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    SubjectRe: [PATCH] Exynos : Add support for Exynos random number generator
    On Tue, 26 Jun 2012, Stephen Boyd wrote:

    > On 06/21/12 18:39, jonghwa3.lee@samsung.com wrote:
    > > On 2012년 06월 21일 12:12, Stephen Boyd wrote:
    > >
    > >> On 06/20/12 19:39, jonghwa3.lee@samsung.com wrote:
    > >>>>> +static int exynos_init(struct hwrng *rng)
    > >>>>> +{
    > >>>>> + struct exynos_rng *exynos_rng = container_of(rng,
    > >>>>> + struct exynos_rng, rng);
    > >>>>> + int i;
    > >>>>> + int ret = 0;
    > >>>>> + u32 PRND_SEED[5];
    > >>>>> +
    > >>>>> + pm_runtime_put_noidle(exynos_rng->dev);
    > >>>>> + pm_runtime_get_sync(exynos_rng->dev);
    > >>>> This looks very odd. Why are you calling pm_runtime_put_noidle()?
    > >>>>
    > >>> When this callback function is called, the status of power state is
    > >>> 'suspended' and use_count is 1.

    That's strange to begin with. If the usage counter is > 0 then the
    device shouldn't be suspended. How does this happen?

    > To perform pm_runtime_get_sync()
    > >>> correctly, it requires to have 'suspended' status and use_count is 0.

    That's not true. pm_runtime_get_sync works perfectly well when the
    status is "suspended" and the usage counter is > 0.

    > >>> Thus i force to decrease use_count only with using
    > >>> pm_runtime_put_noidle. I know it looks odd, but i couldn't find better
    > >>> way. Otherwise it can use clk_enable() directly, but i think that it
    > >>> isn't good neither.
    > >> Is the device suspended initially at probe? If so can you set the state
    > >> of the device to suspended?
    > >>
    > >
    > > Yes, it suspended already at the initial of probing. But i can't get
    > > your point, you want to me to make device suspended?
    >
    > I mean to say you should probably call pm_runtime_set_suspended() during
    > probe. But I'm not sure and I would defer to people more familiar with
    > runtime pm.

    If the device starts out in a suspended state then the subsystem or
    driver should call pm_runtime_set_suspended before calling
    pm_runtime_enable.

    Alan Stern

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