From patchwork Mon Jan 6 11:11:39 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Pratik R. 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Violators will be prosecuted; (version=TLSv1/SSLv3 cipher=AES256-GCM-SHA384 bits=256/256) Mon, 6 Jan 2020 11:11:46 -0000 Received: from d06av21.portsmouth.uk.ibm.com (d06av21.portsmouth.uk.ibm.com [9.149.105.232]) by b06cxnps4074.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id 006BBilR22347892 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Mon, 6 Jan 2020 11:11:44 GMT Received: from d06av21.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 6084E5204E; Mon, 6 Jan 2020 11:11:44 +0000 (GMT) Received: from pratiks-thinkpad.in.ibm.com (unknown [9.124.31.198]) by d06av21.portsmouth.uk.ibm.com (Postfix) with ESMTP id C8CFA5204F; Mon, 6 Jan 2020 11:11:42 +0000 (GMT) From: Pratik Rajesh Sampat To: linux-kernel@vger.kernel.org, linuxppc-dev@ozlabs.org, mpe@ellerman.id.au, svaidy@linux.ibm.com, ego@linux.vnet.ibm.com, linuxram@us.ibm.com, psampat@linux.ibm.com, pratik.sampat@in.ibm.com, pratik.r.sampat@gmail.com Subject: [PATCH v2 0/3] Introduce Self-Save API for deep stop states Date: Mon, 6 Jan 2020 16:41:39 +0530 X-Mailer: git-send-email 2.24.1 MIME-Version: 1.0 X-TM-AS-GCONF: 00 x-cbid: 20010611-0008-0000-0000-00000346DEB9 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 20010611-0009-0000-0000-00004A671CFD Message-Id: X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.95, 18.0.572 definitions=2020-01-06_04:2020-01-06, 2020-01-06 signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 lowpriorityscore=0 impostorscore=0 mlxscore=0 clxscore=1015 phishscore=0 spamscore=0 priorityscore=1501 suspectscore=0 bulkscore=0 adultscore=0 mlxlogscore=857 malwarescore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-1910280000 definitions=main-2001060102 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" RFC v1 patches: https://lkml.org/lkml/2019/12/4/193 Changelog RFC v1 --> v2 1. Optimized preference bitmask 2. Addressed comments from Ram Pai 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 arch/powerpc/include/asm/opal-api.h | 3 +- arch/powerpc/include/asm/opal.h | 1 + arch/powerpc/platforms/powernv/idle.c | 433 ++++++++++++++++++--- arch/powerpc/platforms/powernv/opal-call.c | 1 + 4 files changed, 381 insertions(+), 57 deletions(-)