[PATCHv3 08/16] clk: mvebu: add suspend/resume for gatable clocks

From: Thomas Petazzoni
Date: Fri Nov 21 2014 - 11:00:38 EST

This commit adds suspend/resume support for the gatable clock driver
used on Marvell EBU platforms. When getting out of suspend, the
Marvell EBU platforms go through the bootloader, which re-enables all
gatable clocks. However, upon resume, the clock framework will not
disable again all gatable clocks that are not used.

Therefore, if the clock driver does not save/restore the state of the
gatable clocks, all gatable clocks that are not claimed by any device
driver will remain enabled after a resume. This is why this driver
saves and restores the state of those clocks.

Since clocks aren't real devices, we don't have the normal ->suspend()
and ->resume() of the device model, and have to use the ->suspend()
and ->resume() hooks of the syscore_ops mechanism. This mechanism has
the unfortunate idea of not providing a way of passing private data,
which requires us to change the driver to make the assumption that
there is only once instance of the gatable clock control structure.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@xxxxxxxxxxxxxxxxxx>
Cc: Mike Turquette <mturquette@xxxxxxxxxx>
Cc: linux-kernel@xxxxxxxxxxxxxxx
Acked-by: Gregory CLEMENT <gregory.clement@xxxxxxxxxxxxxxxxxx>
drivers/clk/mvebu/common.c | 32 ++++++++++++++++++++++++++++++--
1 file changed, 30 insertions(+), 2 deletions(-)

diff --git a/drivers/clk/mvebu/common.c b/drivers/clk/mvebu/common.c
index b7fcb46..0d4d121 100644
--- a/drivers/clk/mvebu/common.c
+++ b/drivers/clk/mvebu/common.c
@@ -19,6 +19,7 @@
#include <linux/io.h>
#include <linux/of.h>
#include <linux/of_address.h>
+#include <linux/syscore_ops.h>

#include "common.h"

@@ -177,14 +178,17 @@ struct clk_gating_ctrl {
spinlock_t *lock;
struct clk **gates;
int num_gates;
+ void __iomem *base;
+ u32 saved_reg;

#define to_clk_gate(_hw) container_of(_hw, struct clk_gate, hw)

+static struct clk_gating_ctrl *ctrl;
static struct clk *clk_gating_get_src(
struct of_phandle_args *clkspec, void *data)
- struct clk_gating_ctrl *ctrl = (struct clk_gating_ctrl *)data;
int n;

if (clkspec->args_count < 1)
@@ -199,15 +203,35 @@ static struct clk *clk_gating_get_src(
return ERR_PTR(-ENODEV);

+static int mvebu_clk_gating_suspend(void)
+ ctrl->saved_reg = readl(ctrl->base);
+ return 0;
+static void mvebu_clk_gating_resume(void)
+ writel(ctrl->saved_reg, ctrl->base);
+static struct syscore_ops clk_gate_syscore_ops = {
+ .suspend = mvebu_clk_gating_suspend,
+ .resume = mvebu_clk_gating_resume,
void __init mvebu_clk_gating_setup(struct device_node *np,
const struct clk_gating_soc_desc *desc)
- struct clk_gating_ctrl *ctrl;
struct clk *clk;
void __iomem *base;
const char *default_parent = NULL;
int n;

+ if (ctrl) {
+ pr_err("mvebu-clk-gating: cannot instantiate more than one gatable clock device\n");
+ return;
+ }
base = of_iomap(np, 0);
if (WARN_ON(!base))
@@ -225,6 +249,8 @@ void __init mvebu_clk_gating_setup(struct device_node *np,
/* lock must already be initialized */
ctrl->lock = &ctrl_gating_lock;

+ ctrl->base = base;
/* Count, allocate, and register clock gates */
for (n = 0; desc[n].name;)
@@ -246,6 +272,8 @@ void __init mvebu_clk_gating_setup(struct device_node *np,

of_clk_add_provider(np, clk_gating_get_src, ctrl);

+ register_syscore_ops(&clk_gate_syscore_ops);

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