Re: [PATCH 0/4] Patches to fix remote wakeup on rk3288 dwc2 "host" port

[Rob Herring]

On Sat, Oct 24, 2015 at 4:22 PM, Doug Anderson <dianders@xxxxxxxxxxxx> wrote:
> Rob,
>
> On Sat, Oct 24, 2015 at 11:10 AM, Rob Herring <robh@xxxxxxxxxx> wrote:
>> On 10/23/2015 01:28 PM, Douglas Anderson wrote:
>>> The "host1" port (AKA the dwc2 port that isn't the OTG port) on rk3288
>>> has a hardware errata that causes everything to get confused when we get
>>> a remote wakeup.  It appears that the "port reset" bit that's in the USB
>>> phy (located in the rk3288 GRF) fixes things up and appears safe to do.
>>>
>>> This series of patches exports the "port reset" from the PHY and then
>>> hooks it up to dwc2 through a quirk.
>>>
>>> I've tested this series atop a bit of a conglomeration of Heiko's github
>>> "somewhat stable" branch (v4.3-rc3-876-g6509232) but with Greg KH's
>>> usb-next merged in.
>>>
>>> These patches currently conflict with patches that I posted previously
>>> to enable USB wakeup from S3, specifically:
>>> * https://patchwork.kernel.org/patch/6727081/
>>> * https://patchwork.kernel.org/patch/6727121/
>>> ...those patches no longer apply anyway, so presumably they need to be
>>> reposted and I can do so later atop these patches.
>>>
>>>
>>> Douglas Anderson (4):
>>>   phy: rockchip-usb: Support the PHY's "port reset"
>>>   usb: dwc2: optionally assert phy "port reset" when waking up
>>>   ARM: dts: rockchip: Enable the USB phys as reset providers on rk3288
>>>   ARM: dts: rockchip: Point rk3288 dwc2 usb at phy port reset
>>>
>>>  .../devicetree/bindings/phy/rockchip-usb-phy.txt   |  6 ++
>>>  Documentation/devicetree/bindings/usb/dwc2.txt     |  7 ++
>>>  arch/arm/boot/dts/rk3288.dtsi                      |  8 +++
>>>  drivers/phy/phy-rockchip-usb.c                     | 74 ++++++++++++++++++++++
>>>  drivers/usb/dwc2/core.h                            |  5 ++
>>>  drivers/usb/dwc2/core_intr.c                       |  7 ++
>>>  drivers/usb/dwc2/platform.c                        | 13 ++++
>>>  7 files changed, 120 insertions(+)
>>
>> A DT reset controller seems like a bit of an overkill here. I think this
>> would be much more simple if we just add a phy reset hook to the phy
>> subsystem.
>
> Adding a reset hook in the PHY subsystem does seem like a reasonable
> idea to me.  I was considering it in an earlier version of this series
> that actually used a reset of the PHY to the fix the stuck dwc2.
>
> ...but I think that even if the phy subsystem had a reset hook it
> wouldn't be the ideal solution here.  When we assert the PHY "port
> reset" we're not actually fully resetting the PHY.  We're instead
> doing some sort of a more minor "state machine" reset in the PHY.
> This appears better (in my case) than resetting the whole PHY because
> it doesn't force a de-enumeration / re-enumeration.  Exposing this
> more minor reset as a PHY reset seems wrong to me.  ...and it also
> precludes us later also exposing the more full reset through the PHY
> framework if that later becomes useful.

Doesn't creating a binding also have similar possibility? Maybe an
"attach host" or re-init hook would be more appropriate. I'm sure
there are other such cases where the host and phy need more tight
coupling. I recently had a similar case where there was an interleaved
sequence of phy and host register writes. I managed rework things and
avoid changing the phy interface, but there will certainly be cases
where we can't.

Changing function names in the kernel is easy. Changing the binding
later not so much. Also as we're looking toward dependency handling,
this creates a circular dependency. We'll probably have to deal with
those anyway, but here it seems a bit pointless. We already have a
connection between the host and phy defined. Let's use that and not
define another.

> ...we could, of course, re-invent the reset framework (with string or
> integral IDs so we can assert different types of resets) within the
> PHY framework.  That doesn't seem ideal to me, but if that's what
> others want to do then I guess it would be OK...

I think that should already be possible as you can have multiple
cells. Of course, you have to plan for that with your cell values.

Rob
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