[PATCH v3 2/5] media: atmel-isc: Add prepare and unprepare ops
From: Wenyou Yang <hidden>
Date: 2017-09-28 08:21:27
Also in:
linux-media, lkml
Subsystem:
media input infrastructure (v4l/dvb), the rest · Maintainers:
Mauro Carvalho Chehab, Linus Torvalds
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 <redacted> --- Changes in v3: None Changes in v2: None drivers/media/platform/atmel/atmel-isc-regs.h | 1 + drivers/media/platform/atmel/atmel-isc.c | 30 +++++++++++++++++++++++++++ 2 files changed, 31 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..0b15dc1a3a0b 100644
--- a/drivers/media/platform/atmel/atmel-isc.c
+++ b/drivers/media/platform/atmel/atmel-isc.c@@ -308,6 +308,34 @@ 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) +{ + return isc_wait_clk_stable(hw); +} + +static void isc_clk_unprepare(struct clk_hw *hw) +{ + isc_wait_clk_stable(hw); +} + static int isc_clk_enable(struct clk_hw *hw) { struct isc_clk *isc_clk = to_isc_clk(hw);
@@ -459,6 +487,8 @@ 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