linux-kernel - Re: [PATCH 0/2] Disable SS instances in park mode for SC7180/ SC7280

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Message-ID: <e5f6e9bd-e19e-4997-a646-f3ddee84a5c8@linaro.org>
Date: Fri, 31 May 2024 16:26:00 +0200
From: Konrad Dybcio <konrad.dybcio@...aro.org>
To: Doug Anderson <dianders@...omium.org>
Cc: Krishna Kurapati <quic_kriskura@...cinc.com>,
 cros-qcom-dts-watchers@...omium.org, Krzysztof Kozlowski
 <krzk+dt@...nel.org>, Rob Herring <robh@...nel.org>,
 Bjorn Andersson <andersson@...nel.org>, Conor Dooley <conor+dt@...nel.org>,
 Stephen Boyd <swboyd@...omium.org>,
 Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
 Matthias Kaehlcke <mka@...omium.org>, linux-kernel@...r.kernel.org,
 linux-arm-msm@...r.kernel.org, devicetree@...r.kernel.org,
 quic_ppratap@...cinc.com, quic_jackp@...cinc.com
Subject: Re: [PATCH 0/2] Disable SS instances in park mode for SC7180/ SC7280

On 31.05.2024 4:17 PM, Doug Anderson wrote:
> Hi,
> 
> On Fri, May 31, 2024 at 5:33 AM Konrad Dybcio <konrad.dybcio@...aro.org> wrote:
>>
>> On 30.05.2024 3:34 PM, Doug Anderson wrote:
>>> Hi,
>>>
>>> On Thu, May 30, 2024 at 1:26 AM Krishna Kurapati
>>> <quic_kriskura@...cinc.com> wrote:
>>>>
>>>> When working in host mode, in certain conditions, when the USB
>>>> host controller is stressed, there is a HC died warning that comes up.
>>>> Fix this up by disabling SS instances in park mode for SC7280 and SC7180.
>>>>
>>>> Krishna Kurapati (2):
>>>>   arm64: dts: qcom: sc7180: Disable SS instances in park mode
>>>>   arm64: dts: qcom: sc7280: Disable SS instances in park mode
>>>>
>>>>  arch/arm64/boot/dts/qcom/sc7180.dtsi | 1 +
>>>>  arch/arm64/boot/dts/qcom/sc7280.dtsi | 1 +
>>>>  2 files changed, 2 insertions(+)
>>>
>>> FWIW, the test case I used to reproduce this:
>>>
>>> 1. Plug in a USB dock w/ Ethernet
>>> 2. Plug a USB 3 SD card reader into the dock.
>>> 3. Use lsusb -t to confirm both Ethernet and card reader are on USB3.
>>> 4. From a shell, run for i in $(seq 5); do dd if=/dev/sdb of=/dev/null
>>> bs=4M; done to read from the card reader.
>>> 5. At the same time, stress the Internet. If you've got a very fast
>>> Internet connection then running Google's "Internet speed test" did
>>> it, but I could also reproduce by just running this from a PC
>>> connected to the same network as my DUT: ssh ${DUT} "dd of=/dev/null"
>>> < /dev/zero
>>>
>>> I would also note that, though I personally reproduced this on sc7180
>>> and sc7280 boards and thus Krishna posted the patch for those boards,
>>> there's no reason to believe that this problem doesn't affect all of
>>> Qualcomm's SoCs. It would be nice if someone at Qualcomm could post a
>>> followup patch fixing this everywhere.
>>
>> Right, this sounds like a more widespread issue
>>
>> That said, I couldn't reproduce it on SC8280XP / X13s (which does NOT mean
>> 8280 isn't affected). My setup was:
>>
>> - USB3 5GB/s hub plugged into one of the side USBs
>>   - on-hub 1 Gb /s network hub connected straight to my router with a
>>     600 / 60 Mbps link, spamming speedtest-cli and dd-over-ssh
>>   - M.2 SSD connected over a USB adapter, nearing 280 MB/s speeds (the
>>     adapter isn't particularly speedy)
>>
>> So it stands to reason that it might not have been enough to trigger it.
> 
> In my case I wasn't using anything nearly as fast as a M.2 SSD. I was
> just using a normal USB3 SD card reader. That being said, multiple
> people at Qualcomm were able to replicate the issue without lots of
> back and forth, so I'd guess that the problem isn't that sensitive to
> the exact storage device. I will also note that it's not sensitive to
> the exact network device as I replicated it with two Ethernet adapters
> with very different chipsets.
> 
> My only guess is that somehow SC8280XP is faster and that changes the
> timing of how it handles interrupts. I guess you could try capping
> your cpufreq in sysfs and see if that makes a difference in
> reproducing. ;-) ...or maybe somehow SC8280XP has a newer version of
> the IP where they've fixed this?

Well, great minds think alike :P I did cap it to f_min on all cores, but
that didn't change the situation. Might have been worth to check out powering
off all cores except 0.. I might do that at one point.

My guess is that with a process node change, they might have used some
newer/better ip revision though. Remains to be seen.

Konrad

> 
> It would be interesting if someone with a SDM845 dragonboard could try
> replicating since that seems highly likely to reproduce, at least.
> 
> -Doug