ARM: at91: pm: Add sama5d2 backup mode

The sama5d2 has a mode were it is possible to cut power to the SoC while
keeping the RAM in self refresh.
Resuming from that mode needs support in the firmware/bootloader.

Signed-off-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>
Acked-by: Wenyou Yang <wenyou.yang@atmel.com>

arch/arm/mach-at91/pm.c

@@ -22,6 +22,7 @@
 #include <asm/cacheflush.h>
 #include <asm/fncpy.h>
 #include <asm/system_misc.h>
+#include <asm/suspend.h>
 
 #include "generic.h"
 #include "pm.h"
@@ -58,6 +59,14 @@ static int at91_pm_valid_state(suspend_state_t state)
 	}
 }
 
+static int canary = 0xA5A5A5A5;
+
+static struct at91_pm_bu {
+	int suspended;
+	unsigned long reserved;
+	phys_addr_t canary;
+	phys_addr_t resume;
+} *pm_bu;
 
 static suspend_state_t target_state;
 
@@ -123,15 +132,39 @@ static void (*at91_suspend_sram_fn)(struct at91_pm_data *);
 extern void at91_pm_suspend_in_sram(struct at91_pm_data *pm_data);
 extern u32 at91_pm_suspend_in_sram_sz;
 
-static void at91_pm_suspend(suspend_state_t state)
+static int at91_suspend_finish(unsigned long val)
 {
-	pm_data.mode = (state == PM_SUSPEND_MEM) ? AT91_PM_SLOW_CLOCK : 0;
-
 	flush_cache_all();
 	outer_disable();
 
 	at91_suspend_sram_fn(&pm_data);
 
+	return 0;
+}
+
+static void at91_pm_suspend(suspend_state_t state)
+{
+	if (pm_data.deepest_state == AT91_PM_BACKUP)
+		if (state == PM_SUSPEND_MEM)
+			pm_data.mode = AT91_PM_BACKUP;
+		else
+			pm_data.mode = AT91_PM_SLOW_CLOCK;
+	else
+		pm_data.mode = (state == PM_SUSPEND_MEM) ? AT91_PM_SLOW_CLOCK : 0;
+
+	if (pm_data.mode == AT91_PM_BACKUP) {
+		pm_bu->suspended = 1;
+
+		cpu_suspend(0, at91_suspend_finish);
+
+		/* The SRAM is lost between suspend cycles */
+		at91_suspend_sram_fn = fncpy(at91_suspend_sram_fn,
+					     &at91_pm_suspend_in_sram,
+					     at91_pm_suspend_in_sram_sz);
+	} else {
+		at91_suspend_finish(0);
+	}
+
 	outer_resume();
 }
 
@@ -436,6 +469,70 @@ static void __init at91_pm_sram_init(void)
 			&at91_pm_suspend_in_sram, at91_pm_suspend_in_sram_sz);
 }
 
+static void __init at91_pm_backup_init(void)
+{
+	struct gen_pool *sram_pool;
+	struct device_node *np;
+	struct platform_device *pdev = NULL;
+
+	pm_bu = NULL;
+
+	np = of_find_compatible_node(NULL, NULL, "atmel,sama5d2-shdwc");
+	if (!np) {
+		pr_warn("%s: failed to find shdwc!\n", __func__);
+		return;
+	}
+
+	pm_data.shdwc = of_iomap(np, 0);
+	of_node_put(np);
+
+	np = of_find_compatible_node(NULL, NULL, "atmel,sama5d2-sfrbu");
+	if (!np) {
+		pr_warn("%s: failed to find sfrbu!\n", __func__);
+		goto sfrbu_fail;
+	}
+
+	pm_data.sfrbu = of_iomap(np, 0);
+	of_node_put(np);
+	pm_bu = NULL;
+
+	np = of_find_compatible_node(NULL, NULL, "atmel,sama5d2-securam");
+	if (!np)
+		goto securam_fail;
+
+	pdev = of_find_device_by_node(np);
+	of_node_put(np);
+	if (!pdev) {
+		pr_warn("%s: failed to find securam device!\n", __func__);
+		goto securam_fail;
+	}
+
+	sram_pool = gen_pool_get(&pdev->dev, NULL);
+	if (!sram_pool) {
+		pr_warn("%s: securam pool unavailable!\n", __func__);
+		goto securam_fail;
+	}
+
+	pm_bu = (void *)gen_pool_alloc(sram_pool, sizeof(struct at91_pm_bu));
+	if (!pm_bu) {
+		pr_warn("%s: unable to alloc securam!\n", __func__);
+		goto securam_fail;
+	}
+
+	pm_bu->suspended = 0;
+	pm_bu->canary = virt_to_phys(&canary);
+	pm_bu->resume = virt_to_phys(cpu_resume);
+
+	return;
+
+sfrbu_fail:
+	iounmap(pm_data.shdwc);
+	pm_data.shdwc = NULL;
+securam_fail:
+	iounmap(pm_data.sfrbu);
+	pm_data.sfrbu = NULL;
+}
+
 struct pmc_info {
 	unsigned long uhp_udp_mask;
 };
@@ -510,3 +607,9 @@ void __init sama5_pm_init(void)
 	at91_dt_ramc();
 	at91_pm_init(NULL);
 }
+
+void __init sama5d2_pm_init(void)
+{
+	at91_pm_backup_init();
+	sama5_pm_init();
+}