linux-kernel - Re: [PATCH v6 4/8] media: platform: Add Cedrus VPU decoder driver

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Message-ID: <faa0436aad809ca562b5c152420b1e4d4b6f507b.camel@collabora.com>
Date:   Fri, 03 Aug 2018 17:49:38 -0300
From:   Ezequiel Garcia <ezequiel@...labora.com>
To:     Paul Kocialkowski <paul.kocialkowski@...tlin.com>,
        linux-media@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        devel@...verdev.osuosl.org
Cc:     Mauro Carvalho Chehab <mchehab@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Maxime Ripard <maxime.ripard@...tlin.com>,
        Chen-Yu Tsai <wens@...e.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Thomas Petazzoni <thomas.petazzoni@...tlin.com>,
        linux-sunxi@...glegroups.com,
        Hugues Fruchet <hugues.fruchet@...com>,
        Randy Li <ayaka@...lik.info>,
        Hans Verkuil <hverkuil@...all.nl>,
        Tomasz Figa <tfiga@...omium.org>,
        Alexandre Courbot <acourbot@...omium.org>,
        Philipp Zabel <p.zabel@...gutronix.de>,
        Laurent Pinchart <laurent.pinchart@...asonboard.com>,
        Sakari Ailus <sakari.ailus@...ux.intel.com>
Subject: Re: [PATCH v6 4/8] media: platform: Add Cedrus VPU decoder driver

On Wed, 2018-07-25 at 12:02 +0200, Paul Kocialkowski wrote:
> This introduces the Cedrus VPU driver that supports the VPU found in
> Allwinner SoCs, also known as Video Engine. It is implemented through
> a v4l2 m2m decoder device and a media device (used for media requests).
> So far, it only supports MPEG2 decoding.
> 
> Since this VPU is stateless, synchronization with media requests is
> required in order to ensure consistency between frame headers that
> contain metadata about the frame to process and the raw slice data that
> is used to generate the frame.
> 
> This driver was made possible thanks to the long-standing effort
> carried out by the linux-sunxi community in the interest of reverse
> engineering, documenting and implementing support for Allwinner VPU.
> 
> Signed-off-by: Paul Kocialkowski <paul.kocialkowski@...tlin.com>
[..]
> +static int cedrus_probe(struct platform_device *pdev)
> +{
> +	struct cedrus_dev *dev;
> +	struct video_device *vfd;
> +	int ret;
> +
> +	dev = devm_kzalloc(&pdev->dev, sizeof(*dev), GFP_KERNEL);
> +	if (!dev)
> +		return -ENOMEM;
> +
> +	dev->dev = &pdev->dev;
> +	dev->pdev = pdev;
> +
> +	ret = cedrus_hw_probe(dev);
> +	if (ret) {
> +		dev_err(&pdev->dev, "Failed to probe hardware\n");
> +		return ret;
> +	}
> +
> +	dev->dec_ops[CEDRUS_CODEC_MPEG2] = &cedrus_dec_ops_mpeg2;
> +
> +	mutex_init(&dev->dev_mutex);
> +	spin_lock_init(&dev->irq_lock);
> +

A minor thing.

I believe this spinlock is not needed. All the data structures
it's accessing are already protected, and some operations
(stop_streaming) are guaranteed to not run at the same
time as a job.

Regards,
Eze