linux-kernel - Re: [PATCH v2 0/4] Implement vendor resets for PSCI SYSTEM

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Date: Tue, 16 Apr 2024 10:35:22 +0100
From: Sudeep Holla <sudeep.holla@....com>
To: Elliot Berman <quic_eberman@...cinc.com>
Cc: Bjorn Andersson <andersson@...nel.org>,
	Konrad Dybcio <konrad.dybcio@...aro.org>,
	Sudeep Holla <sudeep.holla@....com>,
	Sebastian Reichel <sre@...nel.org>, Rob Herring <robh@...nel.org>,
	Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
	Conor Dooley <conor+dt@...nel.org>, Vinod Koul <vkoul@...nel.org>,
	Andy Yan <andy.yan@...k-chips.com>,
	Lorenzo Pieralisi <lpieralisi@...nel.org>,
	"Mark Rutland" <mark.rutland@....com>,
	Bartosz Golaszewski <bartosz.golaszewski@...aro.org>,
	Satya Durga Srinivasu Prabhala <quic_satyap@...cinc.com>,
	Melody Olvera <quic_molvera@...cinc.com>,
	Shivendra Pratap <quic_spratap@...cinc.com>,
	<devicetree@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	<linux-arm-kernel@...ts.infradead.org>,
	Florian Fainelli <florian.fainelli@...adcom.com>,
	<linux-pm@...r.kernel.org>, <linux-arm-msm@...r.kernel.org>
Subject: Re: [PATCH v2 0/4] Implement vendor resets for PSCI SYSTEM_RESET2

On Sun, Apr 14, 2024 at 12:30:23PM -0700, Elliot Berman wrote:
> The PSCI SYSTEM_RESET2 call allows vendor firmware to define additional
> reset types which could be mapped to the reboot argument.
>
> Setting up reboot on Qualcomm devices can be inconsistent from chipset
> to chipset.

That doesn't sound good. Do you mean PSCI SYSTEM_RESET doesn't work as
expected ? Does it mean it is not conformant to the specification ?

> Generally, there is a PMIC register that gets written to
> decide the reboot type. There is also sometimes a cookie that can be
> written to indicate that the bootloader should behave differently than a
> regular boot. These knobs evolve over product generations and require
> more drivers. Qualcomm firmwares are beginning to expose vendor
> SYSTEM_RESET2 types to simplify driver requirements from Linux.
>

Why can't this be fully userspace driven ? What is the need to keep the
cookie in the DT ?


-- 
Regards,
Sudeep