5.15-stable review patch. If anyone has any objections, please let me know.
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From: Nicolas Ferre nicolas.ferre@microchip.com
[ Upstream commit 6fc5bdfa872b7da51b5507a1327a17c3db2fcf95 ]
Change how the Backup Unit Power is configured and force the automatic/hardware mode. This change eliminates the need for software management of the power switch, ensuring it transitions to the backup power source before entering low power modes.
This is done in the only location where this switch was configured. It's usually done in the bootloader.
Previously, the loss of the VDDANA (or VDDIN33) power source was not automatically compensated by an alternative power source. This resulted in the loss of Backup Unit content, including Backup Self-refresh low power mode information, OTP emulation configuration, and boot configuration, for instance.
Fixes: ac809e7879b1 ("ARM: at91: pm: switch backup area to vbat in backup mode") Signed-off-by: Nicolas Ferre nicolas.ferre@microchip.com Link: https://lore.kernel.org/r/20241125165648.509162-1-nicolas.ferre@microchip.co... Signed-off-by: Claudiu Beznea claudiu.beznea@tuxon.dev Signed-off-by: Sasha Levin sashal@kernel.org --- arch/arm/mach-at91/pm.c | 31 ++++++++++++++++++++----------- 1 file changed, 20 insertions(+), 11 deletions(-)
diff --git a/arch/arm/mach-at91/pm.c b/arch/arm/mach-at91/pm.c index c8cc993ca8ca1..91efc3d4de61d 100644 --- a/arch/arm/mach-at91/pm.c +++ b/arch/arm/mach-at91/pm.c @@ -403,7 +403,21 @@ static int at91_suspend_finish(unsigned long val) return 0; }
-static void at91_pm_switch_ba_to_vbat(void) +/** + * at91_pm_switch_ba_to_auto() - Configure Backup Unit Power Switch + * to automatic/hardware mode. + * + * The Backup Unit Power Switch can be managed either by software or hardware. + * Enabling hardware mode allows the automatic transition of power between + * VDDANA (or VDDIN33) and VDDBU (or VBAT, respectively), based on the + * availability of these power sources. + * + * If the Backup Unit Power Switch is already in automatic mode, no action is + * required. If it is in software-controlled mode, it is switched to automatic + * mode to enhance safety and eliminate the need for toggling between power + * sources. + */ +static void at91_pm_switch_ba_to_auto(void) { unsigned int offset = offsetof(struct at91_pm_sfrbu_regs, pswbu); unsigned int val; @@ -414,24 +428,19 @@ static void at91_pm_switch_ba_to_vbat(void)
val = readl(soc_pm.data.sfrbu + offset);
- /* Already on VBAT. */ - if (!(val & soc_pm.sfrbu_regs.pswbu.state)) + /* Already on auto/hardware. */ + if (!(val & soc_pm.sfrbu_regs.pswbu.ctrl)) return;
- val &= ~soc_pm.sfrbu_regs.pswbu.softsw; - val |= soc_pm.sfrbu_regs.pswbu.key | soc_pm.sfrbu_regs.pswbu.ctrl; + val &= ~soc_pm.sfrbu_regs.pswbu.ctrl; + val |= soc_pm.sfrbu_regs.pswbu.key; writel(val, soc_pm.data.sfrbu + offset); - - /* Wait for update. */ - val = readl(soc_pm.data.sfrbu + offset); - while (val & soc_pm.sfrbu_regs.pswbu.state) - val = readl(soc_pm.data.sfrbu + offset); }
static void at91_pm_suspend(suspend_state_t state) { if (soc_pm.data.mode == AT91_PM_BACKUP) { - at91_pm_switch_ba_to_vbat(); + at91_pm_switch_ba_to_auto();
cpu_suspend(0, at91_suspend_finish);