linux-kernel - Re: [PATCH v3 3/4] input: misc: pm8941-pwrkey: add software key press debouncing support

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Date:   Thu, 3 Feb 2022 17:21:31 -0800
From:   Anjelique Melendez <quic_amelende@...cinc.com>
To:     Stephen Boyd <swboyd@...omium.org>, <dmitry.torokhov@...il.com>
CC:     <linux-input@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <linux-arm-msm@...r.kernel.org>, <collinsd@...eaurora.org>,
        <bjorn.andersson@...aro.org>, <skakit@...eaurora.org>
Subject: Re: [PATCH v3 3/4] input: misc: pm8941-pwrkey: add software key press
 debouncing support



On 2/3/2022 1:20 PM, Stephen Boyd wrote:
> Quoting Anjelique Melendez (2022-02-02 17:08:07)
>> From: David Collins <collinsd@...eaurora.org>
>>
>> On certain PMICs, an unexpected assertion of KPDPWR_DEB (the
>> positive logic hardware debounced power key signal) may be seen
>> during the falling edge of KPDPWR_N (i.e. a power key press) when
>> it occurs close to the rising edge of SLEEP_CLK.  This then
>> triggers a spurious KPDPWR interrupt.
>>
>> Handle this issue by adding software debouncing support to ignore
>> key events that occur within the hardware debounce delay after the
>> most recent key release event.
>>
>> Signed-off-by: David Collins <collinsd@...eaurora.org>
>> Signed-off-by: Anjelique Melendez <quic_amelende@...cinc.com>
>> ---
> 
> Is there a Fixes tag that should be here? Is it a new problem with newer
> PMICs?

There is no Fixes tag since this is a workaround for a HW bug. Yes, this is a relatively new problem
with the past few PMICs. Starting with PM8450, we need this workaround in pm8941-pwrkey
since we are no longer using an older downstream driver that had an equivalent work around.