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

On Thu, Jul 07, 2016 at 04:53:07PM -0700, Joshua Clayton wrote:

On 07/07/2016 02:47 AM, Philipp Zabel wrote:

quoted

Am Donnerstag, den 07.07.2016, 17:14 +0800 schrieb Peter Chen:

quoted

Add binding doc for generic power sequence library.

Signed-off-by: Peter Chen <redacted>
---
 .../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.

quoted

+- 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?

The power sequence does not include reset process only, it may include clock
and power as well.

-- 

Best Regards,
Peter Chen