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Mon, 21 Aug 2023 05:09:57 GMT Received: from smtpav07.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 1817F20040; Mon, 21 Aug 2023 05:09:57 +0000 (GMT) Received: from smtpav07.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id D1CFD20043; Mon, 21 Aug 2023 05:09:52 +0000 (GMT) Received: from vajain21.in.ibm.com (unknown [9.43.51.109]) by smtpav07.fra02v.mail.ibm.com (Postfix) with SMTP; Mon, 21 Aug 2023 05:09:52 +0000 (GMT) Received: by vajain21.in.ibm.com (sSMTP sendmail emulation); Mon, 21 Aug 2023 10:39:51 +0530 From: Vaibhav Jain To: Michael Ellerman , linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org Subject: Re: [PATCH] powerpc: Enable generic cpu idle-loop In-Reply-To: <875y5cwqdb.fsf@mail.lhotse> References: <20230818050739.827851-1-vaibhav@linux.ibm.com> <875y5cwqdb.fsf@mail.lhotse> Date: Mon, 21 Aug 2023 10:39:51 +0530 Message-ID: <875y59j80w.fsf@vajain21.in.ibm.com> Content-Type: text/plain X-TM-AS-GCONF: 00 X-Proofpoint-GUID: sehh3jbzZkK2hOKOFBHYgjGE_9waUpYt X-Proofpoint-ORIG-GUID: J25pHfOH4RGd8_kNhoWGpSr2fiFWeoMR X-Proofpoint-UnRewURL: 0 URL was un-rewritten MIME-Version: 1.0 X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.267,Aquarius:18.0.957,Hydra:6.0.601,FMLib:17.11.176.26 definitions=2023-08-20_15,2023-08-18_01,2023-05-22_02 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 spamscore=0 impostorscore=0 mlxscore=0 malwarescore=0 mlxlogscore=865 lowpriorityscore=0 suspectscore=0 phishscore=0 bulkscore=0 priorityscore=1501 adultscore=0 clxscore=1015 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2306200000 definitions=main-2308210047 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: , Cc: "Paul E. McKenney" , Jonathan Corbet , Peter Zijlstra , Catalin Marinas , Randy Dunlap , "Steven Rostedt \(Google\)" , Nicholas Piggin , Vaidyanathan Srinivasan , Daniel Sneddon Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" Thanks for looking at this patch Mpe. Michael Ellerman writes: > Vaibhav Jain writes: >> This minor patch enables config option GENERIC_IDLE_POLL_SETUP for arch >> powerpc. This should add support for kernel param 'nohlt'. > > Which is named after an 8086 instruction :), but oh well. > Thanks. This is an interesting trivia :) >> Powerpc kernel also supports another kernel boot-time param called >> 'powersave' which can also be used to disable all cpu idle-states and >> forces CPU to an idle-loop similar to what cpu_idle_poll() does. This >> patch however makes powerpc kernel-parameters better aligned to the >> generic boot-time parameters. > > It would be nice if we could make our powersave=off parameter just > enable this generic logic. > > Have you looked at if that's possible? At a glance it looks like it > should be, when cpu_idle_force_poll is true do_idle() never calls > cpuidle_idle_call(), so the cpuidle drivers are never invoked. Thanks for suggesting this and it looks like a simple fix to arch/idle.c code. I have posted a v2 with the needed change on the mailing list at https://lore.kernel.org/all/20230821045928.1350893-1-vaibhav@linux.ibm.com -- Cheers ~ Vaibhav