Re: [PATCH 1/2] usb: dwc2: optionally assert phy "full reset" when waking up

Thank you for reviewing, if you agree with my opinion, I would implement 
a new version as soon as  possible.


On 07/20/2016 09:36 AM, Rob Herring wrote:

On Tue, Jul 19, 2016 at 08:05:33PM +0800, Randy Li wrote:

quoted

From: Doug Anderson <redacted>

On the rk3288 USB host-only port (the one that's not the OTG-enabled
port) the PHY can get into a bad state when a wakeup is asserted (not
just a wakeup from full system suspend but also a wakeup from
autosuspend). The problem is caused by a design fault in IC, Rockchip
have confirmed it and fix this problem in the future IC model.

We can get the PHY out of its bad state by asserting its "port reset",
but unfortunately that seems to assert a reset onto the USB bus so it
could confuse things if we don't actually deenumerate / reenumerate the
device.

We can also get the PHY out of its bad state by fully resetting it using
the reset from the CRU (clock reset unit), which does a more full
reset.  The CRU-based reset appears to actually cause devices on the bus
to be removed and reinserted, which fixes the problem (albeit in a hacky
way).

It's unfortunate that we need to do a full re-enumeration of devices at
wakeup time, but this is better than alternative of letting the bus get
wedged.

Signed-off-by: Douglas Anderson <redacted>
Signed-off-by: Yunzhi Li <redacted>
Reviewed-by: Randy Li <redacted>
---
  Documentation/devicetree/bindings/usb/dwc2.txt |  7 +++++++
  drivers/usb/dwc2/core.h                        |  5 +++++
  drivers/usb/dwc2/core_intr.c                   | 14 ++++++++++++++
  drivers/usb/dwc2/platform.c                    | 13 +++++++++++++
  4 files changed, 39 insertions(+)

diff --git a/Documentation/devicetree/bindings/usb/dwc2.txt b/Documentation/devicetree/bindings/usb/dwc2.txt
index 20a68bf..40c63ae 100644
--- a/Documentation/devicetree/bindings/usb/dwc2.txt
+++ b/Documentation/devicetree/bindings/usb/dwc2.txt

@@ -20,6 +20,13 @@ Refer to clk/clock-bindings.txt for generic clock consumer properties
  Optional properties:
  - phys: phy provider specifier
  - phy-names: shall be "usb2-phy"
+- snps,need-phy-full-reset-on-wake: if present indicates that we need to reset

Bikeshedding, but 'snps,full-phy-reset-on-wake' is slightly shorter.

However, this isn't really even needed. It should be implied by the SoC
specific compatible string.

I would.

quoted

+  the PHY when we detect a wakeup due to a hardware errata.  If present you
+  must specify a "phy-full-reset" reset.
+
+Resets:
+- phy-full-reset (optional): Fully resets the PHY (Only used by rk3288 Soc).

This property belows in the phy node as that is where the reset is
attached to and why is it not using the standard binding "resets"?

Because the struct phy_ops doesn't have something like reset method. It 
is impossible to make a phy reset now. Also maybe it is not need to 
define a reset at dts, just implied do that reset that in code(as the 
way to reset is always same and only used by rk3288).

Rob

-- 
Randy Li
The third produce department


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