Subject: [PATCH 1/6] binding-doc: power: pwrseq-generic: add binding doc for generic power sequence library

From: [email-masked] (Joshua Clayton)
Date: Thu, 7 Jul 2016 16:53:07 -0700

On 07/07/2016 02:47 AM, Philipp Zabel wrote:
> Am Donnerstag, den 07.07.2016, 17:14 +0800 schrieb Peter Chen:
>> Add binding doc for generic power sequence library.
>>
>> Signed-off-by: Peter Chen <[email-masked]>
>> ---
>>  .../bindings/power/pwrseq/pwrseq-generic.txt       | 56 ++++++++++++++++++++++
>>  1 file changed, 56 insertions(+)
>>  create mode 100644 Documentation/devicetree/bindings/power/pwrseq/pwrseq-generic.txt
>>
>> diff --git a/Documentation/devicetree/bindings/power/pwrseq/pwrseq-generic.txt b/Documentation/devicetree/bindings/power/pwrseq/pwrseq-generic.txt
>> new file mode 100644
>> index 0000000..4b23834
>> --- /dev/null
>> +++ b/Documentation/devicetree/bindings/power/pwrseq/pwrseq-generic.txt
>> @@ -0,0 +1,56 @@
>> +The generic power sequence library
>> +
>> +Some hard-wired USB/MMC devices need to do power sequence to let the
>> +device work normally, the typical power sequence like: enable USB
>> +PHY clock, toggle reset pin, etc. But current Linux USB driver
>> +lacks of such code to do it, it may cause some hard-wired USB devices
>> +works abnormal or can't be recognized by controller at all. The
>> +power sequence will be done before this device can be found at USB
>> +bus.
>> +
>> +The power sequence properties is under the device node.
>> +
>> +Required properties:
>> +- power-sequence: this device needs to do power sequence before enumeration
>> +
>> +Optional properties:
>> +- clocks: the input clock for device.
>> +- clock-name: must be "pwrseq-clk"
> The "-clk" in the clock name is redundant.
>
>> +- pwrseq-reset-gpios: Should specify the GPIO for reset.
>> +- pwrseq-reset-duration-us: the duration in microsecond for assert reset signal.
> I understand you want to make it explicit that this GPIO is for the
> pwrseq library, but are we really gaining anything over just calling
> these reset-gpios and reset-duration-us?
> The same applies to the clock name above.
using  reset-gpios makes sense to  me too.
The above "power-sequence" might then be better called "reset-on-init",
But really, if a device has a reset gpio shouldn't the default behavior be to
reset it on boot and when coming back from sleep?
Is a special property even needed?
>
>> +Below is the example of USB power sequence properties on USB device
>> +nodes which have two level USB hubs.
>> +
>> +&usbotg1 {
>> +	vbus-supply = <&reg_usb_otg1_vbus>;
>> +	pinctrl-names = "default";
>> +	pinctrl-0 = <&pinctrl_usb_otg1_id>;
>> +	status = "okay";
>> +
>> +	#address-cells = <1>;
>> +	#size-cells = <0>;
>> +	hub: genesys at 1 {
>> +		compatible = "usb5e3,608";
>> +		reg = <1>;
>> +
>> +		power-sequence;
>> +		clocks = <&clks IMX6SX_CLK_CKO>;
>> +		clock-names = "pwrseq-clk";
>> +		pwrseq-reset-gpios = <&gpio4 5 GPIO_ACTIVE_LOW>; /* hub reset pin */
>> +		pwrseq-reset-duration-us = <10>;
>> +
>> +		#address-cells = <1>;
>> +		#size-cells = <0>;
>> +		ethernet: asix at 1 {
>> +			compatible = "usbb95,1708";
>> +			reg = <1>;
>> +
>> +			power-sequence;
>> +			clocks = <&clks IMX6SX_CLK_IPG>;
>> +			clock-names = "pwrseq-clk";
>> +			pwrseq-reset-gpios = <&gpio4 6 GPIO_ACTIVE_LOW>; /* ethernet_rst */
>> +			pwrseq-reset-duration-us = <15>;
>> +		};
> This looks weird. The hub and ethernet chips don't have "pwrseq" clock
> and reset input pins. I'd remove the clock-names and pwrseq- reset
> prefix.
>
> regards
> Philipp
>
>
> _______________________________________________
> linux-arm-kernel mailing list
> linux-arm-kernel at lists.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel