Re: [PATCH v2 0/4] Implement vendor resets for PSCI SYSTEM_RESET2

From: Sudeep Holla <sudeep.holla@arm.com>
To: Elliot Berman <quic_eberman@quicinc.com>
Cc: Bjorn Andersson <andersson@kernel.org>,
	Konrad Dybcio <konrad.dybcio@linaro.org>,
	Sudeep Holla <sudeep.holla@arm.com>,
	Sebastian Reichel <sre@kernel.org>, Rob Herring <robh@kernel.org>,
	Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>,
	Conor Dooley <conor+dt@kernel.org>, Vinod Koul <vkoul@kernel.org>,
	Andy Yan <andy.yan@rock-chips.com>,
	Lorenzo Pieralisi <lpieralisi@kernel.org>,
	"Mark Rutland" <mark.rutland@arm.com>,
	Bartosz Golaszewski <bartosz.golaszewski@linaro.org>,
	Satya Durga Srinivasu Prabhala <quic_satyap@quicinc.com>,
	Melody Olvera <quic_molvera@quicinc.com>,
	Shivendra Pratap <quic_spratap@quicinc.com>,
	<devicetree@vger.kernel.org>, <linux-kernel@vger.kernel.org>,
	<linux-arm-kernel@lists.infradead.org>,
	Florian Fainelli <florian.fainelli@broadcom.com>,
	<linux-pm@vger.kernel.org>, <linux-arm-msm@vger.kernel.org>
Subject: Re: [PATCH v2 0/4] Implement vendor resets for PSCI SYSTEM_RESET2
Date: Tue, 16 Apr 2024 10:35:22 +0100	[thread overview]
Message-ID: <Zh5GWqt2oCNHdF_h@bogus> (raw)
In-Reply-To: <20240414-arm-psci-system_reset2-vendor-reboots-v2-0-da9a055a648f@quicinc.com>

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