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From:   Frank Li <frank.li@nxp.com>
To:     Bough Chen <haibo.chen@nxp.com>,
        Cai Huoqing <cai.huoqing@linux.dev>,
        Jonathan Cameron <jic23@kernel.org>,
        Lars-Peter Clausen <lars@metafoo.de>,
        Shawn Guo <shawnguo@kernel.org>,
        Sascha Hauer <s.hauer@pengutronix.de>,
        Pengutronix Kernel Team <kernel@pengutronix.de>,
        Fabio Estevam <festevam@gmail.com>,
        dl-linux-imx <linux-imx@nxp.com>,
        "open list:NXP i.MX 8QXP ADC DRIVER" <linux-iio@vger.kernel.org>,
        "moderated list:ARM/FREESCALE IMX / MXC ARM ARCHITECTURE" 
        <linux-arm-kernel@lists.infradead.org>,
        open list <linux-kernel@vger.kernel.org>
CC:     "imx@lists.linux.dev" <imx@lists.linux.dev>
Subject: RE: [PATCH 1/1] iio: imx8qxp-adc: fix irq flood when call
 imx8qxp_adc_read_raw()
Thread-Topic: [PATCH 1/1] iio: imx8qxp-adc: fix irq flood when call
 imx8qxp_adc_read_raw()
Thread-Index: AQHZBBITIcbXLdLL4k6c7baUCCsSgK5WG9cAgAEggQCAAEUfsA==
Date:   Wed, 30 Nov 2022 14:09:00 +0000
Message-ID: <HE1PR0401MB23316F98F160D737F07D7E4A88159@HE1PR0401MB2331.eurprd04.prod.outlook.com>
References: <20221129164531.2164660-1-Frank.Li@nxp.com>
 <20221129164531.2164660-2-Frank.Li@nxp.com>
 <DB7PR04MB401094B273FB9F851CE9A06190159@DB7PR04MB4010.eurprd04.prod.outlook.com>
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> -----Original Message-----
> From: Bough Chen <haibo.chen@nxp.com>
> Sent: Wednesday, November 30, 2022 3:58 AM
> To: Frank Li <frank.li@nxp.com>; Cai Huoqing <cai.huoqing@linux.dev>;
> Jonathan Cameron <jic23@kernel.org>; Lars-Peter Clausen
> <lars@metafoo.de>; Shawn Guo <shawnguo@kernel.org>; Sascha Hauer
> <s.hauer@pengutronix.de>; Pengutronix Kernel Team
> <kernel@pengutronix.de>; Fabio Estevam <festevam@gmail.com>; dl-linux-
> imx <linux-imx@nxp.com>; open list:NXP i.MX 8QXP ADC DRIVER <linux-
> iio@vger.kernel.org>; moderated list:ARM/FREESCALE IMX / MXC ARM
> ARCHITECTURE <linux-arm-kernel@lists.infradead.org>; open list <linux-
> kernel@vger.kernel.org>
> Cc: imx@lists.linux.dev
> Subject: RE: [PATCH 1/1] iio: imx8qxp-adc: fix irq flood when call
> imx8qxp_adc_read_raw()
>=20
> > -----Original Message-----
> > From: Frank Li <frank.li@nxp.com>
> > Sent: 2022=1B$BG/=1B(B11=1B$B7n=1B(B30=1B$BF|=1B(B 0:46
> > To: Cai Huoqing <cai.huoqing@linux.dev>; Bough Chen
> <haibo.chen@nxp.com>;
> > Jonathan Cameron <jic23@kernel.org>; Lars-Peter Clausen
> <lars@metafoo.de>;
> > Shawn Guo <shawnguo@kernel.org>; Sascha Hauer
> <s.hauer@pengutronix.de>;
> > Pengutronix Kernel Team <kernel@pengutronix.de>; Fabio Estevam
> > <festevam@gmail.com>; dl-linux-imx <linux-imx@nxp.com>; open list:NXP
> i.MX
> > 8QXP ADC DRIVER <linux-iio@vger.kernel.org>; moderated
> > list:ARM/FREESCALE IMX / MXC ARM ARCHITECTURE
> > <linux-arm-kernel@lists.infradead.org>; open list <linux-
> kernel@vger.kernel.org>
> > Cc: imx@lists.linux.dev
> > Subject: [PATCH 1/1] iio: imx8qxp-adc: fix irq flood when call
> > imx8qxp_adc_read_raw()
> >
> > irq flood happen when run
> >     cat /sys/bus/iio/devices/iio:device0/in_voltage1_raw
> >
> > imx8qxp_adc_read_raw()
> > {
> > 	...
> > 	enable irq
> > 	/* adc start */
> > 	writel(1, adc->regs + IMX8QXP_ADR_ADC_SWTRIG);
> > 	^^^^ trigger irq flood.
> > 	wait_for_completion_interruptible_timeout();
> > 	readl(adc->regs + IMX8QXP_ADR_ADC_RESFIFO);
> > 	^^^^ clear irq here.
> > 	...
> > }
> >
> > There is only FIFO watermark interrupt at this ADC controller.
> > IRQ line will be assert until software read data from FIFO.
> > So IRQ flood happen during wait_for_completion_interruptible_timeout().
> >
> > Move FIFO read into irq handle to avoid irq flood.
> >
> > Fixes: 1e23dcaa1a9f ("iio: imx8qxp-adc: Add driver support for NXP
> IMX8QXP
> > ADC")
> > Cc: stable@vger.kernel.org
> >
> > Signed-off-by: Frank Li <Frank.Li@nxp.com>
> > ---
> >  drivers/iio/adc/imx8qxp-adc.c | 11 +++++++++--
> >  1 file changed, 9 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/iio/adc/imx8qxp-adc.c b/drivers/iio/adc/imx8qxp-ad=
c.c
> index
> > 36777b827165..3cfba5c0fa34 100644
> > --- a/drivers/iio/adc/imx8qxp-adc.c
> > +++ b/drivers/iio/adc/imx8qxp-adc.c
> > @@ -86,6 +86,8 @@
> >
> >  #define IMX8QXP_ADC_TIMEOUT		msecs_to_jiffies(100)
> >
> > +#define IMX8QXP_ADC_MAX_FIFO_SIZE		16
> > +
> >  struct imx8qxp_adc {
> >  	struct device *dev;
> >  	void __iomem *regs;
> > @@ -95,6 +97,7 @@ struct imx8qxp_adc {
> >  	/* Serialise ADC channel reads */
> >  	struct mutex lock;
> >  	struct completion completion;
> > +	u32 fifo[IMX8QXP_ADC_MAX_FIFO_SIZE];
> >  };
> >
> >  #define IMX8QXP_ADC_CHAN(_idx) {				\
> > @@ -238,8 +241,7 @@ static int imx8qxp_adc_read_raw(struct iio_dev
> > *indio_dev,
> >  			return ret;
> >  		}
> >
> > -		*val =3D FIELD_GET(IMX8QXP_ADC_RESFIFO_VAL_MASK,
> > -				 readl(adc->regs +
> IMX8QXP_ADR_ADC_RESFIFO));
> > +		*val =3D adc->fifo[0];
> >
> >  		mutex_unlock(&adc->lock);
> >  		return IIO_VAL_INT;
> > @@ -265,6 +267,7 @@ static irqreturn_t imx8qxp_adc_isr(int irq, void
> *dev_id)
> > {
> >  	struct imx8qxp_adc *adc =3D dev_id;
> >  	u32 fifo_count;
> > +	int i;
> >
> >  	fifo_count =3D FIELD_GET(IMX8QXP_ADC_FCTRL_FCOUNT_MASK,
> >  			       readl(adc->regs + IMX8QXP_ADR_ADC_FCTRL));
> @@
> > -272,6 +275,10 @@ static irqreturn_t imx8qxp_adc_isr(int irq, void *dev=
_id)
> >  	if (fifo_count)
> >  		complete(&adc->completion);
> >
> > +	for (i =3D 0; i < fifo_count; i++)
> > +		adc->fifo[i] =3D FIELD_GET(IMX8QXP_ADC_RESFIFO_VAL_MASK,
> > +				readl_relaxed(adc->regs +
> IMX8QXP_ADR_ADC_RESFIFO));
>=20
> Hi Frank,
>=20
> Since the ADC mode is config as single-ended 12-bit conversion, every tim=
e
> when trigger the ADC conversion, only one 12-bit data push into fifo.
> And we also config the fifo watermark as 1. So here only need to read onc=
e. I
> already confirmed on my board.

Interrupt handle should guarantee read all data from FIFO.  If somewhere in=
crease
Watermark or set auto continue sample,  irq flood will be happen again.

Best regards
Frank Li=20

>=20
> Best Regards
> Haibo Chen
> > +
> >  	return IRQ_HANDLED;
> >  }
> >
> > --
> > 2.34.1