[PATCH 4.4 23/26] power: reset: at91-poweroff: timely shutdown LPDDR memories

Greg Kroah-Hartman
2017-04-06T09:36:02Z

From: Alexandre Belloni <alexandre.belloni@free-electrons.com>

commit 0b0408745e7ff24757cbfd571d69026c0ddb803c upstream.

LPDDR memories can only handle up to 400 uncontrolled power off. Ensure the
proper power off sequence is used before shutting down the platform.

Signed-off-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>
Signed-off-by: Sebastian Reichel <sre@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
drivers/power/reset/at91-poweroff.c | 54 +++++++++++++++++++++++++++++++++++-
1 file changed, 53 insertions(+), 1 deletion(-)

--- a/drivers/power/reset/at91-poweroff.c
+++ b/drivers/power/reset/at91-poweroff.c
@@ -14,9 +14,12 @@
#include <linux/io.h>
#include <linux/module.h>
#include <linux/of.h>
+#include <linux/of_address.h>
#include <linux/platform_device.h>
#include <linux/printk.h>

+#include <soc/at91/at91sam9_ddrsdr.h>
+
#define AT91_SHDW_CR 0x00 /* Shut Down Control Register */
#define AT91_SHDW_SHDW BIT(0) /* Shut Down command */
#define AT91_SHDW_KEY (0xa5 << 24) /* KEY Password */
@@ -50,6 +53,7 @@ static const char *shdwc_wakeup_modes[]

static void __iomem *at91_shdwc_base;
static struct clk *sclk;
+static void __iomem *mpddrc_base;

static void __init at91_wakeup_status(void)
{
@@ -73,6 +77,29 @@ static void at91_poweroff(void)
writel(AT91_SHDW_KEY | AT91_SHDW_SHDW, at91_shdwc_base + AT91_SHDW_CR);
}

+static void at91_lpddr_poweroff(void)
+{
+ asm volatile(
+ /* Align to cache lines */
+ ".balign 32\n\t"
+
+ /* Ensure AT91_SHDW_CR is in the TLB by reading it */
+ " ldr r6, [%2, #" __stringify(AT91_SHDW_CR) "]\n\t"
+
+ /* Power down SDRAM0 */
+ " str %1, [%0, #" __stringify(AT91_DDRSDRC_LPR) "]\n\t"
+ /* Shutdown CPU */
+ " str %3, [%2, #" __stringify(AT91_SHDW_CR) "]\n\t"
+
+ " b .\n\t"
+ :
+ : "r" (mpddrc_base),
+ "r" cpu_to_le32(AT91_DDRSDRC_LPDDR2_PWOFF),
+ "r" (at91_shdwc_base),
+ "r" cpu_to_le32(AT91_SHDW_KEY | AT91_SHDW_SHDW)
+ : "r0");
+}
+
static int at91_poweroff_get_wakeup_mode(struct device_node *np)
{
const char *pm;
@@ -124,6 +151,8 @@ static void at91_poweroff_dt_set_wakeup_
static int __init at91_poweroff_probe(struct platform_device *pdev)
{
struct resource *res;
+ struct device_node *np;
+ u32 ddr_type;
int ret;

res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
@@ -150,12 +179,30 @@ static int __init at91_poweroff_probe(st

pm_power_off = at91_poweroff;

+ np = of_find_compatible_node(NULL, NULL, "atmel,sama5d3-ddramc");
+ if (!np)
+ return 0;
+
+ mpddrc_base = of_iomap(np, 0);
+ of_node_put(np);
+
+ if (!mpddrc_base)
+ return 0;
+
+ ddr_type = readl(mpddrc_base + AT91_DDRSDRC_MDR) & AT91_DDRSDRC_MD;
+ if ((ddr_type == AT91_DDRSDRC_MD_LPDDR2) ||
+ (ddr_type == AT91_DDRSDRC_MD_LPDDR3))
+ pm_power_off = at91_lpddr_poweroff;
+ else
+ iounmap(mpddrc_base);
+
return 0;
}

static int __exit at91_poweroff_remove(struct platform_device *pdev)
{
- if (pm_power_off == at91_poweroff)
+ if (pm_power_off == at91_poweroff ||
+ pm_power_off == at91_lpddr_poweroff)
pm_power_off = NULL;

clk_disable_unprepare(sclk);
@@ -163,6 +210,11 @@ static int __exit at91_poweroff_remove(s
return 0;
}

+static const struct of_device_id at91_ramc_of_match[] = {
+ { .compatible = "atmel,sama5d3-ddramc", },
+ { /* sentinel */ }
+};
+
static const struct of_device_id at91_poweroff_of_match[] = {
{ .compatible = "atmel,at91sam9260-shdwc", },
{ .compatible = "atmel,at91sam9rl-shdwc", },