On 07/13/2016 01:42 AM, Peter Chen wrote: > On Wed, Jul 13, 2016 at 09:27:31AM +0200, Philipp Zabel wrote: >> Am Mittwoch, den 13.07.2016, 10:06 +0800 schrieb Peter Chen: >>> Add binding doc for generic power sequence library. >>> >>> Signed-off-by: Peter Chen <peter.chen@xxxxxxx> >>> --- >>> .../bindings/power/pwrseq/pwrseq-generic.txt | 53 ++++++++++++++++++++++ >>> 1 file changed, 53 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..186c58c >>> --- /dev/null >>> +++ b/Documentation/devicetree/bindings/power/pwrseq/pwrseq-generic.txt >>> @@ -0,0 +1,53 @@ >>> +The generic power sequence library >>> + >>> +Some hard-wired USB/MMC devices need to do power sequence to let the >>> +device work normally, >> I would replace "to let the device work normally" with "before the >> device can be enumerated [on the bus]" here. >> > Ok. > >>> 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 >> As Joshua pointed out, is this even needed at all? >> > If no, how we decide whether allocates pwrseq instance through pwrseq > library or not? > The pwrseq driver is Linux specific. The dts is supposed to be OS agnostic. It seems to me that If a driver supports pwrseq and the dts elements are there, it should use them, e.g. if there is a clock, enable the clock. if there is a reset gpio then take the device into and out of reset during probe. Can you see a problem with that approach? -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
