linux-kernel - Re: [RFC PATCH v1 3/5] media: tegra-video: Move PM runtime handle to streaming

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Date:   Tue, 28 Apr 2020 16:59:30 +0300
From:   Dmitry Osipenko <digetx@...il.com>
To:     Sowjanya Komatineni <skomatineni@...dia.com>,
        thierry.reding@...il.com, jonathanh@...dia.com, frankc@...dia.com,
        hverkuil@...all.nl
Cc:     linux-media@...r.kernel.org, linux-tegra@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH v1 3/5] media: tegra-video: Move PM runtime handle to
 streaming

28.04.2020 07:20, Sowjanya Komatineni пишет:
> diff --git a/drivers/staging/media/tegra-video/csi.c b/drivers/staging/media/tegra-video/csi.c
> index b3dd0c3..29ccdae 100644
> --- a/drivers/staging/media/tegra-video/csi.c
> +++ b/drivers/staging/media/tegra-video/csi.c
> @@ -272,8 +272,25 @@ static int tegra_csi_s_stream(struct v4l2_subdev *subdev, int enable)
>  	struct tegra_vi_channel *chan = v4l2_get_subdev_hostdata(subdev);
>  	struct tegra_csi_channel *csi_chan = to_csi_chan(subdev);
>  	struct tegra_csi *csi = csi_chan->csi;
> +	int ret;
> +
> +	if (enable && atomic_add_return(1, &csi->clk_refcnt) == 1) {
> +		ret = pm_runtime_get_sync(csi->dev);
> +		if (ret < 0) {
> +			dev_err(csi->dev,
> +				"failed to get runtime PM: %d\n", ret);
> +			pm_runtime_put_noidle(csi->dev);
> +			atomic_dec(&csi->clk_refcnt);
> +			return ret;
> +		}
> +	}
> +
> +	ret = csi->ops->csi_streaming(csi_chan, chan->pg_mode, enable);
>  
> -	return csi->ops->csi_streaming(csi_chan, chan->pg_mode, enable);
> +	if ((ret < 0 || !enable) && atomic_dec_and_test(&csi->clk_refcnt))
> +		pm_runtime_put_sync(csi->dev);

Runtime PM maintains its own refcount, why these
clk_refcnt/power_on_refcnt are needed?