Re: [PATCH 2/3] media: rockchip: Introduce driver for Rockhip's camera interface

Robin Murphy
2020-04-16T12:49:13Z

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;
> +}