linux-kernel - Re: [PATCH v2 1/1] iio: imx8qxp-adc: fix irq flood when call imx8qxp_adc_read

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Message-ID: <20221202090554.GA10754@chq-T47>
Date:   Fri, 2 Dec 2022 17:05:54 +0800
From:   Cai Huoqing <cai.huoqing@...ux.dev>
To:     Bough Chen <haibo.chen@....com>
Cc:     Frank Li <frank.li@....com>,
        "festevam@...il.com" <festevam@...il.com>,
        "imx@...ts.linux.dev" <imx@...ts.linux.dev>,
        "jic23@...nel.org" <jic23@...nel.org>,
        "kernel@...gutronix.de" <kernel@...gutronix.de>,
        "lars@...afoo.de" <lars@...afoo.de>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-iio@...r.kernel.org" <linux-iio@...r.kernel.org>,
        dl-linux-imx <linux-imx@....com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "s.hauer@...gutronix.de" <s.hauer@...gutronix.de>,
        "shawnguo@...nel.org" <shawnguo@...nel.org>
Subject: Re: [PATCH v2 1/1] iio: imx8qxp-adc: fix irq flood when call
 imx8qxp_adc_read_raw()

On 02 12月 22 03:23:55, Bough Chen wrote:
> > -----Original Message-----
> > From: Frank Li <frank.li@....com>
> > Sent: 2022年12月1日 22:01
> > To: Bough Chen <haibo.chen@....com>
> > Cc: cai.huoqing@...ux.dev; festevam@...il.com; Frank Li <frank.li@....com>;
> > imx@...ts.linux.dev; jic23@...nel.org; kernel@...gutronix.de;
> > lars@...afoo.de; linux-arm-kernel@...ts.infradead.org;
> > linux-iio@...r.kernel.org; dl-linux-imx <linux-imx@....com>;
> > linux-kernel@...r.kernel.org; s.hauer@...gutronix.de; shawnguo@...nel.org
> > Subject: [PATCH v2 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@...r.kernel.org
> > 
> > Signed-off-by: Frank Li <Frank.Li@....com>
> 
> Thanks for the quick fix. The total read count in irq handler is fifo_count which is read from register, this is reasonable.
> 
> Reviewed-by: Haibo Chen <haibo.chen@....com>
The same, thanks.
Reviewed-by: Cai Huoqing <cai.huoqing@...ux.dev>
> 
> Best Regards
> Haibo Chen
> > ---
> > Change from v1 to v2
> >  - move complete() after read fifo
> > 
> > 
> >  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-adc.c index
> > 36777b827165..f5a0fc9e64c5 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 = FIELD_GET(IMX8QXP_ADC_RESFIFO_VAL_MASK,
> > -				 readl(adc->regs + IMX8QXP_ADR_ADC_RESFIFO));
> > +		*val = adc->fifo[0];
> > 
> >  		mutex_unlock(&adc->lock);
> >  		return IIO_VAL_INT;
> > @@ -265,10 +267,15 @@ static irqreturn_t imx8qxp_adc_isr(int irq, void
> > *dev_id)  {
> >  	struct imx8qxp_adc *adc = dev_id;
> >  	u32 fifo_count;
> > +	int i;
> > 
> >  	fifo_count = FIELD_GET(IMX8QXP_ADC_FCTRL_FCOUNT_MASK,
> >  			       readl(adc->regs + IMX8QXP_ADR_ADC_FCTRL));
> > 
> > +	for (i = 0; i < fifo_count; i++)
> > +		adc->fifo[i] = FIELD_GET(IMX8QXP_ADC_RESFIFO_VAL_MASK,
> > +				readl_relaxed(adc->regs + IMX8QXP_ADR_ADC_RESFIFO));
> > +
> >  	if (fifo_count)
> >  		complete(&adc->completion);
> > 
> > --
> > 2.34.1
>