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Wed, 26 Aug 2020 09:40:12 +0000 (GMT) Received: from drishya.in.ibm.com (unknown [9.199.54.64]) by d06av21.portsmouth.uk.ibm.com (Postfix) with ESMTPS id 55DA052054; Wed, 26 Aug 2020 09:40:11 +0000 (GMT) Date: Wed, 26 Aug 2020 15:10:09 +0530 From: Vaidyanathan Srinivasan To: Pratik Rajesh Sampat Subject: Re: [PATCH] Revert "powerpc/powernv/idle: Replace CPU feature check with PVR check" Message-ID: <20200826094009.GC48285@drishya.in.ibm.com> References: <20200826082918.89306-1-psampat@linux.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline In-Reply-To: <20200826082918.89306-1-psampat@linux.ibm.com> X-TM-AS-GCONF: 00 X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.235, 18.0.687 definitions=2020-08-26_06:2020-08-25, 2020-08-26 signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 phishscore=0 spamscore=0 impostorscore=0 mlxscore=0 lowpriorityscore=0 priorityscore=1501 adultscore=0 bulkscore=0 clxscore=1011 suspectscore=0 malwarescore=0 mlxlogscore=999 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2006250000 definitions=main-2008260075 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: , Reply-To: svaidy@linux.ibm.com Cc: ego@linux.vnet.ibm.com, mikey@neuling.org, pratik.r.sampat@gmail.com, linux-kernel@vger.kernel.org, npiggin@gmail.com, linuxppc-dev@lists.ozlabs.org Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" * Pratik Rajesh Sampat [2020-08-26 13:59:18]: > Cpuidle stop state implementation has minor optimizations for P10 > where hardware preserves more SPR registers compared to P9. > The current P9 driver works for P10, although does few extra > save-restores. P9 driver can provide the required power management > features like SMT thread folding and core level power savings > on a P10 platform. > > Until the P10 stop driver is available, revert the commit which > allows for only P9 systems to utilize cpuidle and blocks all > idle stop states for P10. > Cpu idle states are enabled and tested on the P10 platform > with this fix. > > This reverts commit 8747bf36f312356f8a295a0c39ff092d65ce75ae. > > Fixes: 8747bf36f312 ("powerpc/powernv/idle: Replace CPU feature check with PVR check") > Signed-off-by: Pratik Rajesh Sampat Reviewed-by: Vaidyanathan Srinivasan > --- > @mpe: This revert would resolve a staging issue wherein the P10 stop > driver is not yet ready while cpuidle stop states need not be blocked > on 5.9 for Power10 systems which could cause SMT folding related > performance issues. > > The P10 stop driver is in the works here: > https://lists.ozlabs.org/pipermail/linuxppc-dev/2020-August/216773.html > > arch/powerpc/platforms/powernv/idle.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/arch/powerpc/platforms/powernv/idle.c b/arch/powerpc/platforms/powernv/idle.c > index 77513a80cef9..345ab062b21a 100644 > --- a/arch/powerpc/platforms/powernv/idle.c > +++ b/arch/powerpc/platforms/powernv/idle.c > @@ -1223,7 +1223,7 @@ static void __init pnv_probe_idle_states(void) > return; > } > > - if (pvr_version_is(PVR_POWER9)) > + if (cpu_has_feature(CPU_FTR_ARCH_300)) > pnv_power9_idle_init(); > > for (i = 0; i < nr_pnv_idle_states; i++) This revert solves the stated problem and makes kernel v5.9 work reasonable well on P10 with stop states which are required for SMT mode changes. Complete P10 driver has been in the works and will build on this fix and complete the required platform support and optimizations. --Vaidy