RE: [PATCH v11 2/2] media: v4l: xilinx: Add Xilinx MIPI CSI-2 Rx Subsystem driver

[Vishal Sagar <vsagar@xilinx.com>]

Hi Luca,

Thanks for going through the patch and providing your feedback.

> -----Original Message-----
> From: Luca Ceresoli <luca@lucaceresoli.net>
> Sent: Tuesday, April 21, 2020 4:00 PM
> To: Vishal Sagar <vsagar@xilinx.com>; Hyun Kwon <hyunk@xilinx.com>;
> laurent.pinchart@ideasonboard.com; mchehab@kernel.org;
> robh+dt@kernel.org; mark.rutland@arm.com; Michal Simek
> <michals@xilinx.com>; linux-media@vger.kernel.org;
> devicetree@vger.kernel.org; hans.verkuil@cisco.com; linux-arm-
> kernel@lists.infradead.org; linux-kernel@vger.kernel.org; Dinesh Kumar
> <dineshk@xilinx.com>; Sandip Kothari <sandipk@xilinx.com>; Jacopo Mondi
> <jacopo@jmondi.org>
> Cc: Hyun Kwon <hyunk@xilinx.com>
> Subject: Re: [PATCH v11 2/2] media: v4l: xilinx: Add Xilinx MIPI CSI-2 Rx
> Subsystem driver
> 
> Hi Vishal,
> 
> thanks for having resumed this patchset!
> 
> On 09/04/20 21:44, Vishal Sagar wrote:
> [...]
> > +static int xcsi2rxss_parse_of(struct xcsi2rxss_state *xcsi2rxss) {
> > +	struct xcsi2rxss_core *core = &xcsi2rxss->core;
> > +	struct device_node *node = xcsi2rxss->core.dev->of_node;
> 
> Can be simplified as:
> 
> 	struct device_node *node = core.dev->of_node;
> 

Got it. Will update in next version.
struct device_node *node = core->dev->of_node

> > +	unsigned int nports, irq;
> > +	bool en_csi_v20, vfb;
> > +	int ret;
> > +
> > +	en_csi_v20 = of_property_read_bool(node, "xlnx,en-csi-v2-0");
> > +	if (en_csi_v20)
> > +		core->en_vcx = of_property_read_bool(node, "xlnx,en-vcx");
> > +
> > +	core->enable_active_lanes =
> > +		of_property_read_bool(node, "xlnx,en-active-lanes");
> > +
> > +	ret = of_property_read_u32(node, "xlnx,csi-pxl-format",
> > +				   &core->datatype);
> > +	if (ret < 0) {
> > +		dev_err(core->dev, "missing xlnx,csi-pxl-format property\n");
> > +		return ret;
> > +	}
> > +
> > +	switch (core->datatype) {
> > +	case XCSI_DT_YUV4228B:
> > +	case XCSI_DT_RGB444:
> > +	case XCSI_DT_RGB555:
> > +	case XCSI_DT_RGB565:
> > +	case XCSI_DT_RGB666:
> > +	case XCSI_DT_RGB888:
> > +	case XCSI_DT_RAW6:
> > +	case XCSI_DT_RAW7:
> > +	case XCSI_DT_RAW8:
> > +	case XCSI_DT_RAW10:
> > +	case XCSI_DT_RAW12:
> > +	case XCSI_DT_RAW14:
> > +		break;
> > +	case XCSI_DT_YUV42210B:
> > +	case XCSI_DT_RAW16:
> > +	case XCSI_DT_RAW20:
> > +		if (!en_csi_v20) {
> > +			ret = -EINVAL;
> > +			dev_dbg(core->dev, "enable csi v2 for this pixel
> format");
> > +		}
> > +		break;
> > +	default:
> > +		ret = -EINVAL;
> > +	}
> > +	if (ret < 0) {
> > +		dev_err(core->dev, "invalid csi-pxl-format property!\n");
> > +		return ret;
> > +	}
> > +
> > +	vfb = of_property_read_bool(node, "xlnx,vfb");
> > +	if (!vfb) {
> > +		dev_err(core->dev, "failed as VFB is disabled!\n");
> > +		return -EINVAL;
> > +	}
> > +
> > +	for (nports = 0; nports < XCSI_MEDIA_PADS; nports++) {
> > +		struct fwnode_handle *ep;
> > +		struct v4l2_fwnode_endpoint vep = {
> > +			.bus_type = V4L2_MBUS_CSI2_DPHY
> > +		};
> > +
> > +		ep = fwnode_graph_get_endpoint_by_id(dev_fwnode(core-
> >dev),
> > +						     nports, 0,
> > +
> FWNODE_GRAPH_ENDPOINT_NEXT);
> > +		if (!ep)
> > +			break;
> > +		/*
> > +		 * since first port is sink port and it contains
> > +		 * all info about data-lanes and cfa-pattern,
> > +		 * don't parse second port but only check if exists
> > +		 */
> > +		if (nports == XVIP_PAD_SOURCE) {
> > +			dev_dbg(core->dev, "no need to parse source port");
> > +			fwnode_handle_put(ep);
> > +			continue;
> > +		}
> > +
> > +		ret = v4l2_fwnode_endpoint_parse(ep, &vep);
> > +		if (ret) {
> > +			dev_err(core->dev, "error parsing sink port");
> > +			fwnode_handle_put(ep);
> > +			return ret;
> > +		}
> > +
> > +		dev_dbg(core->dev, "port %d bus type = %d\n", nports,
> > +			vep.bus_type);
> > +
> > +		if (vep.bus_type == V4L2_MBUS_CSI2_DPHY) {
> > +			dev_dbg(core->dev, "base.port = %d base.id = %d\n",
> > +				vep.base.port, vep.base.id);
> > +
> > +			dev_dbg(core->dev, "mipi number lanes = %d\n",
> > +				vep.bus.mipi_csi2.num_data_lanes);
> > +
> > +			core->max_num_lanes =
> > +				vep.bus.mipi_csi2.num_data_lanes;
> > +		}
> > +		fwnode_handle_put(ep);
> > +	}
> > +
> > +	if (nports != XCSI_MEDIA_PADS) {
> > +		dev_err(core->dev, "invalid number of ports %u\n", nports);
> > +		return -EINVAL;
> > +	}
> > +
> > +	/* Register interrupt handler */
> > +	irq = irq_of_parse_and_map(node, 0);
> > +	ret = devm_request_irq(core->dev, irq, xcsi2rxss_irq_handler,
> > +			       IRQF_SHARED, "xilinx-csi2rxss", xcsi2rxss);
> > +	if (ret) {
> > +		dev_err(core->dev, "Err = %d Interrupt handler reg
> failed!\n",
> > +			ret);
> > +		return ret;
> > +	}
> 
> When using this driver I have changed this to a threaded IRQ, moving most of
> the management out of interrupt context. The patch is super simple and it
> works fine, for my use case at least. Do you think a strict IRQ is really needed
> for some reason?
> 

Agree I should have moved this to a threaded IRQ. I will update it in next version.

> > +	xcsi2rxss_log_ipconfig(xcsi2rxss);
> > +
> > +	return 0;
> 
> This function references 'core->dev' a lot of times, so I'd rather add at the
> top of the function:
> 
>   struct device * const dev = &pdev->dev;
> 
> and then use simply 'dev' everywhere. This would keep lines shorter and
> more readable. It is also handy when copying/moving a line of code from
> one function to another if all of them have 'dev' called the same way so I
> tend to do use this pattern often.
> 

Agree with  you. It will be updated in next version.

> > +}
> > +
> > +static int xcsi2rxss_probe(struct platform_device *pdev) {
> > +	struct v4l2_subdev *subdev;
> > +	struct xcsi2rxss_state *xcsi2rxss;
> > +	struct xcsi2rxss_core *core;
> > +	struct resource *res;
> > +	int num_clks = ARRAY_SIZE(xcsi2rxss_clks);
> > +	int ret;
> > +
> > +	xcsi2rxss = devm_kzalloc(&pdev->dev, sizeof(*xcsi2rxss),
> GFP_KERNEL);
> > +	if (!xcsi2rxss)
> > +		return -ENOMEM;
> > +
> > +	core = &xcsi2rxss->core;
> > +	core->dev = &pdev->dev;
> 
> This function references 'dev' many times, sometimes as &pdev->dev, thers
> as 'core->dev', thus as above why not adding at the top of the
> function:
> 
>   struct device * const dev = &pdev->dev;
> 
> and simplify code using 'dev' always?
> 

True. I will do the change in next version.

> > +	core->clks = devm_kmemdup(core->dev, xcsi2rxss_clks,
> > +				  sizeof(xcsi2rxss_clks), GFP_KERNEL);
> > +	if (!core->clks)
> > +		return -ENOMEM;
> > +
> > +	/* Reset GPIO */
> > +	core->rst_gpio = devm_gpiod_get_optional(core->dev, "reset",
> > +						 GPIOD_OUT_HIGH);
> > +	if (IS_ERR(core->rst_gpio)) {
> > +		if (PTR_ERR(core->rst_gpio) != -EPROBE_DEFER)
> > +			dev_err(core->dev, "Video Reset GPIO not setup in
> DT");
> > +		return PTR_ERR(core->rst_gpio);
> > +	}
> > +
> > +	mutex_init(&xcsi2rxss->lock);
> 
> There are 3 'return' statements after this call, and mutex_destroy() won't be
> called if they trigger. Ok, probably no real effect as
> mutex_init() is just initializing data, but for the sake of well-written code you
> can simply move mutex_init()...
> 
> > +	ret = xcsi2rxss_parse_of(xcsi2rxss);
> > +	if (ret < 0)
> > +		return ret;
> > +
> > +	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> > +	core->iomem = devm_ioremap_resource(core->dev, res);
> > +	if (IS_ERR(core->iomem))
> > +		return PTR_ERR(core->iomem);
> > +
> > +	ret = clk_bulk_get(core->dev, num_clks, core->clks);
> > +	if (ret)
> > +		return ret;
> > +
> > +	ret = clk_bulk_prepare_enable(num_clks, core->clks);
> > +	if (ret)
> > +		goto err_clk_put;
> 
> ...here.
>

Good idea. This will be updated in next version.
 
> > +	if (core->rst_gpio) {
> > +		gpiod_set_value_cansleep(core->rst_gpio, 1);
> > +		/* minimum of 40 dphy_clk_200M cycles */
> > +		usleep_range(1, 2);
> > +		gpiod_set_value_cansleep(core->rst_gpio, 0);
> > +	}
> 
> 
> --
> Luca

Regards
Vishal Sagar