linux-kernel - Re: [PATCH 02/17] clocksource: davinci-timer: new driver

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Date:   Thu, 24 Jan 2019 17:39:19 +0530
From:   Sekhar Nori <nsekhar@...com>
To:     Bartosz Golaszewski <brgl@...ev.pl>
CC:     Kevin Hilman <khilman@...nel.org>,
        Daniel Lezcano <daniel.lezcano@...aro.org>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        devicetree <devicetree@...r.kernel.org>,
        Bartosz Golaszewski <bgolaszewski@...libre.com>
Subject: Re: [PATCH 02/17] clocksource: davinci-timer: new driver

On 17/01/19 7:31 PM, Bartosz Golaszewski wrote:
> czw., 17 sty 2019 o 13:42 Sekhar Nori <nsekhar@...com> napisał(a):
>>
>> On 16/01/19 2:48 PM, Sekhar Nori wrote:
>>> On 14/01/19 10:09 PM, Bartosz Golaszewski wrote:
>>>> pon., 14 sty 2019 o 13:20 Sekhar Nori <nsekhar@...com> napisał(a):
>>>>>
>>>>> Hi Bartosz,
>>>>>
>>>>> On 11/01/19 10:51 PM, Bartosz Golaszewski wrote:
>>>>>> From: Bartosz Golaszewski <bgolaszewski@...libre.com>
>>>>>>
>>>>>> Currently the clocksource and clockevent support for davinci platforms
>>>>>> lives in mach-davinci. It hard-codes many things, used global variables,
>>>>>> implements functionalities unused by any platform and has code fragments
>>>>>> scattered across many (often unrelated) files.
>>>>>>
>>>>>> Implement a new, modern and simplified timer driver and put it into
>>>>>> drivers/clocksource. We still need to support legacy board files so
>>>>>> export a config structure and a function that allows machine code to
>>>>>> register the timer.
>>>>>>
>>>>>> We don't check the return values of regmap reads and writes since with
>>>>>> mmio it's only likely to fail due to programmer's errors.
>>>>>>
>>>>>> We also don't bother freeing resources on errors in
>>>>>> davinci_timer_register() as the system won't boot without a timer anyway.
>>>>>>
>>>>>> Signed-off-by: Bartosz Golaszewski <bgolaszewski@...libre.com>
>>>>>
>>>>> With this series, DA830 fails to boot. Rest of the devices are okay from
>>>>> boot perspective.
>>>>>
>>>>> DA830 is pretty unique because it uses the same timer-half for both
>>>>> clocksource and clockevent. May be you can set the same configuration on
>>>>> your DA850 to see the same issue? Else, I will enable low-level debug
>>>>> and try to provide more debug data.
>>>>>
>>>>
>>>> I can't boot da850 with the same config as da830 (0x60 compare
>>>> register, compare irq 74) even with the old timer code. Just to make
>>>> sure: does da830 boot fine with mainline v5.0-rc2?
>>>
>>> Yeah, I did check that without the patch DA830 does boot.
>>
>> You are right that DA850 lacks compare interrupts for timers 0 and 1.
>> So, yes, it seems like we will have to shift to timer2 to test
>> compare interrupts on DA850.
>>
> 
> Timers 2 and 3 are a bit different on da850 - for instance they don't
> have separate interrupts for bottom and top halfs.

We should only be using the compare feature which has a a separate
interrupt (distinct from top and bottom half interrupts). Only timer 2
and 3 of DA850 have the compare interrupts though. So you will have to
use those timers to be able to test compare feature on DA850.

> 
> I configured the old code to use timer 2 - bottom half only with
> compare register 0x60 and compare intterupt 74. It boots although very
> slowly and something's broken with timekeeping as the clock goes
> backwards and forward (seemingly) randomly.

Ah, okay. Timer 2/3 use ASYNC3 as clock input instead of PLL0_AUXCLK.
Did you make adjustment for this too?

> 
> Kevin has an OMAP-L137 starter kit - is this the same as da830-evm? If

Yes.

> so, then I can get remote access to it and work on this problem.
> Otherwise, I can prepare something that works on da850 with broken
> timekeeping and let you see if it works correctly on da830.

Alright, happy to test.

Thanks,
Sekhar