Re: [PATCH v2 4/4] media: staging: tegra-vde: Power-cycle hardware on probe

[Thierry Reding <thierry.reding@gmail.com>]

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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@gmail.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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