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Date:   Sun, 9 Feb 2020 14:38:36 -0800
From:   Dmitry Torokhov <dmitry.torokhov@gmail.com>
To:     Horia Geanta <horia.geanta@nxp.com>
Cc:     =?iso-8859-1?Q?Andr=E9?= Draszik <git@andred.net>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Anson Huang <anson.huang@nxp.com>,
        Aymen Sghaier <aymen.sghaier@nxp.com>,
        Herbert Xu <herbert@gondor.apana.org.au>,
        "David S. Miller" <davem@davemloft.net>,
        Rob Herring <robh+dt@kernel.org>,
        Mark Rutland <mark.rutland@arm.com>,
        "linux-crypto@vger.kernel.org" <linux-crypto@vger.kernel.org>,
        "devicetree@vger.kernel.org" <devicetree@vger.kernel.org>,
        "linux-input@vger.kernel.org" <linux-input@vger.kernel.org>,
        Robin Gong <yibin.gong@nxp.com>,
        dl-linux-imx <linux-imx@nxp.com>
Subject: Re: [PATCH 2/3] Input: snvs_pwrkey - enable snvs clock as needed
Message-ID: <20200209223836.GA199269@dtor-ws>
References: <20200130204516.4760-1-git@andred.net>
 <20200130204516.4760-2-git@andred.net>
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On Fri, Feb 07, 2020 at 08:10:22AM +0000, Horia Geanta wrote:
> On 1/30/2020 10:45 PM, André Draszik wrote:
> > 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@andred.net>
> > Cc: Anson Huang <Anson.Huang@nxp.com>
> > Cc: Dmitry Torokhov <dmitry.torokhov@gmail.com>
> > Cc: "Horia Geantă" <horia.geanta@nxp.com>
> > Cc: Aymen Sghaier <aymen.sghaier@nxp.com>
> > Cc: Herbert Xu <herbert@gondor.apana.org.au>
> > Cc: "David S. Miller" <davem@davemloft.net>
> > Cc: Rob Herring <robh+dt@kernel.org>
> > Cc: Mark Rutland <mark.rutland@arm.com>
> > Cc: linux-crypto@vger.kernel.org
> > Cc: devicetree@vger.kernel.org
> > Cc: linux-input@vger.kernel.org
> > ---
> >  drivers/input/keyboard/snvs_pwrkey.c | 27 +++++++++++++++++++++++++++
> >  1 file changed, 27 insertions(+)
> > 
> > diff --git a/drivers/input/keyboard/snvs_pwrkey.c b/drivers/input/keyboard/snvs_pwrkey.c
> > index 2f5e3ab5ed63..c29711d8735c 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;
> >  };
> >  
> > @@ -72,6 +74,9 @@ static irqreturn_t imx_snvs_pwrkey_interrupt(int irq, void *dev_id)
> >  	struct input_dev *input = pdata->input;
> >  	u32 lp_status;
> >  
> > +	if (pdata->clk)
> > +		clk_enable(pdata->clk);
> > +
> clk framework handles NULL pointers internally, the check is redundant.
> 
> >  	pm_wakeup_event(input->dev.parent, 0);
> >  
> >  	regmap_read(pdata->snvs, SNVS_LPSR_REG, &lp_status);
> > @@ -96,6 +101,9 @@ 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);
> >  
> > +	if (pdata->clk)
> > +		clk_disable(pdata->clk);
> > +
> >  	return IRQ_HANDLED;
> >  }
> >  
> > @@ -140,6 +148,25 @@ static int imx_snvs_pwrkey_probe(struct platform_device *pdev)
> >  	if (pdata->irq < 0)
> >  		return -EINVAL;
> >  
> > +	pdata->clk = devm_clk_get(&pdev->dev, "snvs-pwrkey");
> > +	if (IS_ERR(pdata->clk)) {
> > +		pdata->clk = NULL;
> Using devm_clk_get_optional() would simplify error handling.

It sounds to me that this clock is not at all optional and the driver
currently "works" only by accident and therefore optional is not
suitable here.

> 
> > +	} else {
> > +		error = clk_prepare_enable(pdata->clk);

So if you enable clock here and do not disable it, why do you need to
enable it again in interrupt?

Thanks.

-- 
Dmitry