linux-kernel - RE: [PATCH V4 2/2] timer: imx-tpm: add imx tpm timer support

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Message-ID: <AM3PR04MB30696395B2A14D71FA6193780B30@AM3PR04MB306.eurprd04.prod.outlook.com>
Date:   Tue, 1 Aug 2017 03:33:15 +0000
From:   "A.s. Dong" <aisheng.dong@....com>
To:     Daniel Lezcano <daniel.lezcano@...aro.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
CC:     "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "tglx@...utronix.de" <tglx@...utronix.de>,
        "shawnguo@...nel.org" <shawnguo@...nel.org>,
        Jacky Bai <ping.bai@....com>,
        Anson Huang <anson.huang@....com>,
        "dongas86@...il.com" <dongas86@...il.com>,
        "kernel@...gutronix.de" <kernel@...gutronix.de>,
        "Arnd Bergmann" <arnd@...db.de>
Subject: RE: [PATCH V4 2/2] timer: imx-tpm: add imx tpm timer support

Hi Daniel,

> -----Original Message-----
> From: Daniel Lezcano [mailto:daniel.lezcano@...aro.org]
> Sent: Monday, July 31, 2017 10:29 PM
> To: A.s. Dong; linux-kernel@...r.kernel.org
> Cc: linux-arm-kernel@...ts.infradead.org; tglx@...utronix.de;
> shawnguo@...nel.org; Jacky Bai; Anson Huang; dongas86@...il.com;
> kernel@...gutronix.de; Arnd Bergmann
> Subject: Re: [PATCH V4 2/2] timer: imx-tpm: add imx tpm timer support
> 
> On 05/07/2017 04:35, Dong Aisheng wrote:
> > IMX Timer/PWM Module (TPM) supports both timer and pwm function while
> > this patch only adds the timer support. PWM would be added later.
> >
> > The TPM counter, compare and capture registers are clocked by an
> > asynchronous clock that can remain enabled in low power modes.
> >
> > NOTE: We observed in a very small probability, the bus fabric
> > contention between GPU and A7 may results a few cycles delay of
> > writing CNT registers which may cause the min_delta event got missed,
> > so we need add a ETIME check here in case it happened.
> >
> > Cc: Daniel Lezcano <daniel.lezcano@...aro.org>
> > Cc: Arnd Bergmann <arnd@...db.de>
> > Cc: Thomas Gleixner <tglx@...utronix.de>
> > Cc: Shawn Guo <shawnguo@...nel.org>
> > Cc: Anson Huang <Anson.Huang@....com>
> > Cc: Bai Ping <ping.bai@....com>
> > Signed-off-by: Dong Aisheng <aisheng.dong@....com>
> >
> > ---
> > ChangeLog:
> > v3->v4:
> >  * also add ETIME explanation in function
> > v2->v3:
> >  * address all comments from Daniel Lezcano
> >  * add more explaination on ETIME check in commit message
> > v1->v2:
> >  * change to readl/writel from __raw_readl/writel according to Arnd's
> >    suggestion to avoid endian issue
> >  * add help information in Kconfig
> >  * add more error checking
> > ---
> >  drivers/clocksource/Kconfig         |   8 ++
> >  drivers/clocksource/Makefile        |   1 +
> >  drivers/clocksource/timer-imx-tpm.c | 239
> > ++++++++++++++++++++++++++++++++++++
> >  3 files changed, 248 insertions(+)
> >  create mode 100644 drivers/clocksource/timer-imx-tpm.c
> 
> [ ... ]
> 
> > +static struct irqaction tpm_timer_irq = {
> > +	.name		= "i.MX7ULP TPM Timer",
> > +	.flags		= IRQF_TIMER | IRQF_IRQPOLL,
> > +	.handler	= tpm_timer_interrupt,
> > +	.dev_id		= &clockevent_tpm,
> > +};
> >
> 
> Please remove the structure above and use request_irq instead of setup_irq
> below + return code checking.
> 

Okay, will switch to it.

> > +static int __init tpm_clockevent_init(unsigned long rate, int irq) {
> > +	setup_irq(irq, &tpm_timer_irq);
> > +
> > +	clockevent_tpm.cpumask = cpumask_of(0);
> > +	clockevent_tpm.irq = irq;
> > +	clockevents_config_and_register(&clockevent_tpm,
> > +					rate, 300, 0xfffffffe);
> > +
> > +	return 0;
> > +}
> > +
> > +static int __init tpm_timer_init(struct device_node *np) {
> 
> [ ... ]
> 
> > +	rate = clk_get_rate(per) >> 3;
> 
> Why ?
> 

Because TPM internally is configured to divide 8.

The full context is:
/* increase per cnt, div 8 by default */
writel(TPM_SC_CMOD_INC_PER_CNT | TPM_SC_CMOD_DIV_DEFAULT,
             timer_base + TPM_SC);

/* set MOD register to maximum for free running mode */
writel(0xffffffff, timer_base + TPM_MOD);

rate = clk_get_rate(per) >> 3;


> > +	tpm_clocksource_init(rate);
> > +	tpm_clockevent_init(rate, irq);
> 
> Check.
> 

Currently non of them return error code, do I still need to check?

> > +	return 0;
> > +
> > +err_per_clk_enable:
> > +	clk_disable_unprepare(ipg);
> > +err_ipg_clk_enable:
> 
> No need to add an extra label.
> 

Okay, will remove one.

> > +err_clk_get:
> > +	clk_put(per);
> > +	clk_put(ipg);
> > +err_iomap:
> > +	iounmap(timer_base);
> > +	return ret;
> > +}
> > +CLOCKSOURCE_OF_DECLARE(imx7ulp, "fsl,imx7ulp-tpm", tpm_timer_init);
> 
> CLOCKSOURCE_OF_DECLARE is renamed to TIMER_OF_DECLARE.
> 

Looks new, will change to it.

Thanks!

Regards
Dong Aisheng

> Thanks!
> 
>   -- Daniel
> 
> 
> --
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