ARM: at91: pm: use the mmio-sram pool to access SRAM

Now that the SRAM is part of a genpool, use it to allocate memory to use for the
slowclock implementation.
Signed-off-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>
Signed-off-by: Nicolas Ferre <nicolas.ferre@atmel.com>

arch/arm/mach-at91/Kconfig

@@ -178,6 +178,7 @@ comment "AT91 Feature Selections"
 
 config AT91_SLOW_CLOCK
 	bool "Suspend-to-RAM disables main oscillator"
+	select SRAM
 	depends on SUSPEND
 	help
 	  Select this if you want Suspend-to-RAM to save the most power

arch/arm/mach-at91/pm.c

@@ -14,10 +14,12 @@
 #include <linux/suspend.h>
 #include <linux/sched.h>
 #include <linux/proc_fs.h>
+#include <linux/genalloc.h>
 #include <linux/interrupt.h>
 #include <linux/sysfs.h>
 #include <linux/module.h>
 #include <linux/of.h>
+#include <linux/of_platform.h>
 #include <linux/platform_device.h>
 #include <linux/io.h>
 #include <linux/clk/at91_pmc.h>
@@ -222,10 +224,52 @@ void at91_pm_set_standby(void (*at91_standby)(void))
 	}
 }
 
+#ifdef CONFIG_AT91_SLOW_CLOCK
+static void __init at91_pm_sram_init(void)
+{
+	struct gen_pool *sram_pool;
+	phys_addr_t sram_pbase;
+	unsigned long sram_base;
+	struct device_node *node;
+	struct platform_device *pdev;
+
+	node = of_find_compatible_node(NULL, NULL, "mmio-sram");
+	if (!node) {
+		pr_warn("%s: failed to find sram node!\n", __func__);
+		return;
+	}
+
+	pdev = of_find_device_by_node(node);
+	if (!pdev) {
+		pr_warn("%s: failed to find sram device!\n", __func__);
+		goto put_node;
+	}
+
+	sram_pool = dev_get_gen_pool(&pdev->dev);
+	if (!sram_pool) {
+		pr_warn("%s: sram pool unavailable!\n", __func__);
+		goto put_node;
+	}
+
+	sram_base = gen_pool_alloc(sram_pool, at91_slow_clock_sz);
+	if (!sram_base) {
+		pr_warn("%s: unable to alloc ocram!\n", __func__);
+		goto put_node;
+	}
+
+	sram_pbase = gen_pool_virt_to_phys(sram_pool, sram_base);
+	slow_clock = __arm_ioremap_exec(sram_pbase, at91_slow_clock_sz, false);
+
+put_node:
+	of_node_put(node);
+}
+#endif
+
+
 static int __init at91_pm_init(void)
 {
 #ifdef CONFIG_AT91_SLOW_CLOCK
-	slow_clock = (void *) (AT91_IO_VIRT_BASE - at91_slow_clock_sz);
+	at91_pm_sram_init();
 #endif
 
 	pr_info("AT91: Power Management%s\n", (slow_clock ? " (with slow clock mode)" : ""));