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Message-ID: <b45b157593f1865a402f4098cdeafc298a294c6d.camel@linaro.org>
Date: Wed, 30 Jul 2025 09:44:48 +0100
From: André Draszik <andre.draszik@...aro.org>
To: Shivendra Pratap <shivendra.pratap@....qualcomm.com>, Bartosz
Golaszewski <bartosz.golaszewski@...aro.org>, Bjorn Andersson
<andersson@...nel.org>, Sebastian Reichel <sre@...nel.org>, Rob Herring
<robh@...nel.org>, Sudeep Holla <sudeep.holla@....com>, Souvik Chakravarty
<Souvik.Chakravarty@....com>, Krzysztof Kozlowski <krzk+dt@...nel.org>,
Conor Dooley <conor+dt@...nel.org>, Andy Yan <andy.yan@...k-chips.com>,
Mark Rutland <mark.rutland@....com>, Lorenzo Pieralisi
<lpieralisi@...nel.org>, Arnd Bergmann <arnd@...db.de>, Konrad Dybcio
<konradybcio@...nel.org>, cros-qcom-dts-watchers@...omium.org, Vinod Koul
<vkoul@...nel.org>, Catalin Marinas <catalin.marinas@....com>, Will Deacon
<will@...nel.org>, Florian Fainelli <florian.fainelli@...adcom.com>
Cc: Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>, Mukesh Ojha
<mukesh.ojha@....qualcomm.com>, Stephen Boyd <swboyd@...omium.org>,
linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org,
devicetree@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
linux-arm-msm@...r.kernel.org, Elliot Berman <quic_eberman@...cinc.com>,
Srinivas Kandagatla
<srini@...nel.org>
Subject: Re: [PATCH v13 07/10] firmware: psci: Implement vendor-specific
resets as reboot-mode
On Sun, 2025-07-27 at 21:54 +0530, Shivendra Pratap wrote:
> SoC vendors have different types of resets which are controlled
> through various hardware registers. For instance, Qualcomm SoC
> may have a requirement that reboot with “bootloader” command
> should reboot the device to bootloader flashing mode and reboot
> with “edl” should reboot the device into Emergency flashing mode.
> Setting up such reboots on Qualcomm devices can be inconsistent
> across SoC platforms and may require setting different HW
> registers, where some of these registers may not be accessible to
> HLOS. These knobs evolve over product generations and require
> more drivers. PSCI spec defines, SYSTEM_RESET2, vendor-specific
> reset which can help align this requirement. Add support for PSCI
> SYSTEM_RESET2, vendor-specific resets and align the implementation
> to allow user-space initiated reboots to trigger these resets.
>
> Introduce a late_initcall to register PSCI vendor-specific resets
> as reboot modes. Implement a reboot-mode write function that sets
> reset_type and cookie values during the reboot notifier callback.
> Introduce a firmware-based call for SYSTEM_RESET2 vendor-specific
> reset in the psci_sys_reset path, using reset_type and cookie if
> supported by secure firmware.
>
> By using the above implementation, userspace will be able to issue
> such resets using the reboot() system call with the "*arg"
> parameter as a string based command. The commands can be defined
> in PSCI device tree node as “reset-types” and are based on the
> reboot-mode based commands.
>
> Signed-off-by: Shivendra Pratap <shivendra.pratap@....qualcomm.com>
> ---
> drivers/firmware/psci/Kconfig | 2 ++
> drivers/firmware/psci/psci.c | 57 ++++++++++++++++++++++++++++++++++++++++++-
> 2 files changed, 58 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/firmware/psci/Kconfig b/drivers/firmware/psci/Kconfig
> index 97944168b5e66aea1e38a7eb2d4ced8348fce64b..93ff7b071a0c364a376699733e6bc5654d56a17f 100644
> --- a/drivers/firmware/psci/Kconfig
> +++ b/drivers/firmware/psci/Kconfig
> @@ -1,6 +1,8 @@
> # SPDX-License-Identifier: GPL-2.0-only
> config ARM_PSCI_FW
> bool
> + select POWER_RESET
> + select REBOOT_MODE
>
> config ARM_PSCI_CHECKER
> bool "ARM PSCI checker"
> diff --git a/drivers/firmware/psci/psci.c b/drivers/firmware/psci/psci.c
> index 38ca190d4a22d6e7e0f06420e8478a2b0ec2fe6f..e14bcdbec1750db8aa9297c8bcdb242f58cc420e 100644
> --- a/drivers/firmware/psci/psci.c
> +++ b/drivers/firmware/psci/psci.c
> @@ -17,6 +17,7 @@
> #include <linux/printk.h>
> #include <linux/psci.h>
> #include <linux/reboot.h>
> +#include <linux/reboot-mode.h>
> #include <linux/slab.h>
> #include <linux/suspend.h>
>
> @@ -51,6 +52,14 @@ static int resident_cpu = -1;
> struct psci_operations psci_ops;
> static enum arm_smccc_conduit psci_conduit = SMCCC_CONDUIT_NONE;
>
> +struct psci_vendor_sysreset2 {
> + u32 reset_type;
> + u32 cookie;
> + bool valid;
> +};
> +
> +static struct psci_vendor_sysreset2 vendor_reset;
> +
> bool psci_tos_resident_on(int cpu)
> {
> return cpu == resident_cpu;
> @@ -309,7 +318,10 @@ static int get_set_conduit_method(const struct device_node *np)
> static int psci_sys_reset(struct notifier_block *nb, unsigned long action,
> void *data)
> {
> - if ((reboot_mode == REBOOT_WARM || reboot_mode == REBOOT_SOFT) &&
> + if (vendor_reset.valid && psci_system_reset2_supported) {
> + invoke_psci_fn(PSCI_FN_NATIVE(1_1, SYSTEM_RESET2), vendor_reset.reset_type,
> + vendor_reset.cookie, 0);
> + } else if ((reboot_mode == REBOOT_WARM || reboot_mode == REBOOT_SOFT) &&
> psci_system_reset2_supported) {
> /*
> * reset_type[31] = 0 (architectural)
I don't know the PSCI spec, but it looks like with this code it's not
possible to set a reboot mode (in DT) and at the same time instruct
the firmware whether a warm or a cold reboot was requested.
Doing warm reboot is useful if e.g. RAM contents needs to be retained
for crash recovery handling, or other reasons, while in normal cases
doing a more secure cold reboot.
On the other hand, of course it's useful to be able to specify the
reboot target for normal reboots.
Is this a problem with the PSCI spec or with this specific change
geared at the Qcom implementation?
> @@ -547,6 +559,49 @@ static const struct platform_suspend_ops psci_suspend_ops = {
> .enter = psci_system_suspend_enter,
> };
>
> +static int psci_set_vendor_sys_reset2(struct reboot_mode_driver *reboot, u64 magic)
> +{
> + u32 magic_32;
> +
> + if (psci_system_reset2_supported) {
> + magic_32 = magic & 0xFFFFFFFF;
I believe usual kernel style is to use lower case for
hex values.
> + vendor_reset.reset_type = PSCI_1_1_RESET_TYPE_VENDOR_START | magic_32;
> + vendor_reset.cookie = (magic >> 32) & 0xFFFFFFFF;
dito.
Cheers,
Andre'
> + vendor_reset.valid = true;
> + }
> +
> + return NOTIFY_DONE;
> +}
> +
> +static int __init psci_init_vendor_reset(void)
> +{
> + struct reboot_mode_driver *reboot;
> + struct device_node *np;
> + int ret;
> +
> + np = of_find_node_by_path("/psci/reboot-mode");
> + if (!np)
> + return -ENODEV;
> +
> + reboot = kzalloc(sizeof(*reboot), GFP_KERNEL);
> + if (!reboot) {
> + of_node_put(np);
> + return -ENOMEM;
> + }
> +
> + reboot->write = psci_set_vendor_sys_reset2;
> +
> + ret = reboot_mode_register(reboot, np, "psci");
> + if (ret) {
> + of_node_put(np);
> + kfree(reboot);
> + return ret;
> + }
> +
> + return 0;
> +}
> +late_initcall(psci_init_vendor_reset)
> +
> static void __init psci_init_system_reset2(void)
> {
> int ret;
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