From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 18194C369C2 for ; Wed, 16 Apr 2025 12:23:40 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:In-Reply-To:Content-Type: MIME-Version:References:Message-ID:Subject:Cc:To:From:Date:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=ZvN8SOjmNm8vvVPr99tsFG2WGFqFOuiF5wi0Uvwa5Ow=; b=qSLmvGwUGCA4ToxWMO5b3Tg2aV 7tyYE9qIbA2kkRPDpPAB9e6Xhx2dLap0LJV/QaYbRIldDp3bs1ybNPnI27sWqKen0mdkVVcLGhAT+ yRzqxvtUyU5u0v3x/GHi53jBRazBk1PMjAPU7zCEJHrf0C5rRakpwFCOA0SOsdM/SGB9R2sSz6ZDj TNKZppJHETp43WZS0vSns34KRTcMHiZjJ9I8bWwVaxDPIdurkB1u/CHspIm0QpfulD0fJkQWxS0tU cXvGv8M0w9VCkWezPz2Pe1nbXqrUyXtGeQ6RcB3OVYxTWmlHUgAuznCiu5XJ8qtEBk9fRAVeOF2FG MfZVhyzQ==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98.2 #2 (Red Hat Linux)) id 1u51nf-00000009Uop-0GZk; Wed, 16 Apr 2025 12:23:31 +0000 Received: from nyc.source.kernel.org ([147.75.193.91]) by bombadil.infradead.org with esmtps (Exim 4.98.2 #2 (Red Hat Linux)) id 1u51Wf-00000009RIf-0gxe for linux-arm-kernel@lists.infradead.org; Wed, 16 Apr 2025 12:05:58 +0000 Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by nyc.source.kernel.org (Postfix) with ESMTP id 7B9A2A43191; Wed, 16 Apr 2025 12:00:27 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id D45FAC4CEE2; Wed, 16 Apr 2025 12:05:46 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1744805155; bh=bnMHt1rL/O6Hg4QOcjQu/TboqXC7jvmxdMfDriXSJrI=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=pafbQmE0kdKd2epxSFbX+aHj66P+4Irm/VJM0YBN2/Us1PDyFps2Hwx05AkWO0eIb T/LJTHBvb2Ixpd9fE4uspC+NmUYvjrZ+PB47zKk/Y7DyJuNqjGPouPQYbPwVAAvoEl 89wXmy7bm/3ey0J/fgTpt9X7iJJMSn8V21uVhlm8HuoAlUyKU3ZdqIyLPyO8312AYb CJQgk9FNYOWRLqK/ClgrcpjSnGg/gHRLtRrcR7O3kN1q8PpZibBq+7TlgZjHNxXt6u BbQv9wBaEhz5nM85jvH/tVhCF7wkp8oCkuE39Nx0LAyyTPsOFgBGD0wuy2+b+kXBnv VSus8NV6ceJpw== Date: Wed, 16 Apr 2025 14:05:44 +0200 From: Lorenzo Pieralisi To: Shivendra Pratap Cc: Mukesh Ojha , Elliot Berman , Bjorn Andersson , Sebastian Reichel , Rob Herring , Conor Dooley , Vinod Koul , Andy Yan , Mark Rutland , Bartosz Golaszewski , Arnd Bergmann , Olof Johansson , Catalin Marinas , Will Deacon , cros-qcom-dts-watchers@chromium.org, Krzysztof Kozlowski , Konrad Dybcio , Srinivas Kandagatla , Satya Durga Srinivasu Prabhala , Melody Olvera , devicetree@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, Florian Fainelli , Stephen Boyd , linux-pm@vger.kernel.org, linux-arm-msm@vger.kernel.org, Elliot Berman , Elliot Berman Subject: Re: [PATCH v9 2/5] firmware: psci: Read and use vendor reset types Message-ID: References: <20250303-arm-psci-system_reset2-vendor-reboots-v9-0-b2cf4a20feda@oss.qualcomm.com> <20250303-arm-psci-system_reset2-vendor-reboots-v9-2-b2cf4a20feda@oss.qualcomm.com> <973eaca7-0632-53d8-f892-fe4d859ebbac@quicinc.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <973eaca7-0632-53d8-f892-fe4d859ebbac@quicinc.com> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20250416_050557_350556_E41E3C2D X-CRM114-Status: GOOD ( 72.72 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Wed, Apr 09, 2025 at 11:48:24PM +0530, Shivendra Pratap wrote: > > > On 4/8/2025 8:46 PM, Lorenzo Pieralisi wrote: > > On Tue, Mar 25, 2025 at 07:33:36PM +0530, Mukesh Ojha wrote: > >> On Fri, Mar 14, 2025 at 12:19:31PM +0100, Lorenzo Pieralisi wrote: > >>> On Mon, Mar 03, 2025 at 01:08:31PM -0800, Elliot Berman wrote: > >>>> From: Elliot Berman > >>>> > >>>> SoC vendors have different types of resets and are controlled through > >>>> various registers. For instance, Qualcomm chipsets can reboot to a > >>>> "download mode" that allows a RAM dump to be collected. Another example > >>>> is they also support writing a cookie that can be read by bootloader > >>>> during next boot. PSCI offers a mechanism, SYSTEM_RESET2, for these > >>>> vendor reset types to be implemented without requiring drivers for every > >>>> register/cookie. > >>>> > >>>> Add support in PSCI to statically map reboot mode commands from > >>>> userspace to a vendor reset and cookie value using the device tree. > >>> > >>> I have managed to discuss a little bit this patchset over the last > >>> few days and I think we have defined a plan going forward. > >>> > >>> A point that was raised is: > >>> > >>> https://man7.org/linux/man-pages/man2/reboot.2.html > >>> > >>> LINUX_REBOOT_CMD_RESTART2 *arg command, what is it supposed to > >>> represent ? > >>> > >>> Is it the mode the system should reboot into OR it is the > >>> actual command to be issued (which is what this patchset > >>> implements) ? > >>> > >>> LINUX_REBOOT_CMD_RESTART "..a default restart..." > >>> > >>> It is unclear what "default" means. We wonder whether the > >>> reboot_mode variable was introduced to _define_ that "default". > >>> > >>> So, in short, my aim is trying to decouple reboot_mode from the > >>> LINUX_REBOOT_CMD_RESTART2 *arg command. > >>> > >>> I believe that adding a sysfs interface to reboot-mode driver > >>> infrastructure would be useful, so that the commands would > >>> be exposed to userspace and userspace can set the *arg command > >>> specifically to issue a given reset/mode. > >>> > >>> I wonder why this is not already in place for eg syscon-reboot-mode > >>> resets, how does user space issue a command in those systems if the > >>> available commands aren't exposed to userspace ? > >>> > >>> Is there a kernel entity exposing those "modes" to userspace, somehow ? > >>> > >>>> A separate initcall is needed to parse the devicetree, instead of using > >>>> psci_dt_init because mm isn't sufficiently set up to allocate memory. > >>>> > >>>> Reboot mode framework is close but doesn't quite fit with the > >>>> design and requirements for PSCI SYSTEM_RESET2. Some of these issues can > >>>> be solved but doesn't seem reasonable in sum: > >>>> 1. reboot mode registers against the reboot_notifier_list, which is too > >>>> early to call SYSTEM_RESET2. PSCI would need to remember the reset > >>>> type from the reboot-mode framework callback and use it > >>>> psci_sys_reset. > >>>> 2. reboot mode assumes only one cookie/parameter is described in the > >>>> device tree. SYSTEM_RESET2 uses 2: one for the type and one for > >>>> cookie. > >>> > >>> This can be changed and I think it should, so that the reboot modes > >>> are exposed to user space and PSCI can use that. > >>> > >> In the case of a regular reboot or panic, the reboot/panic notifiers run > >> first, followed by the restart notifiers. The PSCI reset/reset2 should > >> be the last call from Linux, and ideally, this call should not fail. > >> > >> Reboot mode notifiers => restart notifiers or Panic notifiers => restart > >> notifiers > >> > >> So, if I understand correctly, you mean that we can change the reboot > >> mode framework to expose the arguments available to user space. We can > >> extend it to accept magic and cookies, save them in the reboot > >> framework, and retrieve them via a call from PSCI during a regular > >> reboot or panic based on the current arguments. Is this leading towards > >> writing an ARM-specific PSCI-reboot-mode driver, which in its reboot > >> notifier callback saves the magic and cookies, and these magic and > >> cookies will be used during psci_sys_reset2()? Or is there something > >> wrong with my understanding? > > > > No, you got it right (apologies for the delay in replying) - if the > > case for making reboot mode available to user space is accepted. > > > > Agree that the available modes should be exposed to usespace via sysfs interface > and we should implement it. Also #1 and #2 can be handled via some > changes in the design as mentioned in above discussion. > > I have one doubt though when we implement this via reboot-mode framework. > The current patch implements PSCI ARM PSCI SYSTEM RESET2 vendor reset types. > psci driver is initialized very early at boot but potential ARM psci reboot-mode > driver will not probe at that stage and the ARM PSCI SYSTEM RESET2 vendor reset > types functionality will not be available in psci reset path until the reboot-mode > driver probes. Will this cause any limitation on usage of ARM's PSCI vendor-reset > types for early device resets? > > One use-case may be an early device crash or a early reset where a vendor > wants to use PSCI SYSTEM RESET2 vendor reset type to a reset the device to a > specific state but may not be able to use this driver. > (eg: a kernel panic at early boot where a vendor wants to reset device > to a specific state using vendor reset. Currently panic passes a NULL > (*arg command) while device reset but it may be explored for vendor specific > reset). As you said, that would not be a PSCI only issue - *if* we wanted to plug in this use case we should find a way to do it at reboot mode driver level. As a matter of fact, this is not a mainline issue AFAICS. Even if we did not design this as a reboot mode driver there would be a time window where you would not be able to use vendor resets on panic. I don't see it as a major roadblock at the moment. Thanks, Lorenzo > > - Shivendra > > >> P.S. We appreciate Elliot for his work and follow-up on this while being > >> employed at Qualcomm. > > > > Yes I sincerely do for his patience, thank you. > > > > Lorenzo > > > >>>> 3. psci cpuidle driver already registers a driver against the > >>>> arm,psci-1.0 compatible. Refactoring would be needed to have both a > >>>> cpuidle and reboot-mode driver. > >>>> > >>>> Signed-off-by: Elliot Berman > >>>> --- > >>>> drivers/firmware/psci/psci.c | 105 +++++++++++++++++++++++++++++++++++++++++++ > >>>> 1 file changed, 105 insertions(+) > >>>> > >>>> diff --git a/drivers/firmware/psci/psci.c b/drivers/firmware/psci/psci.c > >>>> index a1ebbe9b73b136218e9d9f9b8daa7756b3ab2fbe..6f8c47deaec0225f26704e1f3bcad52603127a85 100644 > >>>> --- a/drivers/firmware/psci/psci.c > >>>> +++ b/drivers/firmware/psci/psci.c > >>>> @@ -80,6 +80,14 @@ static u32 psci_cpu_suspend_feature; > >>>> static bool psci_system_reset2_supported; > >>>> static bool psci_system_off2_hibernate_supported; > >>>> > >>>> +struct psci_reset_param { > >>>> + const char *mode; > >>>> + u32 reset_type; > >>>> + u32 cookie; > >>>> +}; > >>>> +static struct psci_reset_param *psci_reset_params __ro_after_init; > >>>> +static size_t num_psci_reset_params __ro_after_init; > >>>> + > >>>> static inline bool psci_has_ext_power_state(void) > >>>> { > >>>> return psci_cpu_suspend_feature & > >>>> @@ -306,9 +314,39 @@ static int get_set_conduit_method(const struct device_node *np) > >>>> return 0; > >>>> } > >>>> > >>>> +static int psci_vendor_system_reset2(const char *cmd) > >>>> +{ > >>>> + unsigned long ret; > >>>> + size_t i; > >>>> + > >>>> + for (i = 0; i < num_psci_reset_params; i++) { > >>>> + if (!strcmp(psci_reset_params[i].mode, cmd)) { > >>>> + ret = invoke_psci_fn(PSCI_FN_NATIVE(1_1, SYSTEM_RESET2), > >>>> + psci_reset_params[i].reset_type, > >>>> + psci_reset_params[i].cookie, 0); > >>>> + /* > >>>> + * if vendor reset fails, log it and fall back to > >>>> + * architecture reset types > >>> > >>> That's not what the code does. > >>> > >> Ack. > >> > >> -Mukesh > >> > >>>> + */ > >>>> + pr_err("failed to perform reset \"%s\": %ld\n", cmd, > >>>> + (long)ret); > >>>> + return 0; > >>>> + } > >>>> + } > >>>> + > >>>> + return -ENOENT; > >>>> +} > >>>> + > >>>> static int psci_sys_reset(struct notifier_block *nb, unsigned long action, > >>>> void *data) > >>>> { > >>>> + /* > >>>> + * try to do the vendor system_reset2 > >>>> + * If there wasn't a matching command, fall back to architectural resets > >>>> + */ > >>>> + if (data && !psci_vendor_system_reset2(data)) > >>>> + return NOTIFY_DONE; > >>>> + > >>>> if ((reboot_mode == REBOOT_WARM || reboot_mode == REBOOT_SOFT) && > >>>> psci_system_reset2_supported) { > >>>> /* > >>>> @@ -795,6 +833,73 @@ static const struct of_device_id psci_of_match[] __initconst = { > >>>> {}, > >>>> }; > >>>> > >>>> +#define REBOOT_PREFIX "mode-" > >>>> + > >>>> +static int __init psci_init_system_reset2_modes(void) > >>>> +{ > >>>> + const size_t len = strlen(REBOOT_PREFIX); > >>>> + struct psci_reset_param *param; > >>>> + struct device_node *psci_np __free(device_node) = NULL; > >>>> + struct device_node *np __free(device_node) = NULL; > >>>> + struct property *prop; > >>>> + size_t count = 0; > >>>> + u32 magic[2]; > >>>> + int num; > >>>> + > >>>> + if (!psci_system_reset2_supported) > >>>> + return 0; > >>>> + > >>>> + psci_np = of_find_matching_node(NULL, psci_of_match); > >>>> + if (!psci_np) > >>>> + return 0; > >>>> + > >>>> + np = of_find_node_by_name(psci_np, "reset-types"); > >>>> + if (!np) > >>>> + return 0; > >>> > >>> Related to my initial question above. If LINUX_REBOOT_CMD_RESTART2 *arg command, > >>> is the actual reset to be issued, should we add a default mode "cold" > >>> and, if SYSTEM_RESET2 is supported, a "warm" reset mode too ? > >>> > >>> It all boils down to what *arg represents - adding "cold" and "warm" > >>> modes would remove the dependency on reboot_mode for resets issued > >>> through LINUX_REBOOT_CMD_RESTART2, the question is whether this > >>> is the correct thing to do. > >>> > >>> Comments very welcome. > >>> > >>> Thanks, > >>> Lorenzo > >>> > >>>> + > >>>> + for_each_property_of_node(np, prop) { > >>>> + if (strncmp(prop->name, REBOOT_PREFIX, len)) > >>>> + continue; > >>>> + num = of_property_count_u32_elems(np, prop->name); > >>>> + if (num != 1 && num != 2) > >>>> + continue; > >>>> + > >>>> + count++; > >>>> + } > >>>> + > >>>> + param = psci_reset_params = > >>>> + kcalloc(count, sizeof(*psci_reset_params), GFP_KERNEL); > >>>> + if (!psci_reset_params) > >>>> + return -ENOMEM; > >>>> + > >>>> + for_each_property_of_node(np, prop) { > >>>> + if (strncmp(prop->name, REBOOT_PREFIX, len)) > >>>> + continue; > >>>> + > >>>> + num = of_property_read_variable_u32_array(np, prop->name, magic, > >>>> + 1, ARRAY_SIZE(magic)); > >>>> + if (num < 0) { > >>>> + pr_warn("Failed to parse vendor reboot mode %s\n", > >>>> + param->mode); > >>>> + kfree_const(param->mode); > >>>> + continue; > >>>> + } > >>>> + > >>>> + param->mode = kstrdup_const(prop->name + len, GFP_KERNEL); > >>>> + if (!param->mode) > >>>> + continue; > >>>> + > >>>> + /* Force reset type to be in vendor space */ > >>>> + param->reset_type = PSCI_1_1_RESET_TYPE_VENDOR_START | magic[0]; > >>>> + param->cookie = num > 1 ? magic[1] : 0; > >>>> + param++; > >>>> + num_psci_reset_params++; > >>>> + } > >>>> + > >>>> + return 0; > >>>> +} > >>>> +arch_initcall(psci_init_system_reset2_modes); > >>>> + > >>>> int __init psci_dt_init(void) > >>>> { > >>>> struct device_node *np; > >>>> > >>>> -- > >>>> 2.34.1 > >>>>