[Linux-kernel-mentees] Any other ways to debug GPIO interrupt controller (pinctrl-amd) for broken touchpads of a new laptop model?
Hans de Goede
hdegoede at redhat.com
Tue Nov 3 11:00:34 UTC 2020
On 11/3/20 11:49 AM, Andy Shevchenko wrote:
> On Tue, Nov 3, 2020 at 12:12 PM Hans de Goede <hdegoede at 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:
>>>  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)"
>> Actually all the values look somewhat suspect. The comment:
>>> Debounce Debounce Timer Max
>>> TmrLarge TmrOutUnit Unit Debounce
>>> 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
> , which gives more or less above values
You are completely right, my bad.
> : 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.
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