From: Hans de Goede <hdegoede@redhat.com>
To: Andy Shevchenko <andy.shevchenko@gmail.com>
Cc: Shyam Sundar S K <Shyam-sundar.S-k@amd.com>,
Linus Walleij <linus.walleij@linaro.org>,
Coiby Xu <coiby.xu@gmail.com>, wang jun <availa@outlook.com>,
"open list:GPIO SUBSYSTEM" <linux-gpio@vger.kernel.org>,
linux-kernel-mentees@lists.linuxfoundation.org,
Nehal Shah <Nehal-bakulchandra.Shah@amd.com>
Subject: Re: [Linux-kernel-mentees] Any other ways to debug GPIO interrupt controller (pinctrl-amd) for broken touchpads of a new laptop model?
Date: Tue, 3 Nov 2020 12:00:34 +0100 [thread overview]
Message-ID: <6a8a246b-1b11-f569-b495-6440e70fc121@redhat.com> (raw)
In-Reply-To: <CAHp75VdYhe4YEAzULMNkhihTQwHAP3fC2F6iD=datqzyzd=4fQ@mail.gmail.com>
Hi,
On 11/3/20 11:49 AM, Andy Shevchenko wrote:
> On Tue, Nov 3, 2020 at 12:12 PM Hans de Goede <hdegoede@redhat.com> wrote:
>> On 11/3/20 1:05 AM, Coiby Xu wrote:
>>> On Tue, Oct 27, 2020 at 11:09:11AM +0100, Hans de Goede wrote:
>
> ...
>
>>> [1] https://lore.kernel.org/patchwork/comment/1522675/
>>
>> This is a case where Andy is obviously right and you should just use the
>> higher precision "unit = 15625" value (except probably that is wrong too,
>> see below).
>>
>> We have had similar issues with the docs for getting the TSC frequency
>> on some Intel chips, where the docs said 16.6 MHz for a certain register
>> value, where what they meant was 100/6 MHz which really is significantly
>> different. This was leading to a time drift of 5 minutes / day on non
>> networked (so no NTP) Linux systems.
>>
>> I think this is what Andy was referring to when he wrote:
>> "What the heck with HW companies! (Just an emotion based on the experience)"
>
> Exactly!
>
> ...
>
>> Actually all the values look somewhat suspect. The comment:
>>
>>> Debounce Debounce Timer Max
>>> TmrLarge TmrOutUnit Unit Debounce
>>> Time
>>> 0 0 61 usec (2 RtcClk) 976 usec
>>> 0 1 244 usec (8 RtcClk) 3.9 msec
>>> 1 0 15.6 msec (512 RtcClk) 250 msec
>>> 1 1 62.5 msec (2048 RtcClk) 1 sec
>>
>> Helpfully gives the values in RtcClks. A typical RTC clock crystal
>> is 32 KHz which gives us 31.25 usec per tick, so I would expect the
>> values to be:
>
> I guess you are mistaken here. Usual frequency for RTC is 32.768kHz
> [1], which gives more or less above values
>
> 30.51757
> 61.03515
> 244.14062
> 15625
> 62500
You are completely right, my bad.
> [1]: https://en.wikipedia.org/wiki/Real-time_clock
> (just google: rtc clock frequency)
I did duckduckgo, but one of the first hits said 32KHz crystal and
I assumed that meant 32.000 KHz falling into the exact precision
trap I was complaining about in my previous email, oops.
Regards,
Hans
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next prev parent reply other threads:[~2020-11-03 11:00 UTC|newest]
Thread overview: 42+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-10-01 13:22 [Linux-kernel-mentees] Any other ways to debug GPIO interrupt controller (pinctrl-amd) for broken touchpads of a new laptop model? Coiby Xu
2020-10-01 20:57 ` Linus Walleij
2020-10-02 9:40 ` Hans de Goede
2020-10-02 12:42 ` Coiby Xu
2020-10-02 13:36 ` Hans de Goede
2020-10-02 14:51 ` Coiby Xu
2020-10-02 19:44 ` Hans de Goede
2020-10-02 22:45 ` Coiby Xu
2020-10-03 13:22 ` Hans de Goede
2020-10-03 23:03 ` Coiby Xu
2020-10-04 5:16 ` Coiby Xu
2020-10-06 4:49 ` Coiby Xu
2020-10-06 6:28 ` Hans de Goede
2020-10-06 8:31 ` Coiby Xu
2020-10-06 8:55 ` Hans de Goede
2020-10-06 9:28 ` Hans de Goede
2020-10-06 9:29 ` Hans de Goede
2020-10-08 16:32 ` Coiby Xu
2020-10-14 4:24 ` Coiby Xu
2020-10-14 11:34 ` Coiby Xu
2020-10-14 11:46 ` Hans de Goede
2020-10-15 3:27 ` Coiby Xu
2020-10-15 4:06 ` Coiby Xu
2020-10-26 22:54 ` Coiby Xu
2020-10-27 9:52 ` Andy Shevchenko
2020-10-30 4:58 ` Coiby Xu
2020-10-27 10:09 ` Hans de Goede
2020-10-27 15:13 ` Andy Shevchenko
2020-10-27 16:00 ` Hans de Goede
2020-10-27 16:09 ` Andy Shevchenko
2020-10-29 8:04 ` Mika Westerberg
2020-10-30 4:54 ` Coiby Xu
2020-11-02 19:06 ` Andy Shevchenko
2020-11-02 22:56 ` Coiby Xu
2020-11-03 0:05 ` Coiby Xu
2020-11-03 10:12 ` Hans de Goede
2020-11-03 10:49 ` Andy Shevchenko
2020-11-03 11:00 ` Hans de Goede [this message]
2020-10-08 16:26 ` Coiby Xu
2020-10-06 9:16 ` Linus Walleij
2020-10-08 16:40 ` Coiby Xu
2020-10-02 10:59 ` Coiby Xu
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