linux-kernel - Re: [PATCH V2 00/13] OPP: Add support for multiple clocks*

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Date:   Fri, 8 Jul 2022 12:49:26 +0530
From:   Viresh Kumar <viresh.kumar@...aro.org>
To:     Dmitry Osipenko <dmitry.osipenko@...labora.com>
Cc:     Chanwoo Choi <cw00.choi@...sung.com>,
        Dmitry Osipenko <digetx@...il.com>,
        Jonathan Hunter <jonathanh@...dia.com>,
        Kyungmin Park <kyungmin.park@...sung.com>,
        MyungJoo Ham <myungjoo.ham@...sung.com>,
        Nishanth Menon <nm@...com>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Stephen Boyd <sboyd@...nel.org>,
        Thierry Reding <thierry.reding@...il.com>,
        Viresh Kumar <vireshk@...nel.org>, linux-pm@...r.kernel.org,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-tegra@...r.kernel.org,
        Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>,
        Rob Herring <robh@...nel.org>
Subject: Re: [PATCH V2 00/13] OPP: Add support for multiple clocks*

On 07-07-22, 22:43, Dmitry Osipenko wrote:
> This patch breaks Tegra again, please take a look:

Damn, not again :(

>    OPP: Remove dev{m}_pm_opp_of_add_table_noclk()

Why did you mention this patch ? This just removed an unused API,
Tegra should have broke because of something else, isn't it ?

>  8<--- cut here ---
>  Unable to handle kernel paging request at virtual address ffffffff
>  [ffffffff] *pgd=9effd861, *pte=00000000, *ppte=00000000
>  Internal error: Oops: 37 [#1] PREEMPT SMP ARM
>  Modules linked in:
>  CPU: 3 PID: 8 Comm: kworker/u8:0 Not tainted
> 5.19.0-rc1-00040-g30b62d123f4f #82
>  Hardware name: NVIDIA Tegra SoC (Flattened Device Tree)
>  Workqueue: events_unbound deferred_probe_work_func
>  PC is at _opp_compare_key+0x40/0xc4
>  LR is at 0xfffffffb

How is LR set to such an address ?

>  pc : [<c0b91b54>]    lr : [<fffffffb>]    psr: 20000113
>  sp : df831b08  ip : c33cd4d0  fp : df831b24
>  r10: c2586078  r9 : c258606c  r8 : 00000000
>  r7 : 00000000  r6 : 00000001  r5 : c33cd480  r4 : c2586000
>  r3 : 00000000  r2 : c33cd480  r1 : c258606c  r0 : c2586000
>  Flags: nzCv  IRQs on  FIQs on  Mode SVC_32  ISA ARM  Segment none
>  Control: 10c5387d  Table: 8000404a  DAC: 00000051
> ...
>  Backtrace:
>   _opp_compare_key from _set_opp+0x80/0x408

Whatever happened, happened from _opp_compare_key() and I tried to
look at it many times, couldn't figure out what's wrong there.

For the device in question, pmc I think, we don't have any "opp-hz"
property in the DT, but still the OPP core will fetch its clock and
set clk_count to 1. But this was working earlier too, we were
comparing the rate anyways. I think one of _opp_compare_rate() or
_opp_compare_bw() is broken here, but I just couldn't figure out. The
rate one should run one loop and bw one should just return. I don't
see why a crash should come out eventually.

Can you help debug this a bit ? Also see what are the values of
opp_table->path_count and opp_table->clk_count, should be 0 and 1
AFAICT.

Sorry about this Dmitry, I think we are all settled and again went
into crap.

-- 
viresh