Re: [PATCH] clocksource: Add driver for the Ingenic JZ47xx OST

[Daniel Lezcano <daniel.lezcano@linaro.org>]

On 07/11/2019 16:56, Paul Cercueil wrote:
> Hi Daniel,
> 
> On 2019-08-16 16:54, Daniel Lezcano wrote:
>> On 09/08/2019 14:38, Paul Cercueil wrote:
>>> From: Maarten ter Huurne <maarten@treewalker.org>
>>>
>>> OST is the OS Timer, a 64-bit timer/counter with buffered reading.
>>>
>>> SoCs before the JZ4770 had (if any) a 32-bit OST; the JZ4770 and
>>> JZ4780 have a 64-bit OST.
>>>
>>> This driver will register both a clocksource and a sched_clock to the
>>> system.
>>>
>>> Signed-off-by: Maarten ter Huurne <maarten@treewalker.org>
>>> Signed-off-by: Paul Cercueil <paul@crapouillou.net>
>>> Tested-by: Mathieu Malaterre <malat@debian.org>
>>> Tested-by: Artur Rojek <contact@artur-rojek.eu>
>>> ---
>>>
>>
>> [ ... ]
>>
>>> +    err = clocksource_register_hz(cs, rate);
>>> +    if (err) {
>>> +        dev_err(dev, "clocksource registration failed: %d\n", err);
>>> +        clk_disable_unprepare(ost->clk);
>>> +        return err;
>>> +    }
>>> +
>>> +    /* Cannot register a sched_clock with interrupts on */
>>
>> Aren't they already disabled?
> 
> Sorry for the late reply.
> 
> No, they are not already disabled; this is what I get if I comment out
> the local_irq_save()/local_irq_restore():
> 
> [    0.361014] clocksource: ingenic-ost: mask: 0xffffffff max_cycles:
> 0xffffffff, max_idle_ns: 159271703898 ns
> [    0.361515] clocksource: Switched to clocksource ingenic-ost
> [    0.361686] ------------[ cut here ]------------
> [    0.361893] WARNING: CPU: 0 PID: 1 at kernel/time/sched_clock.c:179
> sched_clock_register+0x7c/0x2e4
> [    0.362174] CPU: 0 PID: 1 Comm: swapper Not tainted 5.4.0-rc5+ #461
> [    0.362330] Stack : 80744558 80069b44 80770000 00000000 00000000
> 00dfd7a7 806e6db4 8106bb74
> [    0.362619]         806f0000 81067ca4 806f31c7 80769478 00000020
> 10000400 8106bb20 00dfd7a7
> [    0.362906]         00000000 00000000 80780000 00000000 00000007
> 00000001 00000049 3563722d
> [    0.363191]         8106ba61 00000000 ffffffff 00000010 806f0000
> 00000000 00000000 806f0000
> [    0.363477]         00000020 00000000 80714534 80770000 00000002
> 80319154 00000000 80770000
> [    0.363762]         ...
> [    0.363906] Call Trace:
> [    0.364087] [<8001af14>] show_stack+0x40/0x128
> [    0.364289] [<8002fd88>] __warn+0xb8/0xe0
> [    0.364478] [<8002fe14>] warn_slowpath_fmt+0x64/0xc0
> [    0.364678] [<8072b1c8>] sched_clock_register+0x7c/0x2e4
> [    0.364895] [<8073c874>] ingenic_ost_probe+0x224/0x248
> [    0.365090] [<803d5394>] platform_drv_probe+0x40/0x94
> [    0.365526] [<803d362c>] really_probe+0x104/0x374
> [    0.365743] [<803d3ff0>] device_driver_attach+0x78/0x80
> [    0.365938] [<803d4070>] __driver_attach+0x78/0x118
> [    0.366129] [<803d1700>] bus_for_each_dev+0x7c/0xc8
> [    0.366318] [<803d226c>] bus_add_driver+0x1bc/0x204
> [    0.366513] [<803d4878>] driver_register+0x84/0x14c
> [    0.366717] [<8073a144>] __platform_driver_probe+0x98/0x140
> [    0.366931] [<80724e38>] do_one_initcall+0x84/0x1b4
> [    0.367126] [<807250cc>] kernel_init_freeable+0x164/0x240
> [    0.367318] [<805df75c>] kernel_init+0x10/0xf8
> [    0.367510] [<8001542c>] ret_from_kernel_thread+0x14/0x1c
> [    0.367722] ---[ end trace 7fedf00408fa3bed ]---
> [    0.367985] sched_clock: 32 bits at 12MHz, resolution 83ns, wraps
> every 178956970966ns
> 
> At kernel/time/sched_clock.c:179 there is:
> WARN_ON(!irqs_disabled());

That is strange, no drivers is doing that and no warning is appearing.

Isn't missing a local_irq_disable in the code path in the stack above?

>>> +    local_irq_save(flags);
>>> +    if (soc_info->is64bit)
>>> +        sched_clock_register(ingenic_ost_read_cntl, 32, rate);
>>> +    else
>>> +        sched_clock_register(ingenic_ost_read_cnth, 32, rate);
>>> +    local_irq_restore(flags);
>>> +
>>> +    return 0;
>>> +}
>>> +


-- 
 <http://www.linaro.org/> Linaro.org │ Open source software for ARM SoCs

Follow Linaro:  <http://www.facebook.com/pages/Linaro> Facebook |
<http://twitter.com/#!/linaroorg> Twitter |
<http://www.linaro.org/linaro-blog/> Blog