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Violators will be prosecuted; (version=TLSv1/SSLv3 cipher=AES256-GCM-SHA384 bits=256/256) Tue, 17 Mar 2020 14:10:21 -0000 Received: from d06av25.portsmouth.uk.ibm.com (d06av25.portsmouth.uk.ibm.com [9.149.105.61]) by b06cxnps4075.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id 02HEAKLb57147470 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Tue, 17 Mar 2020 14:10:21 GMT Received: from d06av25.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id C8ED211C052; Tue, 17 Mar 2020 14:10:20 +0000 (GMT) Received: from d06av25.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 5B82B11C058; Tue, 17 Mar 2020 14:10:19 +0000 (GMT) Received: from pratiks-thinkpad.ibmuc.com (unknown [9.199.61.203]) by d06av25.portsmouth.uk.ibm.com (Postfix) with ESMTP; Tue, 17 Mar 2020 14:10:19 +0000 (GMT) From: Pratik Rajesh Sampat To: linux-kernel@vger.kernel.org, linuxppc-dev@ozlabs.org, mpe@ellerman.id.au, ego@linux.vnet.ibm.com, linuxram@us.ibm.com, psampat@in.ibm.com, pratik.r.sampat@gmail.com Subject: [PATCH v5 0/3] Introduce Self-Save API for deep stop states Date: Tue, 17 Mar 2020 19:40:15 +0530 X-Mailer: git-send-email 2.24.1 MIME-Version: 1.0 X-TM-AS-GCONF: 00 x-cbid: 20031714-4275-0000-0000-000003ADD591 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 20031714-4276-0000-0000-000038C2FEA0 Message-Id: <20200317141018.42380-1-psampat@linux.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.138, 18.0.645 definitions=2020-03-17_05:2020-03-17, 2020-03-17 signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 spamscore=0 suspectscore=0 phishscore=0 clxscore=1015 malwarescore=0 lowpriorityscore=0 mlxscore=0 mlxlogscore=999 adultscore=0 impostorscore=0 priorityscore=1501 bulkscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2003020000 definitions=main-2003170059 X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: linuxppc-dev-bounces+patchwork-incoming=ozlabs.org@lists.ozlabs.org Sender: "Linuxppc-dev" Skiboot patches v4: https://lists.ozlabs.org/pipermail/skiboot/2020-February/016404.html Linux patches v4: https://lkml.org/lkml/2020/2/12/446 Changelog v4 --> v5 Based on Michael Ellerman's comments, in patch3: 1. Added documentation in power-mgt.txt for self-save and self-restore 2. Used bitmap abstractions while parsing device tree 3. Fixed scenario where zero or less SPRs were treated as a success 4. Removed redundant device_node pointer 5. Removed unnecessary pr_warn messages 6. Changed the old of_find_node_by_path calls to of_find_compatible_node 7. Fixed leaking reference of the parsed device_node pointer Currently the stop-API supports a mechanism called as self-restore which allows us to restore the values of certain SPRs on wakeup from a deep-stop state to a desired value. To use this, the Kernel makes an OPAL call passing the PIR of the CPU, the SPR number and the value to which the SPR should be restored when that CPU wakes up from a deep stop state. Recently, a new feature, named self-save has been enabled in the stop-api, which is an alternative mechanism to do the same, except that self-save will save the current content of the SPR before entering a deep stop state and also restore the content back on waking up from a deep stop state. This patch series aims at introducing and leveraging the self-save feature in the kernel. Now, as the kernel has a choice to prefer one mode over the other and there can be registers in both the save/restore SPR list which are sent from the device tree, a new interface has been defined for the seamless handing of the modes for each SPR. A list of preferred SPRs are maintained in the kernel which contains two properties: 1. supported_mode: Helps in identifying if it strictly supports self save or restore or both. Initialized using the information from device tree. 2. preferred_mode: Calls out what mode is preferred for each SPR. It could be strictly self save or restore, or it can also determine the preference of mode over the other if both are present by encapsulating the other in bitmask from LSB to MSB. Initialized statically. Below is a table to show the Scenario::Consequence when the self save and self restore modes are available or disabled in different combinations as perceived from the device tree thus giving complete backwards compatibly regardless of an older firmware running a newer kernel or vise-versa. Support for self save or self-restore is embedded in the device tree, along with the set of registers it supports. SR = Self restore; SS = Self save .-----------------------------------.----------------------------------------. | Scenario | Consequence | :-----------------------------------+----------------------------------------: | Legacy Firmware. No SS or SR node | Self restore is called for all | | | supported SPRs | :-----------------------------------+----------------------------------------: | SR: !active SS: !active | Deep stop states disabled | :-----------------------------------+----------------------------------------: | SR: active SS: !active | Self restore is called for all | | | supported SPRs | :-----------------------------------+----------------------------------------: | SR: active SS: active | Goes through the preferences for each | | | SPR and executes of the modes | | | accordingly. Currently, Self restore is| | | called for all the SPRs except PSSCR | | | which is self saved | :-----------------------------------+----------------------------------------: | SR: active(only HID0) SS: active | Self save called for all supported | | | registers expect HID0 (as HID0 cannot | | | be self saved currently) | :-----------------------------------+----------------------------------------: | SR: !active SS: active | currently will disable deep states as | | | HID0 is needed to be self restored and | | | cannot be self saved | '-----------------------------------'----------------------------------------' Pratik Rajesh Sampat (3): powerpc/powernv: Interface to define support and preference for a SPR powerpc/powernv: Introduce Self save support powerpc/powernv: Parse device tree, population of SPR support .../bindings/powerpc/opal/power-mgt.txt | 10 + arch/powerpc/include/asm/opal-api.h | 3 +- arch/powerpc/include/asm/opal.h | 1 + arch/powerpc/platforms/powernv/idle.c | 416 +++++++++++++++--- arch/powerpc/platforms/powernv/opal-call.c | 1 + 5 files changed, 373 insertions(+), 58 deletions(-)