Device Tree Child Node Parsing Question

Device Tree Child Node Parsing Question

[Thor Thayer]

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).

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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Re: Device Tree Child Node Parsing Question

[Rob Herring]

On Tue, Dec 23, 2014 at 10:34 AM, Thor Thayer
<tthayer-yzvPICuk2ABMcg4IHK0kFoH6Mc4MB0Vx@public.gmane.org> 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).
>
> 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.

This should work. There are quite a few users already including unit
tests. Can you tell what you are doing differently from those users?

Rob

>
> 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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Re: Device Tree Child Node Parsing Question

[He YunLei]

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>;
>          };
>          };
>      };
> --
> To unsubscribe from this list: send the line "unsubscribe devicetree" in
> the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
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>
>

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Re: Device Tree Child Node Parsing Question

[Thor Thayer]

On 12/26/2014 01:40 PM, Rob Herring wrote:
> On Tue, Dec 23, 2014 at 10:34 AM, Thor Thayer
> <tthayer-yzvPICuk2ABMcg4IHK0kFoH6Mc4MB0Vx@public.gmane.org> 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.
>>

<snip>
>
> This should work. There are quite a few users already including unit
> tests. Can you tell what you are doing differently from those users?
>
> Rob
>
>>

<snip>

Just to tie up this conversation in case anyone else has an issue, it 
ended up being my debug issue. The of_platform_populate() was working 
properly. The issue was that I was also calling a mfd_add_devices() 
using a devices table and I was watching the mfd_add_devices() probe. 
Simply removing the mfd_add_devices() and the table and using 
of_platform_populate() as below worked.

of_platform_populate(spi->dev.of_node, a10sycon_spi_of_match,
		     NULL, &spi->dev);

Thanks!
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