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Subject[PATCH v5 2/5] media: atmel-isc: Add prepare and unprepare ops
Date
A software write operation to the ISC_CLKEN or ISC_CLKDIS register
requires double clock domain synchronization and is not permitted
when the ISC_SR.SIP is asserted. So add the .prepare and .unprepare
ops to make sure the ISC_CLKSR.SIP is unasserted before the write
operation to the ISC_CLKEN or ISC_CLKDIS register.

Signed-off-by: Wenyou Yang <wenyou.yang@microchip.com>
---

Changes in v5:
- Fix the clock ID which enters the runtime suspend should be
ISC_ISPCK, instead of ISC_MCK for clk_prepare/clk_unprepare().

Changes in v4:
- Call pm_runtime_get_sync() and pm_runtime_put_sync() in ->prepare
and ->unprepare callback.

Changes in v3: None
Changes in v2: None

drivers/media/platform/atmel/atmel-isc-regs.h | 1 +
drivers/media/platform/atmel/atmel-isc.c | 40 +++++++++++++++++++++++++++
2 files changed, 41 insertions(+)

diff --git a/drivers/media/platform/atmel/atmel-isc-regs.h b/drivers/media/platform/atmel/atmel-isc-regs.h
index 6936ac467609..93e58fcf1d5f 100644
--- a/drivers/media/platform/atmel/atmel-isc-regs.h
+++ b/drivers/media/platform/atmel/atmel-isc-regs.h
@@ -42,6 +42,7 @@

/* ISC Clock Status Register */
#define ISC_CLKSR 0x00000020
+#define ISC_CLKSR_SIP BIT(31)

#define ISC_CLK(n) BIT(n)

diff --git a/drivers/media/platform/atmel/atmel-isc.c b/drivers/media/platform/atmel/atmel-isc.c
index 991f962b7023..329ee8f256bb 100644
--- a/drivers/media/platform/atmel/atmel-isc.c
+++ b/drivers/media/platform/atmel/atmel-isc.c
@@ -308,6 +308,44 @@ module_param(sensor_preferred, uint, 0644);
MODULE_PARM_DESC(sensor_preferred,
"Sensor is preferred to output the specified format (1-on 0-off), default 1");

+static int isc_wait_clk_stable(struct clk_hw *hw)
+{
+ struct isc_clk *isc_clk = to_isc_clk(hw);
+ struct regmap *regmap = isc_clk->regmap;
+ unsigned long timeout = jiffies + usecs_to_jiffies(1000);
+ unsigned int status;
+
+ while (time_before(jiffies, timeout)) {
+ regmap_read(regmap, ISC_CLKSR, &status);
+ if (!(status & ISC_CLKSR_SIP))
+ return 0;
+
+ usleep_range(10, 250);
+ }
+
+ return -ETIMEDOUT;
+}
+
+static int isc_clk_prepare(struct clk_hw *hw)
+{
+ struct isc_clk *isc_clk = to_isc_clk(hw);
+
+ if (isc_clk->id == ISC_ISPCK)
+ pm_runtime_get_sync(isc_clk->dev);
+
+ return isc_wait_clk_stable(hw);
+}
+
+static void isc_clk_unprepare(struct clk_hw *hw)
+{
+ struct isc_clk *isc_clk = to_isc_clk(hw);
+
+ isc_wait_clk_stable(hw);
+
+ if (isc_clk->id == ISC_ISPCK)
+ pm_runtime_put_sync(isc_clk->dev);
+}
+
static int isc_clk_enable(struct clk_hw *hw)
{
struct isc_clk *isc_clk = to_isc_clk(hw);
@@ -459,6 +497,8 @@ static int isc_clk_set_rate(struct clk_hw *hw,
}

static const struct clk_ops isc_clk_ops = {
+ .prepare = isc_clk_prepare,
+ .unprepare = isc_clk_unprepare,
.enable = isc_clk_enable,
.disable = isc_clk_disable,
.is_enabled = isc_clk_is_enabled,
--
2.13.0
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