From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp.subspace.kernel.org (Postfix) with ESMTP id EF7B914EC42; Wed, 19 Jun 2024 13:51:49 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=217.140.110.172 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1718805113; cv=none; b=an2rjnLn0X1kyuYBlJq5Z5Gj7aT+ltGRGej4byk//rLoL1tHOcN4Eyh02SspIm6orWilk8WLuNylVEqh4UNSzLhGtKW2WVA3E185tpJEDfD4jy89h1s36uEuLGTN+RpdpGmB0QxM7qnICbFIk12kEPL9wF1FAOdx3VcURL8g/FU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1718805113; c=relaxed/simple; bh=NcbVL8HU9Je49lLwp3mfyuRCxqqP6v2o4zytyBE5jB4=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=LLUjo3grT+yskJ+D5TLGQ/H+qa6FoRY2iv8Wv1pM6ycnKk4nqVd5PMqcEmrw+9N9ygKPWlwylUbIZ76l5P80r9ix27gmQspSPcu1cE0xYcWvfBynnoESW8KqJ090d3PxHm7+cV2E6zXc5FBq8KS8ZrlJMkx3Yo8CyW/RdSpmXSM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com; spf=pass smtp.mailfrom=arm.com; arc=none smtp.client-ip=217.140.110.172 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=arm.com Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id CB8071042; Wed, 19 Jun 2024 06:52:13 -0700 (PDT) Received: from bogus (unknown [10.57.89.235]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 990903F6A8; Wed, 19 Jun 2024 06:51:44 -0700 (PDT) Date: Wed, 19 Jun 2024 14:51:43 +0100 From: Sudeep Holla To: Elliot Berman Cc: Bjorn Andersson , Sudeep Holla , Konrad Dybcio , Sebastian Reichel , Rob Herring , Krzysztof Kozlowski , Conor Dooley , Vinod Koul , Andy Yan , Lorenzo Pieralisi , Mark Rutland , Bartosz Golaszewski , 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 , linux-pm@vger.kernel.org, linux-arm-msm@vger.kernel.org Subject: Re: [PATCH v5 3/4] firmware: psci: Read and use vendor reset types Message-ID: <20240619135143.kr2tx4ynxayc5v3a@bogus> References: <20240617-arm-psci-system_reset2-vendor-reboots-v5-0-086950f650c8@quicinc.com> <20240617-arm-psci-system_reset2-vendor-reboots-v5-3-086950f650c8@quicinc.com> Precedence: bulk X-Mailing-List: devicetree@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20240617-arm-psci-system_reset2-vendor-reboots-v5-3-086950f650c8@quicinc.com> On Mon, Jun 17, 2024 at 10:18:09AM -0700, Elliot Berman wrote: > 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. > > 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. > 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. > I need to think through it but when you first introduced the generic Documentation/devicetree/bindings/power/reset/reboot-mode.yaml bindings I also looked at drivers/power/reset/reboot-mode.c I assumed this extension to that binding would reuse the same and PSCI would just do reboot_mode_register(). I didn't expect to see these changes. I might have missing something but since the bindings is still quite generic with additional cells that act as additional cookie for reboot call, I still think that should be possible. What am I missing here then ? -- Regards, Sudeep