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[110.174.173.27]) by smtp.gmail.com with ESMTPSA id o8sm12166432pgb.23.2020.07.12.22.52.36 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 12 Jul 2020 22:52:37 -0700 (PDT) Date: Mon, 13 Jul 2020 15:52:32 +1000 From: Nicholas Piggin Subject: Re: [PATCH v2 2/3] powerpc/powernv/idle: save-restore DAWR0, DAWRX0 for P10 To: benh@kernel.crashing.org, ego@linux.vnet.ibm.com, linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, mikey@neuling.org, mpe@ellerman.id.au, paulus@samba.org, pratik.r.sampat@gmail.com, Pratik Rajesh Sampat , ravi.bangoria@linux.ibm.com, svaidy@linux.ibm.com References: <20200710052207.12003-1-psampat@linux.ibm.com> <20200710052207.12003-3-psampat@linux.ibm.com> In-Reply-To: <20200710052207.12003-3-psampat@linux.ibm.com> MIME-Version: 1.0 Message-Id: <1594619458.45vrahx59w.astroid@bobo.none> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Excerpts from Pratik Rajesh Sampat's message of July 10, 2020 3:22 pm: > Additional registers DAWR0, DAWRX0 may be lost on Power 10 for > stop levels < 4. > Therefore save the values of these SPRs before entering a "stop" > state and restore their values on wakeup. Hmm, where do you get this from? Documentation I see says DAWR is lost on POWER9 but not P10. Does idle thread even need to save DAWR, or does it get switched when going to a thread that has a watchpoint set? Thanks, Nick >=20 > Signed-off-by: Pratik Rajesh Sampat > --- > arch/powerpc/platforms/powernv/idle.c | 10 ++++++++++ > 1 file changed, 10 insertions(+) >=20 > diff --git a/arch/powerpc/platforms/powernv/idle.c b/arch/powerpc/platfor= ms/powernv/idle.c > index 19d94d021357..f2e2a6a4c274 100644 > --- a/arch/powerpc/platforms/powernv/idle.c > +++ b/arch/powerpc/platforms/powernv/idle.c > @@ -600,6 +600,8 @@ struct p9_sprs { > u64 iamr; > u64 amor; > u64 uamor; > + u64 dawr0; > + u64 dawrx0; > }; > =20 > static unsigned long power9_idle_stop(unsigned long psscr, bool mmu_on) > @@ -687,6 +689,10 @@ static unsigned long power9_idle_stop(unsigned long = psscr, bool mmu_on) > sprs.iamr =3D mfspr(SPRN_IAMR); > sprs.amor =3D mfspr(SPRN_AMOR); > sprs.uamor =3D mfspr(SPRN_UAMOR); > + if (cpu_has_feature(CPU_FTR_ARCH_31)) { > + sprs.dawr0 =3D mfspr(SPRN_DAWR0); > + sprs.dawrx0 =3D mfspr(SPRN_DAWRX0); > + } > =20 > srr1 =3D isa300_idle_stop_mayloss(psscr); /* go idle */ > =20 > @@ -710,6 +716,10 @@ static unsigned long power9_idle_stop(unsigned long = psscr, bool mmu_on) > mtspr(SPRN_IAMR, sprs.iamr); > mtspr(SPRN_AMOR, sprs.amor); > mtspr(SPRN_UAMOR, sprs.uamor); > + if (cpu_has_feature(CPU_FTR_ARCH_31)) { > + mtspr(SPRN_DAWR0, sprs.dawr0); > + mtspr(SPRN_DAWRX0, sprs.dawrx0); > + } > =20 > /* > * Workaround for POWER9 DD2.0, if we lost resources, the ERAT > --=20 > 2.25.4 >=20 >=20