linux-kernel - Re: [PATCH] [v2] clocksource/drivers/npcm: fix GENMASK and timer operation

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Date:   Mon, 15 Jul 2019 18:48:05 +0300
From:   Avi Fishman <avifishman70@...il.com>
To:     Joe Perches <joe@...ches.com>
Cc:     Tomer Maimon <tmaimon77@...il.com>,
        Tali Perry <tali.perry1@...il.com>,
        Patrick Venture <venture@...gle.com>,
        Nancy Yuen <yuenn@...gle.com>,
        Benjamin Fair <benjaminfair@...gle.com>,
        Daniel Lezcano <daniel.lezcano@...aro.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        OpenBMC Maillist <openbmc@...ts.ozlabs.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] [v2] clocksource/drivers/npcm: fix GENMASK and timer operation

On Mon, Jul 15, 2019 at 6:25 PM Joe Perches <joe@...ches.com> wrote:
>
> On Mon, 2019-07-15 at 18:19 +0300, Avi Fishman wrote:
> > clocksource/drivers/npcm: fix GENMASK and timer operation
> >
> > NPCM7XX_Tx_OPER GENMASK() changed from (27, 3) to (28, 27)
> >
> > in npcm7xx_timer_oneshot() the original NPCM7XX_REG_TCSR0 register was
> > read again after masking it with ~NPCM7XX_Tx_OPER so the masking didn't
> > take effect.
> >
> > npcm7xx_timer_periodic() was not wrong but it wrote to NPCM7XX_REG_TICR0
> > in a middle of read modify write to NPCM7XX_REG_TCSR0 which is
> > confusing.
>
> You might mention how the original use of GENMASK(3, 27)
> was defective or correct without effect.

Done, see v3 of this patch.

>
> > Signed-off-by: Avi Fishman <avifishman70@...il.com>
> > ---
> >  drivers/clocksource/timer-npcm7xx.c | 9 +++------
> >  1 file changed, 3 insertions(+), 6 deletions(-)
> >
> > diff --git a/drivers/clocksource/timer-npcm7xx.c
> > b/drivers/clocksource/timer-npcm7xx.c
> > index 8a30da7f083b..9780ffd8010e 100644
> > --- a/drivers/clocksource/timer-npcm7xx.c
> > +++ b/drivers/clocksource/timer-npcm7xx.c
> > @@ -32,7 +32,7 @@
> >  #define NPCM7XX_Tx_INTEN               BIT(29)
> >  #define NPCM7XX_Tx_COUNTEN             BIT(30)
> >  #define NPCM7XX_Tx_ONESHOT             0x0
> > -#define NPCM7XX_Tx_OPER                        GENMASK(27, 3)
> > +#define NPCM7XX_Tx_OPER                        GENMASK(28, 27)
> >  #define NPCM7XX_Tx_MIN_PRESCALE                0x1
> >  #define NPCM7XX_Tx_TDR_MASK_BITS       24
> >  #define NPCM7XX_Tx_MAX_CNT             0xFFFFFF
> > @@ -84,8 +84,6 @@ static int npcm7xx_timer_oneshot(struct
> > clock_event_device *evt)
> >
> >         val = readl(timer_of_base(to) + NPCM7XX_REG_TCSR0);
> >         val &= ~NPCM7XX_Tx_OPER;
> > -
> > -       val = readl(timer_of_base(to) + NPCM7XX_REG_TCSR0);
> >         val |= NPCM7XX_START_ONESHOT_Tx;
> >         writel(val, timer_of_base(to) + NPCM7XX_REG_TCSR0);
> >
> > @@ -97,12 +95,11 @@ static int npcm7xx_timer_periodic(struct
> > clock_event_device *evt)
> >         struct timer_of *to = to_timer_of(evt);
> >         u32 val;
> >
> > +       writel(timer_of_period(to), timer_of_base(to) + NPCM7XX_REG_TICR0);
> > +
> >         val = readl(timer_of_base(to) + NPCM7XX_REG_TCSR0);
> >         val &= ~NPCM7XX_Tx_OPER;
> > -
> > -       writel(timer_of_period(to), timer_of_base(to) + NPCM7XX_REG_TICR0);
> >         val |= NPCM7XX_START_PERIODIC_Tx;
> > -
> >         writel(val, timer_of_base(to) + NPCM7XX_REG_TCSR0);
> >
> >         return 0;
> >
>


-- 
Regards,
Avi