From: Boris Brezillon <boris.brezillon@free-electrons.com>
To: Daniel Lezcano <daniel.lezcano@linaro.org>
Cc: Alexandre Belloni <alexandre.belloni@free-electrons.com>,
Thomas Gleixner <tglx@linutronix.de>,
Nicolas Ferre <nicolas.ferre@atmel.com>,
Jean-Christophe Plagniol-Villard <plagnioj@jcrosoft.com>,
linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH 42/48] clocksource/drivers: Add a new driver for the Atmel ARM TC blocks
Date: Wed, 22 Jun 2016 15:13:29 +0200 [thread overview]
Message-ID: <20160622151329.4f0136ba@bbrezillon> (raw)
In-Reply-To: <576A8D74.5000804@linaro.org>
On Wed, 22 Jun 2016 15:07:00 +0200
Daniel Lezcano <daniel.lezcano@linaro.org> wrote:
> On 06/11/2016 02:48 PM, Boris Brezillon wrote:
>
> [ ... ]
>
> >> +static int tcb_clkevt_next_event(unsigned long delta,
> >> + struct clock_event_device *d)
> >> +{
> >> + u32 val;
> >> +
> >> + regmap_read(tc.regmap, ATMEL_TC_CV(tc.channels[0]), &val);
> >> + regmap_write(tc.regmap, ATMEL_TC_RC(tc.channels[0]), val + delta);
> >> + regmap_write(tc.regmap, ATMEL_TC_IER(tc.channels[0]), ATMEL_TC_CPCS);
> >
> > Hm, not sure this is 100% sure. What happens if by the time you write
> > TC_RC, the delta value has expired? This means you'll have to wait
> > another round before the TC engine generates the "RC reached" interrupt.
> >
> > I know this is very unlikely, but should we take the risk?
> >
> > The core seems to check the ->set_next_event() return value and tries to
> > adjust ->min_delta_ns if it returns an error, so maybe it's worth
> > testing if val + delta has already occurred just before enabling the
> > TC_CPCS interrupt, and if it's the case, return an -ETIME error.
> >
> > Something like:
> >
> > u32 val[2], next;
> >
> > regmap_read(tc.regmap, ATMEL_TC_CV(tc.channels[0]), &val[0]);
> > next = (val[0] + delta) & GENMASK(tc.bits - 1, 0);
> > regmap_write(tc.regmap, ATMEL_TC_RC(tc.channels[0]), next);
> > regmap_read(tc.regmap, ATMEL_TC_CV(tc.channels[0]), &val[1]);
> >
> > if ((next < val[0] && val[1] < val[0] && val[1] >= next) ||
> > (next > val[0] && (val[1] < val[0] || val[1] >= next))) {
> > /*
> > * Clear the CPCS bit in the status register to avoid
> > * generating a spurious interrupt next time a valid
> > * timer event is configured.
> > * FIXME: not sure it's safe, since it also clears the
> > * overflow status, but it seems this flag is not used
> > * by the driver anyway.
> > */
> > regmap_read(tc.regmap, ATMEL_TC_SR, &val[0]);
> > return -ETIME;
> > }
> >
> >
> > regmap_write(tc.regmap, ATMEL_TC_IER(tc.channels[0]),
> > ATMEL_TC_CPCS);
> >
> > Thomas, Daniel, what's your opinion?
>
> Are you describing the same as commit
> f9eccf24615672896dc13251410c3f2f33a14f95 ?
Pretty much, yes. Note that this is purely hypothetical in the TCB
case, but I fear people might experience this problem if they're trying
to configure tiny delay values.
next prev parent reply other threads:[~2016-06-22 13:24 UTC|newest]
Thread overview: 75+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-06-10 22:03 [PATCH 00/48] ARM: at91: rework Atmel TCB drivers Alexandre Belloni
2016-06-10 22:03 ` [PATCH 01/48] clk: at91: replace usleep() by udelay() calls Alexandre Belloni
2016-06-10 22:30 ` Arnd Bergmann
2016-06-10 22:37 ` Alexandre Belloni
2016-06-13 15:24 ` Alexandre Belloni
2016-06-13 19:26 ` Arnd Bergmann
2016-06-14 16:05 ` Afzal Mohammed
2016-06-14 16:18 ` Boris Brezillon
2016-06-11 7:49 ` Boris Brezillon
2016-06-10 22:03 ` [PATCH 02/48] ARM: at91: Document new TCB bindings Alexandre Belloni
2016-06-14 21:47 ` Rob Herring
2016-06-15 7:29 ` Boris Brezillon
2016-06-21 20:08 ` Rob Herring
2016-06-21 20:28 ` Rob Herring
2016-06-10 22:03 ` [PATCH 03/48] ARM: dts: at91: at91rm9200: TC blocks are also simple-mfd and syscon devices Alexandre Belloni
2016-06-10 22:03 ` [PATCH 04/48] ARM: dts: at91: at91rm9200ek; use TCB0 as clocksource Alexandre Belloni
2016-06-10 22:03 ` [PATCH 05/48] ARM: dts: at91: mpa1600; " Alexandre Belloni
2016-06-10 22:03 ` [PATCH 06/48] ARM: dts: at91: at91sam9260: TC blocks are also simple-mfd and syscon devices Alexandre Belloni
2016-06-10 22:03 ` [PATCH 07/48] ARM: dts: at91: ethernut5: use TCB0 as clocksource Alexandre Belloni
2016-06-10 22:03 ` [PATCH 08/48] ARM: dts: at91: foxg20: " Alexandre Belloni
2016-06-10 22:03 ` [PATCH 09/48] ARM: dts: at91: animeo_ip: " Alexandre Belloni
2016-06-10 22:03 ` [PATCH 10/48] ARM: dts: at91: kizbox: " Alexandre Belloni
2016-06-10 22:03 ` [PATCH 11/48] ARM: dts: at91: at91sam9g20ek: " Alexandre Belloni
2016-06-10 22:03 ` [PATCH 12/48] ARM: dts: at91: ge863-pro3: " Alexandre Belloni
2016-06-10 22:03 ` [PATCH 13/48] ARM: dts: at91: at91sam9261: TC blocks are also simple-mfd and syscon devices Alexandre Belloni
2016-06-10 22:03 ` [PATCH 14/48] ARM: dts: at91: at91sam9261ek: use TCB0 as clocksource Alexandre Belloni
2016-06-10 22:03 ` [PATCH 15/48] ARM: dts: at91: at91sam9263: TC blocks are also simple-mfd and syscon devices Alexandre Belloni
2016-06-10 22:03 ` [PATCH 16/48] ARM: dts: at91: at91sam9263ek: use TCB0 as clocksource Alexandre Belloni
2016-06-10 22:03 ` [PATCH 17/48] ARM: dts: at91: calao: " Alexandre Belloni
2016-06-10 22:03 ` [PATCH 18/48] ARM: dts: at91: at91sam9g45: TC blocks are also simple-mfd and syscon devices Alexandre Belloni
2016-06-10 22:03 ` [PATCH 19/48] ARM: dts: at91: at91sam9m10g45ek: use TCB0 as clocksource Alexandre Belloni
2016-06-10 22:03 ` [PATCH 20/48] ARM: dts: at91: pm9g45: " Alexandre Belloni
2016-06-10 22:03 ` [PATCH 21/48] ARM: dts: at91: at91sam9rl: TC blocks are also simple-mfd and syscon devices Alexandre Belloni
2016-06-10 22:03 ` [PATCH 22/48] ARM: dts: at91: at91sam9rlek: use TCB0 as clocksource Alexandre Belloni
2016-06-10 22:03 ` [PATCH 23/48] ARM: dts: at91: at91sam9n12: TC blocks are also simple-mfd and syscon devices Alexandre Belloni
2016-06-10 22:03 ` [PATCH 24/48] ARM: dts: at91: at91sam9n12ek: use TCB0 as clocksource Alexandre Belloni
2016-06-10 22:03 ` [PATCH 25/48] ARM: dts: at91: at91sam9x5: TC blocks are also simple-mfd and syscon devices Alexandre Belloni
2016-06-10 22:03 ` [PATCH 26/48] ARM: dts: at91: at91sam9x5cm: use TCB0 as clocksource Alexandre Belloni
2016-06-10 22:03 ` [PATCH 27/48] ARM: dts: at91: acme/g25: " Alexandre Belloni
2016-06-10 22:03 ` [PATCH 28/48] ARM: dts: at91: cosino: " Alexandre Belloni
2016-06-10 22:03 ` [PATCH 29/48] ARM: dts: at91: kizboxmini: " Alexandre Belloni
2016-06-10 22:03 ` [PATCH 30/48] ARM: dts: at91: sama5d3: TC blocks are also simple-mfd and syscon devices Alexandre Belloni
2016-06-10 22:03 ` [PATCH 31/48] ARM: dts: at91: sama5d3xek; use TCB0 as clocksource Alexandre Belloni
2016-06-10 22:03 ` [PATCH 32/48] ARM: dts: at91: sama5d3 Xplained: " Alexandre Belloni
2016-06-10 22:03 ` [PATCH 33/48] ARM: dts: at91: kizbox2: " Alexandre Belloni
2016-06-10 22:03 ` [PATCH 34/48] ARM: dts: at91: sama5d4: TC blocks are also simple-mfd and syscon devices Alexandre Belloni
2016-06-10 22:03 ` [PATCH 35/48] ARM: dts: at91: sama5d4: Add TCB2 Alexandre Belloni
2016-06-10 22:03 ` [PATCH 36/48] ARM: dts: at91: sama5d4ek: use TCB2 as clocksource Alexandre Belloni
2016-06-10 22:03 ` [PATCH 37/48] ARM: dts: at91: sama5d4 Xplained: " Alexandre Belloni
2016-06-10 22:03 ` [PATCH 38/48] ARM: dts: at91: ma5d4: " Alexandre Belloni
2016-06-10 22:03 ` [PATCH 39/48] ARM: dts: at91: vinco: " Alexandre Belloni
2016-06-10 22:03 ` [PATCH 40/48] ARM: dts: at91: sama5d2: TC blocks are also simple-mfd and syscon devices Alexandre Belloni
2016-06-10 22:03 ` [PATCH 41/48] ARM: dts: at91: sama5d2 Xplained: use TCB0 as clocksource Alexandre Belloni
2016-06-10 22:03 ` [PATCH 42/48] clocksource/drivers: Add a new driver for the Atmel ARM TC blocks Alexandre Belloni
2016-06-11 12:48 ` Boris Brezillon
2016-06-22 13:07 ` Daniel Lezcano
2016-06-22 13:13 ` Boris Brezillon [this message]
2016-06-24 10:07 ` Daniel Lezcano
2017-05-16 11:59 ` Alexandre Belloni
2017-05-16 14:25 ` Daniel Lezcano
2017-05-16 14:35 ` Alexandre Belloni
2016-06-10 22:03 ` [PATCH 43/48] clocksource/drivers: Add a clockevent driver for Atmel " Alexandre Belloni
2016-06-10 22:03 ` [PATCH 44/48] clocksource: atmel-pit: allow unselecting ATMEL_PIT Alexandre Belloni
2016-06-11 9:43 ` Thomas Gleixner
2016-06-11 10:53 ` Alexandre Belloni
2016-06-13 19:04 ` Boris Brezillon
2016-06-13 19:14 ` Thomas Gleixner
2016-06-16 14:41 ` Boris Brezillon
2016-06-10 22:03 ` [PATCH 45/48] ARM: at91/defconfig: sama5: unselect ATMEL_PIT Alexandre Belloni
2016-06-10 22:03 ` [PATCH 46/48] ARM: at91/defconfig: at91_dt " Alexandre Belloni
2016-06-10 22:03 ` [PATCH 47/48] PWM: atmel-tcb: switch to new binding Alexandre Belloni
2016-06-11 2:22 ` kbuild test robot
2016-06-10 22:03 ` [PATCH 48/48] ARM: dts: at91: kizbox: switch to new pwm-atmel-tcb binding Alexandre Belloni
2016-06-11 0:14 ` kbuild test robot
2016-06-11 10:25 ` Alexandre Belloni
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