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SubjectRE: [PATCH 0/3] Dynamic CPU frequency switching for the HiFive
Date
Hi Andreas,

> -----Original Message-----
> From: Andreas Schwab <schwab@suse.de>
> Sent: 01 July 2020 16:11
> To: Yash Shah <yash.shah@sifive.com>
> Cc: Paul Walmsley ( Sifive) <paul.walmsley@sifive.com>;
> palmer@dabbelt.com; robh+dt@kernel.org; linux-riscv@lists.infradead.org;
> linux-kernel@vger.kernel.org; devicetree@vger.kernel.org; Sachin Ghadi
> <sachin.ghadi@sifive.com>; aou@eecs.berkeley.edu; anup@brainfault.org;
> lollivier@baylibre.com; Green Wan <green.wan@sifive.com>;
> atish.patra@wdc.com; alistair.francis@wdc.com; deepa.kernel@gmail.com;
> bmeng.cn@gmail.com
> Subject: Re: [PATCH 0/3] Dynamic CPU frequency switching for the HiFive
>
> [External Email] Do not click links or attachments unless you recognize the
> sender and know the content is safe
>
> On Jun 16 2020, Yash Shah wrote:
>
> > The patch series adds the support for dynamic CPU frequency switching
> > for FU540-C000 SoC on the HiFive Unleashed board. All the patches are
> > based on Paul Walmsley's work.
> >
> > This series is based on Linux v5.7 and tested on HiFive unleashed board.
>
> I'm using that patch with 5.7.5.
>
> It appears to interfer with serial output when using the ondemand governor.
>
> I also see soft lockups when using the performance governor:
>
> [ 101.587527] rcu: INFO: rcu_sched self-detected stall on CPU
> [ 101.592322] rcu: 0-...!: (932 ticks this GP)
> idle=11a/1/0x4000000000000004 softirq=4301/4301 fqs=4
> [ 101.601432] (t=6001 jiffies g=4017 q=859) [ 101.605514] rcu: rcu_sched
> kthread starved for 5984 jiffies! g4017 f0x0 RCU_GP_WAIT_FQS(5) -
> >state=0x0 ->cpu=2 [ 101.615494] rcu: RCU grace-period kthread stack
> dump:
> [ 101.620530] rcu_sched R running task 0 10 2 0x00000000
> [ 101.627560] Call Trace:
> [ 101.630004] [<ffffffe00085a7e2>] __schedule+0x25c/0x616 [ 101.635205]
> [<ffffffe00085abde>] schedule+0x42/0xb2 [ 101.640070]
> [<ffffffe00085d0ba>] schedule_timeout+0x56/0xb8 [ 101.645626]
> [<ffffffe000263c34>] rcu_gp_fqs_loop+0x208/0x248 [ 101.651266]
> [<ffffffe0002666de>] rcu_gp_kthread+0xc2/0xcc [ 101.656651]
> [<ffffffe00022654e>] kthread+0xda/0xec [ 101.661426] [<ffffffe00020140a>]
> ret_from_exception+0x0/0xc [ 101.666977] Task dump for CPU 0:
> [ 101.670187] loop0 R running task 0 655 2 0x00000008
> [ 101.677218] Call Trace:
> [ 101.679657] [<ffffffe0002028ae>] walk_stackframe+0x0/0xaa [
> 101.685036] [<ffffffe000202b76>] show_stack+0x2a/0x34 [ 101.690074]
> [<ffffffe0002319b0>] sched_show_task.part.0+0xc2/0xd2 [ 101.696154]
> [<ffffffe00022bb9c>] sched_show_task+0x64/0x66 [ 101.701618]
> [<ffffffe000231afe>] dump_cpu_task+0x3e/0x48 [ 101.706916]
> [<ffffffe000267762>] rcu_dump_cpu_stacks+0x94/0xce [ 101.712731]
> [<ffffffe0002631f6>] print_cpu_stall+0x116/0x18a [ 101.718375]
> [<ffffffe000264a46>] check_cpu_stall+0xcc/0x1a2 [ 101.723929]
> [<ffffffe000264b52>] rcu_pending.constprop.0+0x36/0xaa [ 101.730094]
> [<ffffffe000266ab2>] rcu_sched_clock_irq+0xa6/0xea [ 101.735913]
> [<ffffffe00026d1be>] update_process_times+0x1e/0x42 [ 101.741821]
> [<ffffffe0002793bc>] tick_sched_handle+0x26/0x52 [ 101.747456]
> [<ffffffe0002798fe>] tick_sched_timer+0x6a/0xd0 [ 101.753015]
> [<ffffffe00026d9be>] __run_hrtimer.constprop.0+0x50/0xe8
> [ 101.759353] [<ffffffe00026da9e>] __hrtimer_run_queues+0x48/0x6c [
> 101.765254] [<ffffffe00026e410>] hrtimer_interrupt+0xca/0x1d4 [
> 101.770985] [<ffffffe0006ceef8>] riscv_timer_interrupt+0x32/0x3a [
> 101.776976] [<ffffffe00085e17c>] do_IRQ+0xa4/0xb8 [ 101.781663]
> [<ffffffe00020140a>] ret_from_exception+0x0/0xc
>
> Andreas.
>
> --
> Andreas Schwab, SUSE Labs, schwab@suse.de GPG Key fingerprint = 0196
> BAD8 1CE9 1970 F4BE 1748 E4D4 88E3 0EEA B9D7 "And now for something
> completely different."

I am looking into the issues you reported. I will update soon.
Thanks for testing.

- Yash

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