ARM: at91: pm: add backup mode support for SAMA7G5

Adapt at91_pm_backup_init() to work for SAMA7G5. Also, set the LPM pin
to shutdown controller. This will signal to PMIC that it needs to switch
to the state corresponding to backup mode.
Signed-off-by: Claudiu Beznea <claudiu.beznea@microchip.com>
Signed-off-by: Nicolas Ferre <nicolas.ferre@microchip.com>
Link: https://lore.kernel.org/r/20210415105010.569620-21-claudiu.beznea@microchip.com

arch/arm/mach-at91/pm.c

@@ -729,7 +729,8 @@ static int __init at91_pm_backup_init(void)
 	struct platform_device *pdev;
 	int ret = -ENODEV, located = 0;
 
-	if (!IS_ENABLED(CONFIG_SOC_SAMA5D2))
+	if (!IS_ENABLED(CONFIG_SOC_SAMA5D2) &&
+	    !IS_ENABLED(CONFIG_SOC_SAMA7G5))
 		return -EPERM;
 
 	if (!at91_is_pm_mode_active(AT91_PM_BACKUP))

arch/arm/mach-at91/pm_suspend.S

@@ -106,6 +106,12 @@ lp_done_\ena:
 #endif
 	.endm
 
+	.macro at91_backup_set_lpm reg
+#ifdef CONFIG_SOC_SAMA7
+	orr	\reg, \reg, #0x200000
+#endif
+	.endm
+
 	.text
 
 	.arm
@@ -989,6 +995,7 @@ ulp_exit:
 	ldr	r0, .shdwc
 	mov	tmp1, #0xA5000000
 	add	tmp1, tmp1, #0x1
+	at91_backup_set_lpm tmp1
 	str	tmp1, [r0, #0]
 .endm