Re: [PATCH] hw_random: omap3-rom-rng: convert timer to delayed work

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On 11/06/2015 12:15 AM, Aaro Koskinen wrote:
We cannot put the HW RNG to idle using a timer because we cannot disable
clocks from atomic context. Use a delayed work instead.

Fixes a warning with CONFIG_DEBUG_MUTEXES on Nokia N900 during boot.

Reported-by: Sebastian Reichel <sre@xxxxxxxxxx>
Signed-off-by: Aaro Koskinen <aaro.koskinen@xxxxxx>
---
  drivers/char/hw_random/omap3-rom-rng.c | 11 ++++++-----
  1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/drivers/char/hw_random/omap3-rom-rng.c b/drivers/char/hw_random/omap3-rom-rng.c
index a405cdc..58191c6 100644
--- a/drivers/char/hw_random/omap3-rom-rng.c
+++ b/drivers/char/hw_random/omap3-rom-rng.c
@@ -29,11 +29,11 @@
  /* param1: ptr, param2: count, param3: flag */
  static u32 (*omap3_rom_rng_call)(u32, u32, u32);

-static struct timer_list idle_timer;
+static struct delayed_work idle_work;
  static int rng_idle;
  static struct clk *rng_clk;

-static void omap3_rom_rng_idle(unsigned long data)
+static void omap3_rom_rng_idle(struct work_struct *work)
  {
  	int r;

@@ -51,7 +51,7 @@ static int omap3_rom_rng_get_random(void *buf, unsigned int count)
  	u32 r;
  	u32 ptr;

-	del_timer_sync(&idle_timer);
+	cancel_delayed_work_sync(&idle_work);
  	if (rng_idle) {
  		clk_prepare_enable(rng_clk);
  		r = omap3_rom_rng_call(0, 0, RNG_GEN_PRNG_HW_INIT);
@@ -65,7 +65,7 @@ static int omap3_rom_rng_get_random(void *buf, unsigned int count)

  	ptr = virt_to_phys(buf);
  	r = omap3_rom_rng_call(ptr, count, RNG_GEN_HW);
-	mod_timer(&idle_timer, jiffies + msecs_to_jiffies(500));
+	schedule_delayed_work(&idle_work, msecs_to_jiffies(500));
  	if (r != 0)
  		return -EINVAL;
  	return 0;
@@ -102,7 +102,7 @@ static int omap3_rom_rng_probe(struct platform_device *pdev)
  		return -EINVAL;
  	}

-	setup_timer(&idle_timer, omap3_rom_rng_idle, 0);
+	INIT_DELAYED_WORK(&idle_work, omap3_rom_rng_idle);
  	rng_clk = devm_clk_get(&pdev->dev, "ick");
  	if (IS_ERR(rng_clk)) {
  		pr_err("unable to get RNG clock\n");
@@ -118,6 +118,7 @@ static int omap3_rom_rng_probe(struct platform_device *pdev)

  static int omap3_rom_rng_remove(struct platform_device *pdev)
  {
+	cancel_delayed_work_sync(&idle_work);
  	hwrng_unregister(&omap3_rom_rng_ops);
  	clk_disable_unprepare(rng_clk);
  	return 0;


Sry, It looks like PM runtime autosuspend might work well here.
What do you think?

--
regards,
-grygorii
--
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