From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 8D86B2F6569; Tue, 18 Nov 2025 12:28:27 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1763468907; cv=none; b=CRCDuSoPBK3K0Q9L4f0tGp6UchkxjH+UAYKTZ2RVPmc9/2Yvq75K6nTiTO7H1um5wVLp866yX2YNkfac8jZsjCNA6tUHpo+wSzSETGk68O90UX+PHmMAVzSH4qDjAQ5dpg3GzOe9AK6L2yfB0NJi/jy0xLeUYZhZHzdOudBcyBg= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1763468907; c=relaxed/simple; bh=HkElddSNiWQx84TT3HUUBpi/rNgO0A/CKPAtgfrEFa8=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=ISLPbjpA9k0RKAGmYIKv4/DWWF6By5rtd7haKEVxTvwexs3CqxRFAMlPW5uPoggqFzx0/B4fRpo8Wclznd7sCgJLBhper5sZbkGFAu+W6FEjy4mftG6/xUfgEl17IsnRC9tOorNOFTvF2T6atFVq7Hz69wxgoIIVrT5Yh2u0f6Y= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=X0zU4oM1; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="X0zU4oM1" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 33852C4CEFB; Tue, 18 Nov 2025 12:28:13 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1763468905; bh=HkElddSNiWQx84TT3HUUBpi/rNgO0A/CKPAtgfrEFa8=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=X0zU4oM1pH8YX2XK6W2GczfPtfKY6olP8Z/ZMzR7Jg8Aa+8BSORrRNvrMFXHb80q+ UnxHc6Ywp1OIXy+rIqum7VGZ7Aaj+ryNouvyEJlNDltxDdF4f3R5SIuToTZ24zY1+f spPVFf2ylUfTQs2A/EQLfWO6+mWwfqRkY7NH02wbMlNi9FQsRj6F5kkoXIAWWcMd2K rTow1dvi13KG7jMvA+FgBWq/bbxS/oLHwkP3pm6C0PBRjPebfw5jOYytDHgF7BdqfW y3wS8UoI0Q+MoWethNO00zDIuamTBJAmpVRnqQCwxQ80JKQVllJ5vpU3uyolQez6Wb 4ZDPOU5gXd0Gg== Date: Tue, 18 Nov 2025 13:28:10 +0100 From: Lorenzo Pieralisi To: Shivendra Pratap Cc: Bartosz Golaszewski , Bjorn Andersson , Sebastian Reichel , Rob Herring , Sudeep Holla , Souvik Chakravarty , Krzysztof Kozlowski , Conor Dooley , Andy Yan , Mark Rutland , Arnd Bergmann , Konrad Dybcio , cros-qcom-dts-watchers@chromium.org, Vinod Koul , Catalin Marinas , Will Deacon , Florian Fainelli , Moritz Fischer , John Stultz , Matthias Brugger , Krzysztof Kozlowski , Dmitry Baryshkov , Mukesh Ojha , Stephen Boyd , Andre Draszik , Kathiravan Thirumoorthy , linux-pm@vger.kernel.org, linux-kernel@vger.kernel.org, devicetree@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-arm-msm@vger.kernel.org, Elliot Berman , Xin Liu , Srinivas Kandagatla , Umang Chheda , Nirmesh Kumar Singh Subject: Re: [PATCH v17 07/12] firmware: psci: Implement vendor-specific resets as reboot-mode Message-ID: References: <20251109-arm-psci-system_reset2-vendor-reboots-v17-0-46e085bca4cc@oss.qualcomm.com> <20251109-arm-psci-system_reset2-vendor-reboots-v17-7-46e085bca4cc@oss.qualcomm.com> <80e68e44-a8e0-464a-056e-9f087ad40d51@oss.qualcomm.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <80e68e44-a8e0-464a-056e-9f087ad40d51@oss.qualcomm.com> On Mon, Nov 17, 2025 at 11:14:48PM +0530, Shivendra Pratap wrote: > > > On 11/10/2025 10:52 PM, Lorenzo Pieralisi wrote: > > On Sun, Nov 09, 2025 at 08:07:20PM +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. > >> > >> Implement the PSCI vendor-specific resets by registering to the > >> reboot-mode framework. > > > > I think that we should expose to user space _all_ PSCI reset types, > > cold, warm + vendor specific - as a departure from using the reboot_mode > > variable (and possibly deprecate it - or at least stop using it). > > sure. We can try that. Have tried to compile it all at the end of this thread. > > > > >> As psci init is done at early kernel init, reboot-mode registration cannot > >> be done at the time of psci init. This is because reboot-mode creates a > >> “reboot-mode” class for exposing sysfs, which can fail at early kernel init. > >> To overcome this, 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. Register a panic notifier and clear vendor_reset valid status > >> during panic. This is needed for any kernel panic that occurs post > >> reboot_notifiers. > > > > Is it because panic uses reboot_mode to determine the reset to issue ? > > Yes. As we know, currently psci supports only two resets, > psci_sys_reset2 (ARCH warm reset) and psci_sys_reset(COLD RESET). And kernel > panic path should take the path set by reboot_mode to maintain backward > compatibility. > > > > >> 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 under “reboot-mode” and are based on the > >> reboot-mode based commands. > > > > IMHO - it would be nice if could add mode-cold (or mode-normal in reboot mode > > speak) and mode-warm by default (if PSCI supports them) so that userspace > > Default mode in current kernel is cold, until explicitly set to warm. > So should it be defaulted to cold? I managed to confuse you sorry. What I wanted to say is that user space should be able to issue _all_ PSCI resets (inclusive of cold and warm if supported - ie if SYSTEM_RESET2 is supported) not just vendor resets. I misused "by default" - I meant cold and warm PSCI resets should be part of the reboot-mode list. [...] > >> > >> +struct psci_vendor_sysreset2 { > >> + u32 reset_type; > >> + u32 cookie; > >> + bool valid; > >> +}; > >> + > >> +static struct psci_vendor_sysreset2 vendor_reset; > > > > I think this should represent all possible PSCI reset types, not vendor only > > and its value is set by the reboot mode framework. > > > >> + > >> +static int psci_panic_event(struct notifier_block *nb, unsigned long v, void *p) > >> +{ > >> + vendor_reset.valid = false; > > > > I don't like this. Basically all you want this for is to make sure that > > we don't override the reboot_mode variable. > > Yes, it does not look good but as we planned to use reboot-mode framework earlier, which > sets the modes at the at reboot_notifiers. This needs to be taken care for any panic > that occurs between reboot_notifier and restart_notifier. Isn't there a simpler way to detect whether we are in panic mode and consequently we just issue a reset based on reboot_mode ? panic_in_progress() ? > > One (hack) would consist in checking the reboot_mode variable here and > > set the struct I mentioned above to the value represented in reboot_mode. > > > > Good luck if reboot_mode == REBOOT_GPIO :-) > > psci supports only two modes, ARCH_WARM and cold, so anything else except WARM/SOFT > should default to cold? So even if REBOOT_GPIO is set in reboot_mode, we should default > it to cold reset. > > > > >> + return NOTIFY_DONE; > >> +} > >> + > >> +static struct notifier_block psci_panic_block = { > >> + .notifier_call = psci_panic_event > >> +}; > >> + > >> bool psci_tos_resident_on(int cpu) > >> { > >> return cpu == resident_cpu; > >> @@ -309,7 +330,10 @@ 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); > > > > See above. Two calls here: one for resets issued using the new userspace > > interface you are adding and legacy below - no vendor vs reboot_mode, this > > is a mess. > > Are we suggesting to completely remove the reboot_mode check from here in the new > design and base it on reboot param? I am suggesting that there must be two reset options: - based on reboot mode set by user space - based on reboot_mode variable (as a fallback and while panic is in progress) > > > >> + } else if ((reboot_mode == REBOOT_WARM || reboot_mode == REBOOT_SOFT) && > >> psci_system_reset2_supported) { > >> /* > >> * reset_type[31] = 0 (architectural) > >> @@ -547,6 +571,72 @@ 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 & GENMASK(31, 0); > >> + vendor_reset.reset_type = PSCI_1_1_RESET_TYPE_VENDOR_START | magic_32; > >> + vendor_reset.cookie = (magic >> 32) & GENMASK(31, 0); > > > > Use FIELD_PREP/GET() please (but as mentioned above the vendor reset type > > bit[31] should be part of the reboot mode magic value, see above). > > sure. Will align this. thanks. > > > > >> + vendor_reset.valid = true; > >> + } > >> + > >> + return NOTIFY_DONE; > >> +} > >> + > >> +static int __init psci_init_vendor_reset(void) > >> +{ > >> + struct reboot_mode_driver *reboot; > >> + struct device_node *psci_np; > >> + struct device_node *np; > >> + int ret; > >> + > >> + if (!psci_system_reset2_supported) > >> + return -EINVAL; > >> + > >> + psci_np = of_find_compatible_node(NULL, NULL, "arm,psci-1.0"); > >> + if (!psci_np) > >> + return -ENODEV; > >> + > >> + np = of_find_node_by_name(psci_np, "reboot-mode"); > >> + if (!np) { > >> + of_node_put(psci_np); > >> + return -ENODEV; > >> + } > >> + > >> + ret = atomic_notifier_chain_register(&panic_notifier_list, &psci_panic_block); > >> + if (ret) > >> + goto err_notifier; > >> + > >> + reboot = kzalloc(sizeof(*reboot), GFP_KERNEL); > >> + if (!reboot) { > >> + ret = -ENOMEM; > >> + goto err_kzalloc; > >> + } > >> + > >> + reboot->write = psci_set_vendor_sys_reset2; > >> + reboot->driver_name = "psci"; > >> + > >> + ret = reboot_mode_register(reboot, of_fwnode_handle(np)); > >> + if (ret) > >> + goto err_register; > >> + > >> + of_node_put(psci_np); > >> + of_node_put(np); > >> + return 0; > >> + > >> +err_register: > >> + kfree(reboot); > >> +err_kzalloc: > >> + atomic_notifier_chain_unregister(&panic_notifier_list, &psci_panic_block); > >> +err_notifier: > >> + of_node_put(psci_np); > >> + of_node_put(np); > >> + return ret; > >> +} > >> +late_initcall(psci_init_vendor_reset) > > > > I don't like adding another initcall here. > > > > I wonder whether this code belongs in a PSCI reboot mode driver, possibly a > > faux device in a way similar to what we did for cpuidle-psci (that after all > > is a consumer of PSCI_CPU_SUSPEND in a similar way as this code is a > > PSCI_SYSTEM_RESET{2} consumer), that communicates with > > drivers/firmware/psci/psci.c with the struct mentioned above. > > sure. we can create a new driver and try it as in cpuidle: cpuidle-psci. > Can you suggest a bit more on the overall approach we want to take here? > Have tried to summarize the potential changes and few questions below. > > - new driver registers a faux device - say - power: reset: psci_reset. Yes this could be a potential way forward but that's decoupled from the options below. If we take this route PSCI maintainers should be added as maintainers for this reboot mode driver. > - struct with pre-built psci reset_types - (warm, soft, cold). Currently > only two modes supported, anything other than warm/soft defaults to cold. > - vendor resets to be added as per vendor choice, inside psci device tree(SOC specific). > - psci_reset registers with reboot-mode for registering vendor resets. Here, we > have a problem, the pre-built psci reset_types - (warm, soft, cold) cannot be added via > reboot-mode framework. Why ? > Should the new psci_reset driver, move away from reboot-mode > framework as-well? And define its own parsing logic for psci_reset_types, > and have its own restart_notifier instead of reboot_notifier? No. As I said earlier, I think it makes sense to allow user space to select _all_ PSCI reset types - architected and vendor specific in a single reboot mode driver. I believe that we must be able to have two well defined ways for issuing resets: - one based on reboot mode driver - one based on reboot_mode variable interface Does this make sense everyone ? I don't know the history behind reboot_mode and the reboot mode driver framework I am just stating what I think makes sense to do for PSCI. Thanks, Lorenzo > - If new psci_reset driver move away from reboot-mode, we can get rid of the panic_notifier > added in the psci code. Else, we may still need the panic_notifier for any kernel panic > that occurs between reboot_notifier and restart_notifier? > - psci driver will export a function which will be called externally to set the current > psci reset_type. > - psci_sys_reset in psci driver should remove the check on reboot_mode. It will default to > cold reset (for the reason the current kernel defaults to cold reset in psci.) > example change in psci_sys_reset: > if(psci_system_reset2_supported && != cold) > psci_sys_reset2(AS PER PARAMS FROM new psci_reset driver) > else > psci_sys_reset(COLD RESET) > > thanks, > Shivendra