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Message-ID: <20200626074818.GD3109062@ulmo>
Date: Fri, 26 Jun 2020 09:48:18 +0200
From: Thierry Reding <thierry.reding@...il.com>
To: Dmitry Osipenko <digetx@...il.com>
Cc: Jonathan Hunter <jonathanh@...dia.com>,
Mauro Carvalho Chehab <mchehab@...nel.org>,
Hans Verkuil <hverkuil@...all.nl>, linux-media@...r.kernel.org,
linux-tegra@...r.kernel.org, devel@...verdev.osuosl.org,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 4/4] media: staging: tegra-vde: Power-cycle hardware
on probe
On Wed, Jun 24, 2020 at 06:08:47PM +0300, Dmitry Osipenko wrote:
> VDE partition is left turned ON after bootloader on most devices, hence
> let's ensure that it's turned OFF in order to lower power leakage while
> hardware is idling by turning it ON and OFF during of the driver's probe.
>
> Signed-off-by: Dmitry Osipenko <digetx@...il.com>
> ---
> drivers/staging/media/tegra-vde/vde.c | 8 ++++++++
> 1 file changed, 8 insertions(+)
>
> diff --git a/drivers/staging/media/tegra-vde/vde.c b/drivers/staging/media/tegra-vde/vde.c
> index b64e35b86fb4..3be96c36bf43 100644
> --- a/drivers/staging/media/tegra-vde/vde.c
> +++ b/drivers/staging/media/tegra-vde/vde.c
> @@ -1068,6 +1068,14 @@ static int tegra_vde_probe(struct platform_device *pdev)
> pm_runtime_use_autosuspend(dev);
> pm_runtime_set_autosuspend_delay(dev, 300);
>
> + /*
> + * VDE partition may be left ON after bootloader, hence let's
> + * power-cycle it in order to put hardware into a predictable lower
> + * power state.
> + */
> + pm_runtime_get_sync(dev);
> + pm_runtime_put(dev);
> +
> return 0;
>
> err_deinit_iommu:
Shouldn't this happen automatically? My understanding is that power
domains are turned on automatically before ->probe() and then unless a
runtime PM reference is taken during ->probe() it will get turned off
again after ->probe()?
Is that not happening? Is auto-suspend perhaps getting in the way
somehow?
Thierry
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