linux-kernel - Re: [PATCH 3/7] rtc: pm8xxx: add support for uefi offset

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Message-ID: <Z45pEEofHiQRkR0D@hovoldconsulting.com>
Date: Mon, 20 Jan 2025 16:17:36 +0100
From: Johan Hovold <johan@...nel.org>
To: Sudeep Holla <sudeep.holla@....com>
Cc: Johan Hovold <johan+linaro@...nel.org>,
	Alexandre Belloni <alexandre.belloni@...tlin.com>,
	Bjorn Andersson <andersson@...nel.org>,
	Rob Herring <robh@...nel.org>,
	Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Conor Dooley <conor+dt@...nel.org>,
	Konrad Dybcio <konradybcio@...nel.org>,
	Jonathan Marek <jonathan@...ek.ca>, linux-arm-msm@...r.kernel.org,
	linux-rtc@...r.kernel.org, devicetree@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/7] rtc: pm8xxx: add support for uefi offset

On Mon, Jan 20, 2025 at 04:15:54PM +0100, Johan Hovold wrote:
> On Mon, Jan 20, 2025 at 03:10:24PM +0000, Sudeep Holla wrote:
> > On Mon, Jan 20, 2025 at 03:41:48PM +0100, Johan Hovold wrote:
> > > On many Qualcomm platforms the PMIC RTC control and time registers are
> > > read-only so that the RTC time can not be updated. Instead an offset
> > > needs be stored in some machine-specific non-volatile memory, which the
> > > driver can take into account.
> > > 
> > > Add support for storing a 32-bit offset from the GPS time epoch in a
> > > UEFI variable so that the RTC time can be set on such platforms.
> > >
> > 
> > Why can't the UEFI runtime services be used here ?
> > In short, why is drivers/rtc/rtc-efi.c not working or no attempts are
> > made to check if that works just fine ?
> 
> As I alluded to in the commit message, the Qualcomm UEFI implementation

s/commit message/cover letter/

> is broken and the runtime services cannot be accessed during runtime...
> 
> That's why we can't use rtc-efi and why we have a dedicated efivars
> implementation that talks directly to the firmware using a custom
> protocol:
> 
> 	https://lore.kernel.org/all/20220723224949.1089973-1-luzmaximilian@gmail.com/

Johan