linux-kernel - Re: [PATCH v3 2/3] Input: snvs_pwrkey

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Date:   Wed, 29 Jul 2020 23:04:26 -0700
From:   Dmitry Torokhov <dmitry.torokhov@...il.com>
To:     Marco Felsch <m.felsch@...gutronix.de>
Cc:     Horia Geantă <horia.geanta@....com>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        "David S. Miller" <davem@...emloft.net>,
        Rob Herring <robh+dt@...nel.org>,
        Shawn Guo <shawnguo@...nel.org>,
        André Draszik <git@...red.net>,
        Robin Gong <yibin.gong@....com>,
        Anson Huang <anson.huang@....com>,
        Fabio Estevam <festevam@...il.com>,
        Aymen Sghaier <aymen.sghaier@....com>,
        Adam Ford <aford173@...il.com>, linux-input@...r.kernel.org,
        linux-crypto@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, NXP Linux Team <linux-imx@....com>
Subject: Re: [PATCH v3 2/3] Input: snvs_pwrkey - enable snvs clock as needed

On Wed, Jul 29, 2020 at 09:33:23AM +0200, Marco Felsch wrote:
> Hi,
> 
> On 20-07-23 10:43, Horia Geantă wrote:
> > From: André Draszik <git@...red.net>
> > 
> > At the moment, enabling this driver without the SNVS RTC driver
> > being active will hang the kernel as soon as the power button
> > is pressed.
> > 
> > The reason is that in that case the SNVS isn't enabled, and
> > any attempt to read the SNVS registers will simply hang forever.
> > 
> > Ensure the clock is enabled (during the interrupt handler) to
> > make this driver work.
> > 
> > Also see commit 7f8993995410 ("drivers/rtc/rtc-snvs: add clock support")
> > and commit edb190cb1734
> > ("rtc: snvs: make sure clock is enabled for interrupt handle")
> > for similar updates to the snvs rtc driver.
> > 
> > Signed-off-by: André Draszik <git@...red.net>
> > Reviewed-by: Horia Geantă <horia.geanta@....com>
> > Signed-off-by: Horia Geantă <horia.geanta@....com>
> > ---
> >  drivers/input/keyboard/snvs_pwrkey.c | 28 +++++++++++++++++++++++++++-
> >  1 file changed, 27 insertions(+), 1 deletion(-)
> > 
> > diff --git a/drivers/input/keyboard/snvs_pwrkey.c b/drivers/input/keyboard/snvs_pwrkey.c
> > index 2f5e3ab5ed63..382d2ae82c9b 100644
> > --- a/drivers/input/keyboard/snvs_pwrkey.c
> > +++ b/drivers/input/keyboard/snvs_pwrkey.c
> > @@ -16,6 +16,7 @@
> >  #include <linux/of_address.h>
> >  #include <linux/platform_device.h>
> >  #include <linux/pm_wakeirq.h>
> > +#include <linux/clk.h>
> >  #include <linux/mfd/syscon.h>
> >  #include <linux/regmap.h>
> >  
> > @@ -38,6 +39,7 @@ struct pwrkey_drv_data {
> >  	int wakeup;
> >  	struct timer_list check_timer;
> >  	struct input_dev *input;
> > +	struct clk *clk;
> >  	u8 minor_rev;
> >  };
> >  
> > @@ -47,7 +49,10 @@ static void imx_imx_snvs_check_for_events(struct timer_list *t)
> >  	struct input_dev *input = pdata->input;
> >  	u32 state;
> >  
> > +	clk_enable(pdata->clk);
> >  	regmap_read(pdata->snvs, SNVS_HPSR_REG, &state);
> > +	clk_disable(pdata->clk);
> > +
> >  	state = state & SNVS_HPSR_BTN ? 1 : 0;
> >  
> >  	/* only report new event if status changed */
> > @@ -74,11 +79,13 @@ static irqreturn_t imx_snvs_pwrkey_interrupt(int irq, void *dev_id)
> >  
> >  	pm_wakeup_event(input->dev.parent, 0);
> >  
> > +	clk_enable(pdata->clk);
> > +
> >  	regmap_read(pdata->snvs, SNVS_LPSR_REG, &lp_status);
> >  	if (lp_status & SNVS_LPSR_SPO) {
> >  		if (pdata->minor_rev == 0) {
> >  			/*
> > -			 * The first generation i.MX6 SoCs only sends an
> > +			 * The first generation i.MX[6|7] SoCs only send an
> >  			 * interrupt on button release. To mimic power-key
> >  			 * usage, we'll prepend a press event.
> >  			 */
> > @@ -96,6 +103,8 @@ static irqreturn_t imx_snvs_pwrkey_interrupt(int irq, void *dev_id)
> >  	/* clear SPO status */
> >  	regmap_write(pdata->snvs, SNVS_LPSR_REG, SNVS_LPSR_SPO);
> >  
> > +	clk_disable(pdata->clk);
> 
> I'm not so happy about clk_enable/disable() during the interrupt
> routine since those routines should be handled fast. Since we assume
> that the clock is always oni

We do? I thought that the fact that clock might be off is the root of
the problem.

> I would rather call clk_prepare_enable()
> during probe() and keep the clock on.

clk_enable() must not sleep and is supposed to be lightweight. This
interrupt I believe is supposed to be infrequent, so having it here
should be fine and might save us some power.

> 
> > +
> >  	return IRQ_HANDLED;
> >  }
> >  
> > @@ -140,6 +149,23 @@ static int imx_snvs_pwrkey_probe(struct platform_device *pdev)
> >  	if (pdata->irq < 0)
> >  		return -EINVAL;
> >  
> > +	pdata->clk = devm_clk_get_optional(&pdev->dev, "snvs-pwrkey");
> > +	if (IS_ERR(pdata->clk))
> > +		return PTR_ERR(pdata->clk);
> > +
> > +	error = clk_prepare(pdata->clk);
> > +	if (error) {
> > +		dev_err(&pdev->dev, "failed to prepare the snvs clock\n");
> > +		return error;
> > +	}
> > +	error = devm_add_action_or_reset(&pdev->dev,
> > +			(void(*)(void *))clk_unprepare,
> > +			pdata->clk);
> 
> I'm not a fan about those casts. However, the intentation should be
> fixed.

Yes, can we please create a proper function for this (or maybe we will
finally get devm clk API?).

Thanks.

-- 
Dmitry