On Thu, Apr 21, 2016 at 11:45:20AM +0800, Dong Aisheng wrote: > On Fri, Jan 29, 2016 at 02:49:23PM -0800, Stefan Agner wrote: > > If a clock gets enabled early during boot time, it can lead to a PLL > > startup. The wait_lock function makes sure that the PLL is really > > stareted up before it gets used. However, the function sleeps which > > leads to scheduling and an error: > > bad: scheduling from the idle thread! > > ... > > > > Use udelay in case IRQ's are still disabled. > > > > Signed-off-by: Stefan Agner <ste...@agner.ch> > > --- > > drivers/clk/imx/clk-pllv3.c | 5 ++++- > > 1 file changed, 4 insertions(+), 1 deletion(-) > > > > diff --git a/drivers/clk/imx/clk-pllv3.c b/drivers/clk/imx/clk-pllv3.c > > index c05c43d..b5ff561 100644 > > --- a/drivers/clk/imx/clk-pllv3.c > > +++ b/drivers/clk/imx/clk-pllv3.c > > @@ -63,7 +63,10 @@ static int clk_pllv3_wait_lock(struct clk_pllv3 *pll) > > break; > > if (time_after(jiffies, timeout)) > > break; > > - usleep_range(50, 500); > > + if (unlikely(irqs_disabled())) > > This causes a bit confusion that clk_pllv3_prepare is sleepable. > But this line indicates it's possible to be called in irq context. > Although it's only happened during kernel boot phase where irq is > still not enabled. > It seems schedule_debug() somehow did not catch it during early boot > phase. Maybe schedule guys can help explain. > > My question is if it's really worthy to introduce this confusion > to fix the issue since the delay is minor?
I do not understand why it's confusing. The code already obviously indicates this is a special handling for cases where irq is still not enabled, rather than for irq context. The patch is to fix the "bad: scheduling from the idle thread!" warning rather than minimize the delay. Do you have an opinion on how to fix the warning? > Furthermore, shouldn't it be udelay(500)? 500 is for the worst case of sleep, and 50 is good enough for delay. Shawn
