[PATCH v5 02/15] clk: at91: pmc: execute suspend/resume only for backup mode

[Claudiu Beznea <claudiu.beznea@microchip.com>]

Before going to backup mode architecture specific PM code sets the first
word in securam (file arch/arm/mach-at91/pm.c, function at91_pm_begin()).
Thus take this into account when suspending/resuming clocks. This will
avoid executing unnecessary instructions when suspending to non backup
modes.

Signed-off-by: Claudiu Beznea <claudiu.beznea@microchip.com>
---
 drivers/clk/at91/pmc.c | 39 +++++++++++++++++++++++++++++++++++++++
 1 file changed, 39 insertions(+)

diff --git a/drivers/clk/at91/pmc.c b/drivers/clk/at91/pmc.c
index b2806946a77a..517973062719 100644
--- a/drivers/clk/at91/pmc.c
+++ b/drivers/clk/at91/pmc.c
@@ -8,6 +8,7 @@
 #include <linux/clkdev.h>
 #include <linux/clk/at91_pmc.h>
 #include <linux/of.h>
+#include <linux/of_address.h>
 #include <linux/mfd/syscon.h>
 #include <linux/platform_device.h>
 #include <linux/regmap.h>
@@ -110,13 +111,35 @@ struct pmc_data *pmc_data_allocate(unsigned int ncore, unsigned int nsystem,
 }
 
 #ifdef CONFIG_PM
+
+/* Address in SECURAM that say if we suspend to backup mode. */
+static void __iomem *at91_pmc_backup_suspend;
+
 static int at91_pmc_suspend(void)
 {
+	unsigned int backup;
+
+	if (!at91_pmc_backup_suspend)
+		return 0;
+
+	backup = readl_relaxed(at91_pmc_backup_suspend);
+	if (!backup)
+		return 0;
+
 	return clk_save_context();
 }
 
 static void at91_pmc_resume(void)
 {
+	unsigned int backup;
+
+	if (!at91_pmc_backup_suspend)
+		return;
+
+	backup = readl_relaxed(at91_pmc_backup_suspend);
+	if (!backup)
+		return;
+
 	clk_restore_context();
 }
 
@@ -144,6 +167,22 @@ static int __init pmc_register_ops(void)
 	}
 	of_node_put(np);
 
+	np = of_find_compatible_node(NULL, NULL, "atmel,sama5d2-securam");
+	if (!np)
+		return -ENODEV;
+
+	if (!of_device_is_available(np)) {
+		of_node_put(np);
+		return -ENODEV;
+	}
+	of_node_put(np);
+
+	at91_pmc_backup_suspend = of_iomap(np, 0);
+	if (!at91_pmc_backup_suspend) {
+		pr_warn("%s(): unable to map securam\n", __func__);
+		return -ENOMEM;
+	}
+
 	register_syscore_ops(&pmc_syscore_ops);
 
 	return 0;
-- 
2.25.1