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 9FDE8C282EC for ; Fri, 14 Mar 2025 11:30:18 +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=lsMqkIj6X9Ksraxyiyv0PPQiVt9JWGsjKjXFZZVZW/M=; b=GVOLyglbljlQLHy9pi6HWriusT RDSggYxQMU3aFLLZM9ZuIQiXTVuBarPKjfUOevb5/JJbqwjTnX/g5ynjwGC4E+kmmCiinGvEIx74O w9WWZCiaSX0w8tdQOdxMCk+62x+uymdikJ5WN+b3ccZpcgyclCZF5aoK+nR8y5x6wZcon5yCqi/yY 6ZGU/VgXqjGbsjSBg21SnuCHlv7vDEAtCHre+rqfNxZH0LvSpz9WWFgwk1XtDv2ePPvqkgzrYYx1U Uo50QCIwLFpJeu0fIRf/3MDW4B/C5uTPbSJZZ60ECXXjSl0OzPDe0DUOeiGQkwT5OAgrNkrCr3pZw +gBf7n+A==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98 #2 (Red Hat Linux)) id 1tt3Ev-0000000E0EX-0OzD; Fri, 14 Mar 2025 11:30:09 +0000 Received: from nyc.source.kernel.org ([2604:1380:45d1:ec00::3]) by bombadil.infradead.org with esmtps (Exim 4.98 #2 (Red Hat Linux)) id 1tt34r-0000000Dyp0-0ck8 for linux-arm-kernel@lists.infradead.org; Fri, 14 Mar 2025 11:19:46 +0000 Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by nyc.source.kernel.org (Postfix) with ESMTP id 190CCA45598; Fri, 14 Mar 2025 11:14:14 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id A0C6BC4CEE9; Fri, 14 Mar 2025 11:19:34 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1741951183; bh=oqVgxdpTP6G2PaiGKfQC4A75YZyp+n3zWNLGzhZi3Ok=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=mjjMhDN6TgO6LGNUdqHBc4gzpfwcgKKS0B58OrCbfyJQMPpXv5ytGjdGwIdnFkB/J f1zPN4QTih0sP9PEytu5yT3wL2hKPfTosDCTUaEaZ10Y9Vh9WW32Y2xUqva2Sb5oF9 KkdiNSLOoiiN5gXEJHzJEy7oWr8SmzETnbusOqHG/ljSsMhXeyHwc3ImmAh0Im0BjF VF1NJulcguYsWchdK5C4fDd82G3u+CXXwGNxFbjx5+uQAfYmncHo8cxA/Wafmi3gFF Md8P90ysNU7Dfb+mm0ije8hK0pWr0i93VwfwPv0fmUnk2dnf87LZ/BYKu2sNwCItCp 3hsJvf4YkeqDg== Date: Fri, 14 Mar 2025 12:19:31 +0100 From: Lorenzo Pieralisi To: Elliot Berman Cc: 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: <20250303-arm-psci-system_reset2-vendor-reboots-v9-2-b2cf4a20feda@oss.qualcomm.com> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20250314_041945_317253_7D569FF5 X-CRM114-Status: GOOD ( 47.82 ) 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 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. > 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. > + */ > + 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 >