be effective. During this delay, the VDDCORE current consumption may still be high (application-dependent) with the VDDCORE regulator already OFF. Under such conditions, VDDCORE may operate below its operating range leading to potential register corruption. To prevent such situation, it is recommended to decrease significantly the power consumption of the device once the voltage regulator is turned-off. This can be achieved by operating the device at a much lower low frequency. To solve this switch the master clock to slock clock just before writing shutdown command to shutdown controller. Signed-off-by: Claudiu Beznea <claudiu.beznea@microchip.com> Suggested-by: Patrice Vilchez <patrice.vilchez@microchip.com> Acked-by: Nicolas Ferre <nicolas.ferre@microchip.com> Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>
Diffstat (limited to 'arch/arm/mach-at91')
-rw-r--r--arch/arm/mach-at91/pm_suspend.S8
1 files changed, 8 insertions, 0 deletions
diff --git a/arch/arm/mach-at91/pm_suspend.S b/arch/arm/mach-at91/pm_suspend.S
index a7c6ae13c945..bfe1c4d06901 100644
--- a/arch/arm/mach-at91/pm_suspend.S
+++ b/arch/arm/mach-at91/pm_suspend.S
@@ -149,6 +149,14 @@ exit_suspend:
ENDPROC(at91_pm_suspend_in_sram)
ENTRY(at91_backup_mode)
+ /* Switch the master clock source to slow clock. */
+ ldr pmc, .pmc_base
+ ldr tmp1, [pmc, #AT91_PMC_MCKR]
+ bic tmp1, tmp1, #AT91_PMC_CSS
+ str tmp1, [pmc, #AT91_PMC_MCKR]
+
+ wait_mckrdy
+
/*BUMEN*/
ldr r0, .sfr
mov tmp1, #0x1