From: Samuel Holland <samuel@sholland.org>
To: Maxime Ripard <maxime@cerno.tech>
Cc: Alessandro Zummo <a.zummo@towertech.it>,
Alexandre Belloni <alexandre.belloni@bootlin.com>,
Chen-Yu Tsai <wens@csie.org>,
Jernej Skrabec <jernej.skrabec@siol.net>,
linux-rtc@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
linux-sunxi@lists.linux.dev, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] rtc: sun6i: Add NVMEM provider
Date: Sun, 9 May 2021 22:39:30 -0500 [thread overview]
Message-ID: <a3b03a06-c8fc-7dbe-7c0b-ffd1f194ecbc@sholland.org> (raw)
In-Reply-To: <20210430090206.lybmygrt636nysoc@gilmour>
On 4/30/21 4:02 AM, Maxime Ripard wrote:
> Hi,
>
> On Sun, Apr 18, 2021 at 08:45:49PM -0500, Samuel Holland wrote:
>> The sun6i RTC provides 32 bytes of general-purpose data registers.
>> They can be used to save data in the always-on RTC power domain.
>> The registers are writable via 32-bit MMIO accesses only.
>>
>> Expose the region as a NVMEM provider so it can be used by userspace and
>> other drivers.
>>
>> Signed-off-by: Samuel Holland <samuel@sholland.org>
>
> As far as I understood, you want to use those registers to implement
> super-standby? If so, while it makes sense for the kernel to be able to
> be able to write to those registers, I guess it would be a bit unwise to
> allow the userspace to access it?
I want the user to be able to pass information to the bootloader (to
select a boot device, e.g. reboot to FEL). I also want the user to be
able to read data stored to these registers by system firmware (e.g.
crust writes exception information there). It's not really related to
standby.
I would want to stack a nvmem-reboot-mode on top to give friendlier
names to some of the numbers, but I don't see a problem with root having
direct access to the registers. It's no different from /dev/nvram
providing access to the PC CMOS RAM.
Regards,
Samuel
next prev parent reply other threads:[~2021-05-10 3:39 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-04-19 1:45 [PATCH] rtc: sun6i: Add NVMEM provider Samuel Holland
2021-04-30 9:02 ` Maxime Ripard
2021-05-04 15:33 ` Alexandre Belloni
2021-05-10 3:39 ` Samuel Holland [this message]
2021-05-10 8:00 ` Alexandre Belloni
2021-05-25 8:24 ` Maxime Ripard
2021-05-27 4:09 ` Samuel Holland
2022-04-13 23:17 Samuel Holland
2022-04-15 18:26 ` Jernej Škrabec
2022-05-17 20:49 ` alexandre.belloni
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