lkml.org 
[lkml]   [2021]   [Apr]   [27]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    SubjectRe: [PATCH v3 79/79] media: hantro: document the usage of pm_runtime_get_sync()
    From
    Date
    On 2021-04-27 11:27, Mauro Carvalho Chehab wrote:
    > Despite other *_get()/*_put() functions, where usage count is
    > incremented only if not errors, the pm_runtime_get_sync() has
    > a different behavior, incrementing the counter *even* on
    > errors.
    >
    > That's an error prone behavior, as people often forget to
    > decrement the usage counter.
    >
    > However, the hantro driver depends on this behavior, as it
    > will decrement the usage_count unconditionally at the m2m
    > job finish time, which makes sense.
    >
    > So, intead of using the pm_runtime_resume_and_get() that
    > would decrement the counter on error, keep the current
    > API, but add a documentation explaining the rationale for
    > keep using pm_runtime_get_sync().
    >
    > Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
    > ---
    > drivers/staging/media/hantro/hantro_drv.c | 7 +++++++
    > 1 file changed, 7 insertions(+)
    >
    > diff --git a/drivers/staging/media/hantro/hantro_drv.c b/drivers/staging/media/hantro/hantro_drv.c
    > index 595e82a82728..96f940c1c85c 100644
    > --- a/drivers/staging/media/hantro/hantro_drv.c
    > +++ b/drivers/staging/media/hantro/hantro_drv.c
    > @@ -155,6 +155,13 @@ static void device_run(void *priv)
    > ret = clk_bulk_enable(ctx->dev->variant->num_clocks, ctx->dev->clocks);
    > if (ret)
    > goto err_cancel_job;

    ..except this can also cause the same pm_runtime_put_autosuspend() call
    without even reaching the "matching" get below, so rather than some kind
    of cleverness it seems more like it's just broken :/

    Robin.

    > +
    > + /*
    > + * The pm_runtime_get_sync() will increment dev->power.usage_count,
    > + * even on errors. That's the expected behavior here, since the
    > + * hantro_job_finish() function at the error handling code
    > + * will internally call pm_runtime_put_autosuspend().
    > + */
    > ret = pm_runtime_get_sync(ctx->dev->dev);
    > if (ret < 0)
    > goto err_cancel_job;
    >

    \
     
     \ /
      Last update: 2021-04-27 17:09    [W:5.941 / U:0.012 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site