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Date:   Wed, 15 Jan 2020 14:54:57 -0300
From:   Paul Cercueil <paul@crapouillou.net>
Subject: Re: [PATCH v3] clocksource: Add driver for the Ingenic JZ47xx OST
To:     Maarten ter Huurne <maarten@treewalker.org>
Cc:     Daniel Lezcano <daniel.lezcano@linaro.org>,
        Thomas Gleixner <tglx@linutronix.de>, od@zcrc.me,
        linux-kernel@vger.kernel.org, Mathieu Malaterre <malat@debian.org>,
        Artur Rojek <contact@artur-rojek.eu>
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Le mer., janv. 15, 2020 at 18:48, Maarten ter Huurne=20
<maarten@treewalker.org> a =E9crit :
> On Wednesday, 15 January 2020 14:57:01 CET Paul Cercueil wrote:
>>  Le mer., janv. 15, 2020 at 14:44, Daniel Lezcano
>>  <daniel.lezcano@linaro.org> a =E9crit :
>>  > Is the JZ47xx OST really a mfd needing a regmap? (Note regmap_read
>>  > will take a lock).
>>=20
>>  Yes, the TCU_REG_OST_TCSR register is shared with the clocks driver.
>=20
> The TCU_REG_OST_TCSR register is only used in the probe though.
>=20
> To get the counter value from TCU_REG_OST_CNTL/TCU_REG_OST_CNTH you
> could technically do it by reading the register directly, if=20
> performance
> concerns make it necessary to bypass the usual kernel infrastructure=20
> for
> dealing with shared registers.

In theory yes, in practice there's no easy way to do that (the=20
underlying mmio pointer is not obtainable from the regmap), and=20
besides, the lock is just a spinlock and not a mutex.

-Paul

=