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

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Date:   Fri, 8 Jul 2022 10:26:40 +0300
From:   Dmitry Osipenko <dmitry.osipenko@...labora.com>
To:     Viresh Kumar <viresh.kumar@...aro.org>
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 7/8/22 10:19, Viresh Kumar wrote:
> 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 ?

This patch is the cause.

>>  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.

I see that previously dev_pm_opp_set_config() had "_add_opp_table(dev,
false)", now it's "_add_opp_table(dev, true)".

Will take a closer look later on.

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

No problems :)

-- 
Best regards,
Dmitry