Date:   Thu, 16 Apr 2020 13:48:35 +0100
From:   Robin Murphy <robin.murphy@....com>
To:     Maxime Chevallier <maxime.chevallier@...tlin.com>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Heiko Stuebner <heiko@...ech.de>,
        Hans Verkuil <hverkuil-cisco@...all.nl>
Cc:     devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        Paul Kocialkowski <paul.kocialkowski@...tlin.com>,
        linux-rockchip@...ts.infradead.org,
        Thomas Petazzoni <thomas.petazzoni@...tlin.com>,
        Miquel Raynal <miquel.raynal@...tlin.com>,
        linux-arm-kernel@...ts.infradead.org, linux-media@...r.kernel.org
Subject: Re: [PATCH 2/3] media: rockchip: Introduce driver for Rockhip's
 camera interface

Hi Maxime,

Just a handful of drive-by cleanup suggestions to help this smell less 
like a BSP driver...

(one day I still hope to get round to playing with what appears to be 
the DVP interface populated but unused inside my RK3288 box, and the 
camera module I picked up to supposedly fit it, but alas not today)

On 2020-04-03 3:21 pm, Maxime Chevallier wrote:
[...]
> +static int rkcif_plat_probe(struct platform_device *pdev)
> +{
> +	const struct of_device_id *match;
> +	struct device_node *node = pdev->dev.of_node;
> +	struct device *dev = &pdev->dev;
> +	struct v4l2_device *v4l2_dev;
> +	struct rkcif_device *cif_dev;
> +	const struct cif_match_data *data;
> +	struct resource *res;
> +	int i, ret, irq;
> +
> +	match = of_match_node(rkcif_plat_of_match, node);
> +	if (IS_ERR(match))
> +		return PTR_ERR(match);

of_device_get_match_data()

> +
> +	cif_dev = devm_kzalloc(dev, sizeof(*cif_dev), GFP_KERNEL);
> +	if (!cif_dev)
> +		return -ENOMEM;
> +
> +	dev_set_drvdata(dev, cif_dev);
> +	cif_dev->dev = dev;
> +
> +	irq = platform_get_irq(pdev, 0);
> +	if (irq < 0)
> +		return irq;
> +
> +	ret = devm_request_irq(dev, irq, rkcif_irq_handler, IRQF_SHARED,
> +			       dev_driver_string(dev), dev);
> +	if (ret < 0) {
> +		dev_err(dev, "request irq failed: %d\n", ret);
> +		return ret;
> +	}
> +
> +	cif_dev->irq = irq;
> +	data = match->data;
> +	cif_dev->chip_id = data->chip_id;

It pretty much breaks even at the moment, but consider just holding a 
pointer to data itself rather than copying multiple fields into cif_dev, 
particularly if there's any likelihood of adding more in future. The 
couple of places clk_size and chip_id are used here don't really look 
like critical fast-paths where cache/TLB locality is super-important.

> +
> +	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> +	cif_dev->base_addr = devm_ioremap_resource(dev, res);

devm_platform_ioremap_resource()

> +
> +	if (IS_ERR(cif_dev->base_addr))
> +		return PTR_ERR(cif_dev->base_addr);
> +
> +	if (data->clks_num > RKCIF_MAX_BUS_CLK ||
> +		data->rsts_num > RKCIF_MAX_RESET) {

It's silly to have runtime checks of constants - BUILD_BUG_ON() 
somewhere if you really want to validate that the driver data is 
self-consistent.

> +		dev_err(dev, "out of range: clks(%d %d) rsts(%d %d)\n",
> +			data->clks_num, RKCIF_MAX_BUS_CLK,
> +			data->rsts_num, RKCIF_MAX_RESET);
> +		return -EINVAL;
> +	}
> +
> +	for (i = 0; i < data->clks_num; i++) {
> +		struct clk *clk = devm_clk_get(dev, data->clks[i]);
> +
> +		if (IS_ERR(clk)) {
> +			dev_err(dev, "failed to get %s\n", data->clks[i]);
> +			return PTR_ERR(clk);
> +		}
> +
> +		cif_dev->clks[i] = clk;
> +	}

All of the clock handling looks like it could use the clk_bulk_* APIs.

> +
> +	cif_dev->clk_size = data->clks_num;
> +
> +	for (i = 0; i < data->rsts_num; i++) {
> +		struct reset_control *rst =
> +			devm_reset_control_get(dev, data->rsts[i]);
> +		if (IS_ERR(rst)) {
> +			dev_err(dev, "failed to get %s\n", data->rsts[i]);
> +			return PTR_ERR(rst);
> +		}
> +		cif_dev->cif_rst[i] = rst;
> +	}

And possibly the reset_control_array_* APIs for resets? (assuming there 
isn't a subtle ordering requirement implicit in data->rsts)

> +
> +	/* Initialize the stream */
> +	rkcif_stream_init(cif_dev);
> +
> +	strlcpy(cif_dev->media_dev.model, "rkcif",
> +		sizeof(cif_dev->media_dev.model));
> +	cif_dev->media_dev.dev = &pdev->dev;
> +	v4l2_dev = &cif_dev->v4l2_dev;
> +	v4l2_dev->mdev = &cif_dev->media_dev;
> +	strlcpy(v4l2_dev->name, "rkcif", sizeof(v4l2_dev->name));
> +	v4l2_ctrl_handler_init(&cif_dev->ctrl_handler, 8);
> +	v4l2_dev->ctrl_handler = &cif_dev->ctrl_handler;
> +
> +	ret = v4l2_device_register(cif_dev->dev, &cif_dev->v4l2_dev);
> +	if (ret < 0)
> +		return ret;
> +
> +	media_device_init(&cif_dev->media_dev);
> +
> +	ret = media_device_register(&cif_dev->media_dev);
> +	if (ret < 0) {
> +		v4l2_err(v4l2_dev, "Failed to register media device: %d\n",
> +			 ret);
> +		goto err_unreg_v4l2_dev;
> +	}
> +
> +	/* create & register platefom subdev (from of_node) */
> +	ret = rkcif_register_platform_subdevs(cif_dev);
> +	if (ret < 0)
> +		goto err_unreg_media_dev;
> +
> +	ret = of_reserved_mem_device_init(dev);
> +	if (ret)
> +		v4l2_warn(v4l2_dev, "No reserved memory region assign to CIF\n");

It feels like that should probably happen earlier in the "resource 
acquisition" part of probe, before any external init/register calls that 
in principle could want to preallocate DMA buffers.

Also, is the lack of reserved memory really a warn-level condition? The 
DT binding doesn't even appear to treat a "memory-region" property as 
legal, and with CMA or (as appears to be the case for at least RK3288) 
an IOMMU, it should be largely moot anyway.

Robin.

> +
> +	pm_runtime_enable(&pdev->dev);
> +
> +	return 0;
> +
> +err_unreg_media_dev:
> +	media_device_unregister(&cif_dev->media_dev);
> +err_unreg_v4l2_dev:
> +	v4l2_device_unregister(&cif_dev->v4l2_dev);
> +	return ret;
> +}

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