linux-kernel - Re: [PATCH v3 2/2] clocksource/drivers/timer-microchip-pit64b: add Microchip PIT64B support

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Message-ID: <d104a0d3-950d-3132-4bf8-d06ccb7c6f25@linaro.org>
Date:   Tue, 10 Dec 2019 12:51:08 +0100
From:   Daniel Lezcano <daniel.lezcano@...aro.org>
To:     Claudiu.Beznea@...rochip.com, robh+dt@...nel.org,
        mark.rutland@....com, Nicolas.Ferre@...rochip.com,
        alexandre.belloni@...tlin.com, Ludovic.Desroches@...rochip.com,
        tglx@...utronix.de
Cc:     devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v3 2/2] clocksource/drivers/timer-microchip-pit64b: add
 Microchip PIT64B support

On 10/12/2019 12:43, Claudiu.Beznea@...rochip.com wrote:
> 
> 
> On 09.12.2019 19:04, Daniel Lezcano wrote:
>> On 04/12/2019 15:42, Claudiu Beznea wrote:
>>> Add driver for Microchip PIT64B timer. Timer could be used in continuous
>>> mode or oneshot mode. The hardware has 2x32 bit registers for period
>>> emulating a 64 bit timer. The LSB_PR and MSB_PR registers are used to
>>> set the period value (compare value). TLSB and TMSB keeps the current
>>> value of the counter. After a compare the TLSB and TMSB register resets.
>>> The driver uses PIT64B timer for clocksource or clockevent. First
>>> requested timer would be registered as clockevent, second one would be
>>> registered as clocksource. Individual PIT64B hardware resources were used
>>> for clocksource and clockevent to be able to support high resolution
>>> timers with this hardware implementation.
>>>
>>> Signed-off-by: Claudiu Beznea <claudiu.beznea@...rochip.com>
>>> ---

[ ... ]

>> Also, the 'high' part change may be checked, like:
>>
>> https://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm.git/tree/drivers/clocksource/timer-imx-sysctr.c?h=bleeding-edge#n51
> 
> The IP guarantees that the reading of counter is atomic if
> MCHP_PIT64B_TLSBR is read first. With this, would you still want to add the
> check you mention above?

No, sorry I should have read the comment :/

[ ... ]


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