The DDR controller can detect idle periods and leverage low power
features clock stop. When new requests occur, the DDRC resumes
normal operation.
Signed-off-by: Soren Brinkmann <soren.brinkmann@xxxxxxxxxx>
---
v2:
- properly document return value for zynq_pm_ioremap
- change zynq_pm_late_init signature to return void
- add kernel doc to late_init()
- fix kernel doc
- only enable clock-stop during boot and leave out self-refresh. The
self-refresh penalty is apparently not-negligible
---
arch/arm/mach-zynq/Makefile | 2 +-
arch/arm/mach-zynq/common.c | 1 +
arch/arm/mach-zynq/common.h | 2 ++
arch/arm/mach-zynq/pm.c | 83 +++++++++++++++++++++++++++++++++++++++++++++
4 files changed, 87 insertions(+), 1 deletion(-)
create mode 100644 arch/arm/mach-zynq/pm.c
diff --git a/arch/arm/mach-zynq/Makefile b/arch/arm/mach-zynq/Makefile
index 1b25d92ebf22..820dff6e1eba 100644
--- a/arch/arm/mach-zynq/Makefile
+++ b/arch/arm/mach-zynq/Makefile
@@ -3,7 +3,7 @@
#
# Common support
-obj-y := common.o slcr.o
+obj-y := common.o slcr.o pm.o
CFLAGS_REMOVE_hotplug.o =-march=armv6k
CFLAGS_hotplug.o =-Wa,-march=armv7-a -mcpu=cortex-a9
obj-$(CONFIG_HOTPLUG_CPU) += hotplug.o
diff --git a/arch/arm/mach-zynq/common.c b/arch/arm/mach-zynq/common.c
index 3cb7c198615a..6bd13e5ce6b7 100644
--- a/arch/arm/mach-zynq/common.c
+++ b/arch/arm/mach-zynq/common.c
@@ -101,6 +101,7 @@ static int __init zynq_get_revision(void)
static void __init zynq_init_late(void)
{
zynq_core_pm_init();
+ zynq_pm_late_init();
}
/**
diff --git a/arch/arm/mach-zynq/common.h b/arch/arm/mach-zynq/common.h
index 596ef0b5067c..0edbb6997b1c 100644
--- a/arch/arm/mach-zynq/common.h
+++ b/arch/arm/mach-zynq/common.h
@@ -40,6 +40,8 @@ extern void __iomem *zynq_scu_base;
/* Hotplug */
extern void zynq_platform_cpu_die(unsigned int cpu);
+void zynq_pm_late_init(void);
+
static inline void zynq_core_pm_init(void)
{
/* A9 clock gating */
diff --git a/arch/arm/mach-zynq/pm.c b/arch/arm/mach-zynq/pm.c
new file mode 100644
index 000000000000..911fcf865be8
--- /dev/null
+++ b/arch/arm/mach-zynq/pm.c
@@ -0,0 +1,83 @@
+/*
+ * Zynq power management
+ *
+ * Copyright (C) 2012 - 2014 Xilinx
+ *
+ * Sören Brinkmann <soren.brinkmann@xxxxxxxxxx>
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <linux/io.h>
+#include <linux/of_address.h>
+#include <linux/of_device.h>
+#include "common.h"
+
+/* register offsets */
+#define DDRC_CTRL_REG1_OFFS 0x60
+#define DDRC_DRAM_PARAM_REG3_OFFS 0x20
+
+/* bitfields */
+#define DDRC_CLOCKSTOP_MASK BIT(23)
+#define DDRC_SELFREFRESH_MASK BIT(12)
+
+static void __iomem *ddrc_base;
+
+/**
+ * zynq_pm_ioremap() - Create IO mappings
+ * @comp: DT compatible string
+ * Return: Pointer to the mapped memory or NULL.
+ *
+ * Remap the memory region for a compatible DT node.
+ */
+static void __iomem *zynq_pm_ioremap(const char *comp)
+{
+ struct device_node *np;
+ void __iomem *base = NULL;
+
+ np = of_find_compatible_node(NULL, NULL, comp);
+ if (np) {
+ base = of_iomap(np, 0);
+ of_node_put(np);
+ } else {
+ pr_warn("%s: no compatible node found for '%s'\n", __func__,
+ comp);
+ }
+
+ return base;
+}
+
+/**
+ * zynq_pm_late_init() - Power management init
+ *
+ * Initialization of power management related featurs and infrastructure.
+ */
+void __init zynq_pm_late_init(void)
+{
+ u32 reg;
+
+ ddrc_base = zynq_pm_ioremap("xlnx,zynq-ddrc-a05");
+ if (!ddrc_base) {
+ pr_warn("%s: Unable to map DDRC IO memory.\n", __func__);
+ } else {
+ /*
+ * Enable DDRC clock stop feature. The HW takes care of
+ * entering/exiting the correct mode depending
+ * on activity state.
+ */
+ reg = readl(ddrc_base + DDRC_DRAM_PARAM_REG3_OFFS);
+ reg |= DDRC_CLOCKSTOP_MASK;
+ writel(reg, ddrc_base + DDRC_DRAM_PARAM_REG3_OFFS);
+ }
+}
--
2.1.0.1.g27b9230
--
To unsubscribe from this list: send the line "unsubscribe devicetree" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
