Re: Any other ways to debug GPIO interrupt controller (pinctrl-amd) for broken touchpads of a new laptop model?

From: Hans de Goede <hdegoede@redhat.com>
To: Andy Shevchenko <andy.shevchenko@gmail.com>
Cc: Coiby Xu <coiby.xu@gmail.com>,
	Linus Walleij <linus.walleij@linaro.org>,
	"open list:GPIO SUBSYSTEM" <linux-gpio@vger.kernel.org>,
	wang jun <availa@outlook.com>,
	Nehal Shah <Nehal-bakulchandra.Shah@amd.com>,
	Shyam Sundar S K <Shyam-sundar.S-k@amd.com>,
	linux-kernel-mentees@lists.linuxfoundation.org
Subject: Re: 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