Em Wed, 28 Apr 2021 08:27:42 +0200
Mauro Carvalho Chehab <mchehab+hua...@kernel.org> escreveu:

> Em Tue, 27 Apr 2021 12:18:32 -0300
> Ezequiel Garcia <ezequ...@collabora.com> escreveu:
> 
> > On Tue, 2021-04-27 at 16:08 +0100, Robin Murphy wrote:  
> > > 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+hua...@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 :/
> > >     
> > 
> > Indeed, I was trying to find time to cook a quick patch, but kept
> > getting preempted.
> > 
> > Feel free to submit a fix for this, otherwise, I'll try to find
> > time later this week.  
> 
> What about doing this instead:
> 
> diff --git a/drivers/staging/media/hantro/hantro_drv.c 
> b/drivers/staging/media/hantro/hantro_drv.c
> index 595e82a82728..67de6b15236d 100644
> --- a/drivers/staging/media/hantro/hantro_drv.c
> +++ b/drivers/staging/media/hantro/hantro_drv.c
> @@ -56,14 +56,12 @@ dma_addr_t hantro_get_ref(struct hantro_ctx *ctx, u64 ts)
>       return hantro_get_dec_buf_addr(ctx, buf);
>  }
>  
> -static void hantro_job_finish(struct hantro_dev *vpu,
> -                           struct hantro_ctx *ctx,
> -                           enum vb2_buffer_state result)
> +static void hantro_job_finish_no_pm(struct hantro_dev *vpu,
> +                                 struct hantro_ctx *ctx,
> +                                 enum vb2_buffer_state result)
>  {
>       struct vb2_v4l2_buffer *src, *dst;
>  
> -     pm_runtime_mark_last_busy(vpu->dev);
> -     pm_runtime_put_autosuspend(vpu->dev);
>       clk_bulk_disable(vpu->variant->num_clocks, vpu->clocks);
>  
>       src = v4l2_m2m_next_src_buf(ctx->fh.m2m_ctx);
> @@ -81,6 +79,16 @@ static void hantro_job_finish(struct hantro_dev *vpu,
>                                        result);
>  }
>  
> +static void hantro_job_finish(struct hantro_dev *vpu,
> +                           struct hantro_ctx *ctx,
> +                           enum vb2_buffer_state result)
> +{
> +     pm_runtime_mark_last_busy(vpu->dev);
> +     pm_runtime_put_autosuspend(vpu->dev);
> +
> +     hantro_job_finish_no_pm(vpu, ctx, result);
> +}
> +
>  void hantro_irq_done(struct hantro_dev *vpu,
>                    enum vb2_buffer_state result)
>  {
> @@ -152,12 +160,13 @@ static void device_run(void *priv)
>       src = hantro_get_src_buf(ctx);
>       dst = hantro_get_dst_buf(ctx);
>  
> +     ret = pm_runtime_resume_and_get(ctx->dev->dev);
> +     if (ret < 0)
> +             goto err_cancel_job;
> +
>       ret = clk_bulk_enable(ctx->dev->variant->num_clocks, ctx->dev->clocks);
>       if (ret)
>               goto err_cancel_job;
> -     ret = pm_runtime_get_sync(ctx->dev->dev);
> -     if (ret < 0)
> -             goto err_cancel_job;
>  
>       v4l2_m2m_buf_copy_metadata(src, dst, true);
>  
> @@ -165,7 +174,7 @@ static void device_run(void *priv)
>       return;
>  
>  err_cancel_job:
> -     hantro_job_finish(ctx->dev, ctx, VB2_BUF_STATE_ERROR);
> +     hantro_job_finish_no_pm(ctx->dev, ctx, VB2_BUF_STATE_ERROR);
>  }
>  
>  static struct v4l2_m2m_ops vpu_m2m_ops = {
> 
> Thanks,
> Mauro

Actually, the order at the finish logic should change as well.
Maybe like this:

<snip>
static void hantro_job_finish_no_pm(struct hantro_dev *vpu,
                                    struct hantro_ctx *ctx,
                                    enum vb2_buffer_state result)
{
        struct vb2_v4l2_buffer *src, *dst;

        src = v4l2_m2m_next_src_buf(ctx->fh.m2m_ctx);
        dst = v4l2_m2m_next_dst_buf(ctx->fh.m2m_ctx);

        if (WARN_ON(!src))
                return;
        if (WARN_ON(!dst))
                return;

        src->sequence = ctx->sequence_out++;
        dst->sequence = ctx->sequence_cap++;

        v4l2_m2m_buf_done_and_job_finish(ctx->dev->m2m_dev, ctx->fh.m2m_ctx,
                                         result);
}

static void hantro_job_finish(struct hantro_dev *vpu,
                              struct hantro_ctx *ctx,
                              enum vb2_buffer_state result)
{

        hantro_job_finish_no_pm(vpu, ctx, result);

        clk_bulk_disable(vpu->variant->num_clocks, vpu->clocks);

        pm_runtime_mark_last_busy(vpu->dev);
        pm_runtime_put_autosuspend(vpu->dev);
}

static void device_run(void *priv)
{
        struct hantro_ctx *ctx = priv;
        struct vb2_v4l2_buffer *src, *dst;
        int ret;

        src = hantro_get_src_buf(ctx);
        dst = hantro_get_dst_buf(ctx);

        ret = pm_runtime_resume_and_get(ctx->dev->dev);
        if (ret < 0)
                goto err_cancel_job;

        ret = clk_bulk_enable(ctx->dev->variant->num_clocks, ctx->dev->clocks);
        if (ret)
                goto err_cancel_job;

        v4l2_m2m_buf_copy_metadata(src, dst, true);

        ctx->codec_ops->run(ctx);
        return;

err_cancel_job:
        hantro_job_finish_no_pm(ctx->dev, ctx, VB2_BUF_STATE_ERROR);
}
</snip>


Thanks,
Mauro
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