Re: Device Tree Child Node Parsing Question

[He YunLei <heyunlei-hv44wF8Li93QT0dZR+AlfA@public.gmane.org>]

On 2014/12/24 0:34, Thor Thayer wrote:
> Hi,
>
> What is the best way to queue devicetree child nodes so the node is passed in the platform_device pointer to the probe() function?
>
> Documentation/devicetree/usage-model.txt has the following:
>
> "For Linux DT support, the generic behaviour is for child devices to be registered by the parent's device driver at driver .probe() time."
>
> "Actually, it turns out that registering children of some platform_devices as more platform_devices is a common pattern, and the
> device tree support code reflects that and makes the above example
> simpler.  The second argument to of_platform_populate() is an
> of_device_id table, and any node that matches an entry in that table
> will also get its child nodes registered."
>
>
> I tried calling of_platform_populate() in the probe of the a10_sysctl node but it doesn't appear to setup the platform device data properly for the sub-child nodes.
>
> The top child node (a10_sysctl) is probed properly and has a valid of_node passed in. However, the sub-child nodes such as gpio4 have null passed in for pdev->dev.of_node (gpio4 probe prototype is int a10sycon_gpio_probe(struct platform_device *pdev).

Gpio4 is the child node of a10_sysctl?  You call of_platform_populate() in the probe of the a10_sysctl node,
this action does no matter with gpio4.

Yours,
Yunlei
>
> My current solution is to call of_find_matching_node() in a10sycon_gpio_probe() to get a valid node pointer but other examples tend to dereference pdev->dev.of_node.
>
> Thank you in advance for your insight.
>
> Thor
>
>
> My device tree looks like this:
>
> / {
>      soc {
>          spi0: spi@fff00000 {
>           compatible = "snps,dw-spi-mmio";
>           #address-cells = <1>;
>           #size-cells = <0>;
>           reg = <0xfff00000 0x1000>;
>           interrupts = <0 154 4>;
>           num-chipselect = <4>;
>           clocks = <&per_base_clk>;
>           status = "okay";
>
>               a10_sysctl: a10_sysctl@0 {
>          compatible = "altr,a10sycon";
>          reg = <0>;
>          interrupt-parent = <&gpio2>;
>          /* low-level active IRQ at GPIO2_24 */
>          interrupts = <24 0x8>;
>          interrupt-controller;
>          #interrupt-cells = <2>;
>          spi-max-frequency = <100000>;
>
>          gpio4: gpio-controller {
>              compatible = "altr,a10sycon-gpio";
>              gpio-controller;
>              #gpio-cells = <2>;
>              ngpios = <16>;
>          };
>
>          a10rst: a10rst {
>              compatible = "altr,a10sycon-reset";
>              #reset-cells = <1>;
>          };
>          };
>      };
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