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Message-ID: <20210428084431.0c2d505b@coco.lan>
Date: Wed, 28 Apr 2021 08:44:31 +0200
From: Mauro Carvalho Chehab <mchehab+huawei@...nel.org>
To: Ezequiel Garcia <ezequiel@...labora.com>
Cc: Robin Murphy <robin.murphy@....com>, linuxarm@...wei.com,
mauro.chehab@...wei.com,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
Mauro Carvalho Chehab <mchehab@...nel.org>,
Philipp Zabel <p.zabel@...gutronix.de>,
devel@...verdev.osuosl.org, linux-kernel@...r.kernel.org,
linux-media@...r.kernel.org, linux-rockchip@...ts.infradead.org
Subject: Re: [PATCH v3 79/79] media: hantro: document the usage of
pm_runtime_get_sync()
Em Wed, 28 Apr 2021 08:27:42 +0200
Mauro Carvalho Chehab <mchehab+huawei@...nel.org> escreveu:
> Em Tue, 27 Apr 2021 12:18:32 -0300
> Ezequiel Garcia <ezequiel@...labora.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+huawei@...nel.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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