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 F2F9719D077; Mon, 24 Jun 2024 15:41:47 +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=1719243710; cv=none; b=eIv2j73BcB/zsLuGJ3xvS3Z1+cXDNkU26u6Z/PYZPDJhOVpEmyKQjHBU8KCJ9W0jXX0j95FElRXMtI18EQja6azrxFJTNPGBRJ5V6Flab0PDzhV1yIHNW94/QzdTHungAKSCTSY0E4SYuDx515QHtI7eRBAuFVTNq0J4nf4ffS0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1719243710; c=relaxed/simple; bh=3dz1GFXIvgH5i6DZjwGNKWeBzYGIWxh02+vy/2Ekez0=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=kpvdlEZdkdz7Qe71SRdi/2q+uVAcKAQ4qisRuHD8tTLkKsSNFjAIFTUhEbXh/3hvVmmKVqlBFTuGZ10NTaKcr31OXcrqLjW1Z2NzI6bnRvHEsQTvAfzBZT479tq2mN5+egFulauqiolx8qaAZf8+1Bf2pz5ky6ss2OIX1fudrzs= 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 1A71DDA7; Mon, 24 Jun 2024 08:42:12 -0700 (PDT) Received: from bogus (e103737-lin.cambridge.arm.com [10.1.197.49]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 9DD2D3F73B; Mon, 24 Jun 2024 08:41:44 -0700 (PDT) Date: Mon, 24 Jun 2024 16:41:42 +0100 From: Sudeep Holla To: Elliot Berman Cc: Sebastian Reichel , Sudeep Holla , Bjorn Andersson , Konrad Dybcio , Rob Herring , Krzysztof Kozlowski , Conor Dooley , Vinod Koul , Andy Yan , Lorenzo Pieralisi , "Mark Rutland" , Bartosz Golaszewski , Satya Durga Srinivasu Prabhala , Melody Olvera , Shivendra Pratap , , , , Florian Fainelli , , Subject: Re: [PATCH v5 3/4] firmware: psci: Read and use vendor reset types Message-ID: 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> <20240619135143.kr2tx4ynxayc5v3a@bogus> <20240619080933071-0700.eberman@hu-eberman-lv.qualcomm.com> <20240620162547309-0700.eberman@hu-eberman-lv.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=us-ascii Content-Disposition: inline In-Reply-To: <20240620162547309-0700.eberman@hu-eberman-lv.qualcomm.com> On Thu, Jun 20, 2024 at 04:37:09PM -0700, Elliot Berman wrote: > Hi Sudeep and Sebastian, > > On Wed, Jun 19, 2024 at 08:28:06AM -0700, Elliot Berman wrote: > > On Wed, Jun 19, 2024 at 02:51:43PM +0100, Sudeep Holla wrote: > > > 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 ? > > > > > > > Right, if that was only thing to "solve" to make it easy to use > > reboot-mode framework, I agree we should update reboot mode framework to > > work with the additional cells. There are a few other issues I mention > > above which, when combined, make me feel that PSCI is different enough > > from how reboot mode framework works that we shouldn't try to make PSCI > > work with the framework. Issues #1 and #2 are pretty easy to solve > > (whether they should be solved is different); I'm not sure a good > > approach to issue #3. > > > > Does the reasoning I mention in the commit text make sense why PSCI should > avoid using the reboot-mode.c framework? Sorry, I completely missed to see that you had already answered those in your commit message. As mentioned earlier I haven't looked at the reboot mode framework completely yet, so I can't comment on it yet. I don't want to be blocker though if others are happy with this. -- Regards, Sudeep