From: Evan Green <evgreen@chromium.org>
To: Akash Asthana <akashast@codeaurora.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Andy Gross <agross@kernel.org>,
Bjorn Andersson <bjorn.andersson@linaro.org>,
wsa@the-dreams.de, Mark Brown <broonie@kernel.org>,
Mark Rutland <mark.rutland@arm.com>,
Rob Herring <robh+dt@kernel.org>,
linux-i2c@vger.kernel.org, linux-spi@vger.kernel.org,
"open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS"
<devicetree@vger.kernel.org>, Stephen Boyd <swboyd@chromium.org>,
Manu Gautam <mgautam@codeaurora.org>,
linux-arm-msm <linux-arm-msm@vger.kernel.org>,
linux-serial@vger.kernel.org,
Doug Anderson <dianders@chromium.org>
Subject: Re: [PATCH V2 3/8] soc: qcom-geni-se: Add interconnect support to fix earlycon crash
Date: Fri, 20 Mar 2020 09:30:23 -0700 [thread overview]
Message-ID: <CAE=gft6AGkcdUAkoyevZgmtBgaiEkoQzzJcg7sYjbpy5Kh2fyA@mail.gmail.com> (raw)
In-Reply-To: <a7227a1f-00a1-0818-80f3-904fe264f864@codeaurora.org>
On Fri, Mar 20, 2020 at 3:22 AM Akash Asthana <akashast@codeaurora.org> wrote:
>
> Hi Evan, Matthias,
>
> On 3/20/2020 1:13 AM, Matthias Kaehlcke wrote:
> > On Wed, Mar 18, 2020 at 02:24:35PM +0530, Akash Asthana wrote:
> >> Hi Matthias,
> >>
> >> On 3/17/2020 11:59 PM, Matthias Kaehlcke wrote:
> >>> Hi Akash,
> >>>
> >>> On Tue, Mar 17, 2020 at 04:27:47PM +0530, Akash Asthana wrote:
> >>>> Hi Matthias,
> >>>>
> >>>> On 3/14/2020 2:14 AM, Matthias Kaehlcke wrote:
> >>>>> Hi Akash,
> >>>>>
> >>>>> On Fri, Mar 13, 2020 at 06:42:09PM +0530, Akash Asthana wrote:
> >>>>>> V1 patch@https://patchwork.kernel.org/patch/11386469/ caused SC7180 system
> >>>>>> to reset at boot time.
> >>>>> The v1 patch isn't relevant in the commit message, please just describe the
> >>>>> problem. Also the crash only occurs when earlycon is used.
> >>>> ok
> >>>>>> As QUP core clock is shared among all the SE drivers present on particular
> >>>>>> QUP wrapper, the reset seen is due to earlycon usage after QUP core clock
> >>>>>> is put to 0 from other SE drivers before real console comes up.
> >>>>>>
> >>>>>> As earlycon can't vote for it's QUP core need, to fix this add ICC
> >>>>>> support to common/QUP wrapper driver and put vote for QUP core from
> >>>>>> probe on behalf of earlycon and remove vote during sys suspend.
> >>>>> Only removing the vote on suspend isn't ideal, the system might never get
> >>>>> suspended. That said I don't have a really good alternative suggestion.
> >>>>>
> >>>>> One thing you could possibly do is to launch a delayed work, check
> >>>>> console_device() every second or so and remove the vote when it returns
> >>>>> non-NULL. Not claiming this would be a great solution ...
> >>>>>
> >>>>> The cleanest solution might be a notifier when the early console is
> >>>>> unregistered, it seems somewhat over-engineered though ... Then again
> >>>>> other (future) uart drivers with interconnect support might run into
> >>>>> the same problem.
> >>>> We are hitting this problem because QUP core clocks are shared among all the
> >>>> SE driver present in particular QUP wrapper, if other HW controllers has
> >>>> similar architecture we will hit this issue.
> >>>>
> >>>> How about if we expose an API from common driver(geni-se) for putting QUP
> >>>> core BW vote to 0.
> >>>>
> >>>> We call this from console probe just after uart_add_one_port call (console
> >>>> resources are enabled as part of this call) to put core quota to 0 on behalf
> >>>> of earlyconsole?
> >>> From my notes from earlier debugging I have doubts this would work:
> >>>
> >>> There is a short window where the early console and the 'real' console coexist:
> >>>
> >>> [ 3.858122] printk: console [ttyMSM0] enabled
> >>> [ 3.875692] printk: bootconsole [qcom_geni0] disabled
> >>>
> >>> The reset probably occurs when the early console tries to write, but the ICC
> >>> is effectively disabled because ttyMSM0 and the other geni ports are runtime
> >>> suspended.
> >> Code flow from console driver probe(qcom_geni_serial.c)
> >>
> >> uart_add_one_port--->uart_configure_port--->{ 1) uart_change_pm(enable
> >> console resources) 2)register_console(boot to real console switch happens
> >> here)}
> >>
> >> Console resources are not disabled from anywhere before the switch happens
> >> completely. I meant to say until we saw below logs.
> >>
> >> [ 3.875692] printk: bootconsole [qcom_geni0] disabled
> >>
> >> I think the board reset issue cannot occur during the window where early
> >> console and 'real' console coexist.
> > Thanks for the clarification! Indeed my notes were only a hypothesis, I
> > don't see evidence that there is an actual downvote shortly after console
> > registration.
> >
> >> I have validated proposed solution by me, it is working fine.
> >>
> >> Currently voting is done for every QUP and not only to which earlycon is
> >> connect, with the above approach we can't remove vote from other QUPs.
> >>
> >> However we can limit voting only to earlycon QUP by removing interconnect
> >> from DT node of other QUPs.
> >>
> >> I am not sure how clean is this solution.
> > I'm more inclined towards a solution along the lines of what Evan
> > proposed, i.e. delaying the votes (either in geni or ICC) until we
> > are ready.
>
> Based on discussion I think the delayed solution is most suited if
> implemented in ICC core because other ICC client might face the similar
> problem.
>
> However for geni case I am more inclined towards below proposed solution.
>
> -----------------------------------------------------------------------------------------------------
>
> How about if we expose an API from common driver(geni-se) for putting QUP
> core BW vote to 0.
>
> We call this from console probe just after uart_add_one_port call (console
> resources are enabled as part of this call) to put core quota to 0 on behalf
> of earlyconsole?
This seems ok to me. Earlycon sets up a vote, and then real probe
tears it down. As long as in the shuffle of all of these things into
SE library helpers you still have a way of differentiating the
earlycon vote from the real vote. In other words, don't reuse this
early icc_path for the real UART vote. You should probably also
destroy the path once you've voted zero on it.
-Evan
next prev parent reply other threads:[~2020-03-20 16:31 UTC|newest]
Thread overview: 50+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-03-13 13:12 [PATCH V2 0/8] Add interconnect support to QSPI and QUP drivers Akash Asthana
2020-03-13 13:12 ` [PATCH V2 1/8] interconnect: Add devm_of_icc_get() as exported API for users Akash Asthana
2020-03-13 16:26 ` Matthias Kaehlcke
2020-03-27 23:02 ` Bjorn Andersson
2020-03-13 13:12 ` [PATCH V2 2/8] soc: qcom: geni: Support for ICC voting Akash Asthana
2020-03-13 16:42 ` Matthias Kaehlcke
2020-03-17 9:58 ` Akash Asthana
2020-03-17 19:06 ` Evan Green
[not found] ` <74851dda-296d-cdc5-2449-b9ec59bbc057@codeaurora.org>
2020-03-20 16:45 ` Evan Green
2020-03-27 5:33 ` Akash Asthana
2020-03-13 13:12 ` [PATCH V2 3/8] soc: qcom-geni-se: Add interconnect support to fix earlycon crash Akash Asthana
2020-03-13 20:44 ` Matthias Kaehlcke
2020-03-17 10:57 ` Akash Asthana
2020-03-17 18:29 ` Matthias Kaehlcke
2020-03-18 8:54 ` Akash Asthana
2020-03-19 19:43 ` Matthias Kaehlcke
2020-03-20 10:22 ` Akash Asthana
2020-03-20 16:30 ` Evan Green [this message]
2020-03-27 5:04 ` Akash Asthana
2020-03-27 23:23 ` Bjorn Andersson
2020-03-31 10:55 ` Akash Asthana
2020-03-17 19:08 ` Evan Green
2020-03-17 19:46 ` Doug Anderson
2020-03-18 10:57 ` Akash Asthana
2020-03-18 16:22 ` Evan Green
2020-03-13 13:12 ` [PATCH V2 4/8] tty: serial: qcom_geni_serial: Add interconnect support Akash Asthana
2020-03-13 21:28 ` Matthias Kaehlcke
2020-03-17 11:48 ` Akash Asthana
2020-03-17 19:08 ` Matthias Kaehlcke
2020-03-18 12:23 ` Akash Asthana
2020-03-19 20:42 ` Matthias Kaehlcke
2020-03-20 10:35 ` Akash Asthana
2020-03-13 13:12 ` [PATCH V2 5/8] i2c: i2c-qcom-geni: " Akash Asthana
2020-03-14 0:17 ` Matthias Kaehlcke
2020-03-17 11:51 ` Akash Asthana
2020-03-13 13:12 ` [PATCH V2 6/8] spi: spi-geni-qcom: " Akash Asthana
2020-03-13 13:16 ` Mark Brown
2020-03-17 9:35 ` Akash Asthana
2020-03-17 13:06 ` Mark Brown
2020-03-20 13:52 ` Akash Asthana
2020-03-14 0:41 ` Matthias Kaehlcke
2020-03-17 12:11 ` Akash Asthana
2020-03-13 13:12 ` [PATCH V2 7/8] spi: spi-qcom-qspi: " Akash Asthana
2020-03-14 0:58 ` Matthias Kaehlcke
2020-03-17 12:13 ` Akash Asthana
2020-03-17 19:08 ` Evan Green
2020-03-18 13:48 ` Akash Asthana
2020-03-18 16:30 ` Evan Green
2020-03-20 5:35 ` Akash Asthana
2020-03-13 13:12 ` [PATCH V2 8/8] arm64: dts: sc7180: Add interconnect for QUP and QSPI Akash Asthana
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