Messages in this thread | | | Date | Tue, 15 Jan 2013 09:59:53 +0100 | Subject | Re: [PATCH 04/18] power: ab8500_fg: Replace msleep() with usleep_range() for greater accuracy | From | Linus Walleij <> |
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On Tue, Jan 15, 2013 at 9:48 AM, Lee Jones <lee.jones@linaro.org> wrote: > On Mon, 14 Jan 2013, Joe Perches wrote:
>> > - msleep(5); >> > + usleep_range(5000, 5001); >> >> If you're going to give a range that small >> you might as well use usleep instead. >> >> Otherwise, add some tolerance to allow any >> other coalesced wakeup to occur. > > I can't increase the tolerance, as I don't know how that would > effect the running of the system, and the person who would know > is off on parental leave. > > What I can tell you is we're only using usleep_range() because > there is no usleep in the kernel. At least that's what we've > been led to believe: > > Documentation/timers/timers-howto.txt: > > - Why is there no "usleep" / What is a good range? > Since usleep_range is built on top of hrtimers, the > wakeup will be very precise (ish), thus a simple > usleep function would likely introduce a large number > of undesired interrupts.
And I think the above is why we have this in the kernel: arch/arm/mach-davinci/board-da850-evm.c: usleep_range(1000, 1000); arch/arm/mach-tegra/pcie.c: usleep_range(1000, 1000); drivers/clk/clk-wm831x.c: usleep_range(2000, 2000); drivers/media/i2c/m5mols/m5mols_core.c: usleep_range(200, 200); drivers/media/i2c/s5k6aa.c: usleep_range(4000, 4000); drivers/media/i2c/smiapp/smiapp-core.c: usleep_range(1000, 1000); drivers/net/ethernet/broadcom/bnx2x/bnx2x_main.c: usleep_range(1000, 1000);
There are quite a few of these.
Let's ping John Stultz for some clarification ...
Yours, Linus Walleij
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