linux-kernel - Re: [PATCH 0/5] usb: dwc3: qcom: Allow runtime PM

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Date:   Mon, 27 Mar 2023 14:47:33 +0530
From:   Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
To:     Konrad Dybcio <konrad.dybcio@...aro.org>
Cc:     andersson@...nel.org, Thinh.Nguyen@...opsys.com,
        gregkh@...uxfoundation.org, mathias.nyman@...el.com,
        robh+dt@...nel.org, krzysztof.kozlowski+dt@...aro.org,
        linux-arm-msm@...r.kernel.org, linux-usb@...r.kernel.org,
        linux-kernel@...r.kernel.org, devicetree@...r.kernel.org
Subject: Re: [PATCH 0/5] usb: dwc3: qcom: Allow runtime PM

On Mon, Mar 27, 2023 at 11:01:35AM +0200, Konrad Dybcio wrote:
> 
> 
> On 25.03.2023 17:52, Manivannan Sadhasivam wrote:
> > Hi,
> > 
> > This series allows the dwc3-qcom driver to do runtime PM itself without
> > userspace intervention. Still, userspace is required to enable runtime PM
> > for dwc3 glue and xhci drivers as we cannot enable runtime PM for them.
> > But this series avoids one more additional step.
> What sort of 'userspace intervention' are we talking about?
> echo mem > /sys/power/state?
> 

I forgot to add that bit:

echo auto > /sys/devices/platform/soc@...8f8800.usb/a800000.usb/xhci-hcd.1.auto/power/control
echo auto > /sys/devices/platform/soc@...8f8800.usb/a800000.usb/power/control

You need to set "auto" for the runtime control for both xhci and dwc drivers.

Then if you don't connect a usb device, all 3 drivers (dwc3-qcom, dwc3, and
xhci) will become runtime suspended after a delay of 5s (default delay).

This can be confirmed by:

cat /sys/devices/platform/soc@...8f8800.usb/power/runtime_status

After connecting a usb device, they will all become "active".

Thanks,
Mani

> Konrad
> > 
> > While enabling runtime PM, I noticed that the xhci driver suspends before
> > catching the xhci interrupts during resume. This ended up deferring the
> > device enumeration for some time. So I included a patch adding autosuspend
> > delay of 200ms to the xhci driver. With this delay, usb enumeration happens
> > properly.
> > 
> > This series has been tested on SC8280XP-CRD and RB5 devices.
> > 
> > Thanks,
> > Mani
> > 
> > Manivannan Sadhasivam (5):
> >   arm64: dts: qcom: sc8280xp: Add missing dwc3 quirks
> >   xhci: host: Use 200ms autosuspend delay for runtime suspend
> >   usb: dwc3: qcom: Fix null ptr access during runtime_suspend()
> >   usb: dwc3: qcom: Clear pending interrupt before enabling wake
> >     interrupt
> >   usb: dwc3: qcom: Allow runtime PM
> > 
> >  arch/arm64/boot/dts/qcom/sc8280xp.dtsi | 14 ++++++++++++++
> >  drivers/usb/dwc3/dwc3-qcom.c           | 13 +++++++++----
> >  drivers/usb/host/xhci-plat.c           |  2 ++
> >  3 files changed, 25 insertions(+), 4 deletions(-)
> > 

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