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 6D7DBC369A2 for ; Tue, 8 Apr 2025 15:19:43 +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=GAcPDD0vH+lYQQyAFtSuQmww8M9iFFcDfwx9NC0OfeI=; b=EhBhnbw8lrIQqXudTRpxU2gwwW RsN7yD/NFi730KT5p7R3UVT+6xWj+iMePzOunRV/Tuc0hxlxYt4VdLiyDan9DedzA4aEmq7abCQed Is6aPMtuaPJ90DCTwKm3vU3rZ+cQjp7y6QGvY/T7Bau2WldY82P/6lM8ySqQJGxMKYC+PFd/n73sV jshgDG+EFa9FJs7h3V4IMukKtLl4ovzUOd992xiMiZQFnpF3JLaTRfyycrED+lzP3u+bVGNXEXPk2 QsYXF/+9uh8vPgxY4ZSAwotJ7p7IZTTnmQPF5cVQIxMRLDMdkoAMTpDZxS3QUHEZkkOsRbtkfrU7d ICqysJsw==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98.1 #2 (Red Hat Linux)) id 1u2Ajc-00000004YH2-2itb; Tue, 08 Apr 2025 15:19:32 +0000 Received: from tor.source.kernel.org ([2600:3c04:e001:324:0:1991:8:25]) by bombadil.infradead.org with esmtps (Exim 4.98.1 #2 (Red Hat Linux)) id 1u2AhF-00000004Xny-0LQH for linux-arm-kernel@lists.infradead.org; Tue, 08 Apr 2025 15:17:05 +0000 Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by tor.source.kernel.org (Postfix) with ESMTP id BB109614FE; Tue, 8 Apr 2025 15:16:53 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 29D62C4CEE5; Tue, 8 Apr 2025 15:16:54 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1744125422; bh=YBHV1R1LANqwOlZ3bpGukqGWjvNFHr67D3rL1PJ5cBc=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=X92gh4MbpheXmMlisobrsJH9pTK+vbMHIiGSscsBOd56YoWUZGvQ9GHj7I9cJe6h+ 5dRHXUfyB/dxqlFo5efWZ5yeva/1Aye54sPNLiKAx3IKWSUHvzQvwQK9j124PuMPO1 Y35Yap4gT60rXG6sxYh1je5jWv5XHC2V0k8g9rvvbg5T87FCunh5tk/suoXaa7r8gb pMwBuEX3Lo7OopzWgRIar0Stmwj/J1rMPvIyQ5cKlGybubscMOgKlJHBDaRyeD8mCW 7ZjoCSUkXBiR50nZuTt8sUNYrBzIKvTY4X1U61ituZEnCC5LTi3UZCuapNVgKZV5pc cvcAxj3fXp2Ng== Date: Tue, 8 Apr 2025 17:16:52 +0200 From: Lorenzo Pieralisi To: Mukesh Ojha Cc: 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 , Shivendra Pratap , 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> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: 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 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. > 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 > > >