Subject: Re: [PATCH v3] input: keyboard: snvs_pwrkey: Send key events for i.MX6 S, DL and Q

From: Dmitry Torokhov <[email-masked]>
Date: Mon, 16 Sep 2019 16:37:01 -0700

On Mon, Sep 16, 2019 at 07:45:37AM +0000, Robin Gong wrote:
> On 2019/9/13 15:31 robin <[email-masked]> wrote:> 
> > Hi Dmitry,
> > 
> > On 2019-09-12 22:13, Dmitry Torokhov wrote:
> > > Hi Robin,
> > >
> > > On Wed, Sep 04, 2019 at 06:23:29AM +0000, Robin van der Gracht wrote:
> > >> The first generation i.MX6 processors does not send an interrupt when
> > >> the power key is pressed. It sends a power down request interrupt if
> > >> the key is released before a hard shutdown (5 second press). This
> > >> should allow software to bring down the SoC safely.
> > >>
> > >> For this driver to work as a regular power key with the older SoCs,
> > >> we need to send a keypress AND release when we get the power down
> > >> request irq.
> > >>
> > >> Signed-off-by: Robin van der Gracht <[email-masked]>
> > >> ---
> > >> @@ -67,13 +83,17 @@ static irqreturn_t imx_snvs_pwrkey_interrupt(int
> > >> irq, void *dev_id)  {
> > >>  	struct platform_device *pdev = dev_id;
> > >>  	struct pwrkey_drv_data *pdata = platform_get_drvdata(pdev);
> > >> +	unsigned long expire = jiffies;
> > >>  	u32 lp_status;
> > >>
> > >>  	pm_wakeup_event(pdata->input->dev.parent, 0);
> > >>
> > >>  	regmap_read(pdata->snvs, SNVS_LPSR_REG, &lp_status);
> > >> -	if (lp_status & SNVS_LPSR_SPO)
> > >> -		mod_timer(&pdata->check_timer, jiffies +
> > >> msecs_to_jiffies(DEBOUNCE_TIME));
> > >> +	if (lp_status & SNVS_LPSR_SPO) {
> > >> +		if (pdata->minor_rev > 0)
> > >> +			expire = jiffies + msecs_to_jiffies(DEBOUNCE_TIME);
> > >> +		mod_timer(&pdata->check_timer, expire);
> > >
> > > Why do we even need to fire the timer in case of the first generation
> > > hardware? Just send press and release events directly from the ISR.
> That timer looks like a software debounce to prevent unexpected and
> meaningless interrupt/event caused by quick press/release.   

Right, but in case of the first generation hardware we schedule the
timer immediately (expire == 0) and do not check state of the hardware
in the timer handler, but rather simply emit down/up events, so we do
not really get any benefit from the timer (again, I am talking about
first generation hardware only).

Thanks.

-- 
Dmitry

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