ARM: at91: pm: save ddr phy calibration data to securam

The resuming from backup mode is done with the help of bootloader.
The bootloader reconfigure the DDR controller and DDR PHY controller.
To speed-up the resuming process save the PHY calibration data into
SECURAM before suspending (securam is powered on backup mode).
This data will be later used by bootloader in DDR PHY reconfiguration
process. Also, in the process or recalibration the first 8 words of
the memory may get corrupted. To solve this, these 8 words are saved
in the securam and restored by bootloader in the process of PHY
configuration.

Signed-off-by: Claudiu Beznea <claudiu.beznea@microchip.com>
Signed-off-by: Nicolas Ferre <nicolas.ferre@microchip.com>
Link: https://lore.kernel.org/r/20210415105010.569620-20-claudiu.beznea@microchip.com

arch/arm/mach-at91/pm.c

@@ -10,6 +10,7 @@
 #include <linux/io.h>
 #include <linux/of_address.h>
 #include <linux/of.h>
+#include <linux/of_fdt.h>
 #include <linux/of_platform.h>
 #include <linux/parser.h>
 #include <linux/suspend.h>
@@ -27,18 +28,23 @@
 #include "generic.h"
 #include "pm.h"
 
+#define BACKUP_DDR_PHY_CALIBRATION	(9)
+
 /**
  * struct at91_pm_bu - AT91 power management backup unit data structure
  * @suspended: true if suspended to backup mode
  * @reserved: reserved
  * @canary: canary data for memory checking after exit from backup mode
  * @resume: resume API
+ * @ddr_phy_calibration: DDR PHY calibration data: ZQ0CR0, first 8 words
+ * of the memory
  */
 struct at91_pm_bu {
 	int suspended;
 	unsigned long reserved;
 	phys_addr_t canary;
 	phys_addr_t resume;
+	unsigned long ddr_phy_calibration[BACKUP_DDR_PHY_CALIBRATION];
 };
 
 /**
@@ -48,6 +54,7 @@ struct at91_pm_bu {
  * @ws_ids: wakup sources of_device_id array
  * @data: PM data to be used on last phase of suspend
  * @bu: backup unit mapped data (for backup mode)
+ * @memcs: memory chip select
  */
 struct at91_soc_pm {
 	int (*config_shdwc_ws)(void __iomem *shdwc, u32 *mode, u32 *polarity);
@@ -55,6 +62,7 @@ struct at91_soc_pm {
 	const struct of_device_id *ws_ids;
 	struct at91_pm_bu *bu;
 	struct at91_pm_data data;
+	void *memcs;
 };
 
 /**
@@ -316,6 +324,19 @@ extern u32 at91_pm_suspend_in_sram_sz;
 
 static int at91_suspend_finish(unsigned long val)
 {
+	int i;
+
+	if (soc_pm.data.mode == AT91_PM_BACKUP && soc_pm.data.ramc_phy) {
+		/*
+		 * The 1st 8 words of memory might get corrupted in the process
+		 * of DDR PHY recalibration; it is saved here in securam and it
+		 * will be restored later, after recalibration, by bootloader
+		 */
+		for (i = 1; i < BACKUP_DDR_PHY_CALIBRATION; i++)
+			soc_pm.bu->ddr_phy_calibration[i] =
+				*((unsigned int *)soc_pm.memcs + (i - 1));
+	}
+
 	flush_cache_all();
 	outer_disable();
 
@@ -673,12 +694,40 @@ static bool __init at91_is_pm_mode_active(int pm_mode)
 		soc_pm.data.suspend_mode == pm_mode);
 }
 
+static int __init at91_pm_backup_scan_memcs(unsigned long node,
+					    const char *uname, int depth,
+					    void *data)
+{
+	const char *type;
+	const __be32 *reg;
+	int *located = data;
+	int size;
+
+	/* Memory node already located. */
+	if (*located)
+		return 0;
+
+	type = of_get_flat_dt_prop(node, "device_type", NULL);
+
+	/* We are scanning "memory" nodes only. */
+	if (!type || strcmp(type, "memory"))
+		return 0;
+
+	reg = of_get_flat_dt_prop(node, "reg", &size);
+	if (reg) {
+		soc_pm.memcs = __va((phys_addr_t)be32_to_cpu(*reg));
+		*located = 1;
+	}
+
+	return 0;
+}
+
 static int __init at91_pm_backup_init(void)
 {
 	struct gen_pool *sram_pool;
 	struct device_node *np;
 	struct platform_device *pdev;
-	int ret = -ENODEV;
+	int ret = -ENODEV, located = 0;
 
 	if (!IS_ENABLED(CONFIG_SOC_SAMA5D2))
 		return -EPERM;
@@ -713,6 +762,15 @@ static int __init at91_pm_backup_init(void)
 	soc_pm.bu->suspended = 0;
 	soc_pm.bu->canary = __pa_symbol(&canary);
 	soc_pm.bu->resume = __pa_symbol(cpu_resume);
+	if (soc_pm.data.ramc_phy) {
+		of_scan_flat_dt(at91_pm_backup_scan_memcs, &located);
+		if (!located)
+			goto securam_fail;
+
+		/* DDR3PHY_ZQ0SR0 */
+		soc_pm.bu->ddr_phy_calibration[0] = readl(soc_pm.data.ramc_phy +
+							  0x188);
+	}
 
 	return 0;