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Fri, 10 Jul 2026 11:57:01 -0700 (PDT) X-Received: by 2002:a05:6a20:c998:b0:3c0:9c1a:893f with SMTP id adf61e73a8af0-3c110f7f555mr201789637.71.1783709821554; Fri, 10 Jul 2026 11:57:01 -0700 (PDT) Received: from localhost ([50.35.46.84]) by smtp.gmail.com with ESMTPSA id 5a478bee46e88-311747f5975sm40499805eec.4.2026.07.10.11.56.59 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 10 Jul 2026 11:57:00 -0700 (PDT) Date: Fri, 10 Jul 2026 11:56:56 -0700 From: Jonathan Cameron To: Andre Przywara Cc: Lorenzo Pieralisi , Hanjun Guo , Sudeep Holla , Catalin Marinas , Will Deacon , "Rafael J . Wysocki" , Len Brown , James Morse , Ben Horgan , Reinette Chatre , Fenghua Yu , Jonathan Cameron , Srivathsa L Rao , Ganapatrao Kulkarni , Trilok Soni , Srinivas Ramana , Niyas Sait , linux-acpi@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v3 07/16] arm_mpam: __ris_msmon_read(): get rid of nrdy special handling Message-ID: <20260710115656.00001345@oss.qualcomm.com> In-Reply-To: <20260710144520.917375-8-andre.przywara@arm.com> References: <20260710144520.917375-1-andre.przywara@arm.com> <20260710144520.917375-8-andre.przywara@arm.com> Organization: Qualcomm X-Mailer: Claws Mail 4.4.0 (GTK 3.24.51; x86_64-w64-mingw32) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Proofpoint-Spam-Info: AW1haW4tMjYwNzEwMDE4OSBTYWx0ZWRfX8PM9jQ8o3mYn 6K7T6UmqHJmLhkixE43sKWNxp1dCREEo8bm7uODLQKliJ2vU6aCDvO6/OQhLE+/9D144vP0G0bb tr/NKrJw8fCjwdc2cuOT43k7lBolDgw= X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwNzEwMDE4OSBTYWx0ZWRfX/ug0tfKOjVaU tkjjVhMWdhrygeNdPNeeRpolMC3dA7zoNldYd8/9wFyM+hHakuuo1zoGIXjwAzNBgQoIS0ifscP FRMEpEP+WfbvvimXCjMTjrZqUULXx/SFKXHo3Vc+on2TKbLeFQ2VVt3jHx9+johs63WhO5iyaA6 4iJstajq5qUrsghyuahEPeVo5loiipwFjpQv6AcXSBR4AsaV8+8h4bFdCf80UD2rC9YOBwQ0Kt0 G6kdws0NftJ19EN060H0F24rPKyV0zT8wGA5154AVUT4FI84d0/isjb4F+f1VLPLlVqQ4k5GG1u 5blJQ0mjV5mFpSWxbz1732oVaw+BnoEjFOA1YwSU57Sq8EQkByhCZtcO8acp0Gx/GQ6BaQVWZE3 29a4hGoJWjwXPWv1K5Kf3Dt4MsQE8lXDEn9RGvzePKXBbDTSJr84Z9xOuqeuVQLT0A9fSqh4zvP 2SagV5QHuNNBOz4mkyw== X-Proofpoint-GUID: y5iihj_SqT1FhqzE_-R0ZAjMA-7ZG0l8 X-Proofpoint-ORIG-GUID: y5iihj_SqT1FhqzE_-R0ZAjMA-7ZG0l8 X-Authority-Analysis: v=2.4 cv=M/x97Sws c=1 sm=1 tr=0 ts=6a514083 cx=c_pps a=Qgeoaf8Lrialg5Z894R3/Q==:117 a=qC1CW/w66vtJz1P9yTJxNA==:17 a=kj9zAlcOel0A:10 a=RAioF0-LDSMA:10 a=s4-Qcg_JpJYA:10 a=VkNPw1HP01LnGYTKEx00:22 a=u7WPNUs3qKkmUXheDGA7:22 a=YMgV9FUhrdKAYTUUvYB2:22 a=7CQSdrXTAAAA:8 a=TeALGT1HamTeR9oYe0QA:9 a=CjuIK1q_8ugA:10 a=x9snwWr2DeNwDh03kgHS:22 a=a-qgeE7W1pNrGK8U0ZQC:22 X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1143,Hydra:6.1.134,FMLib:17.12.100.49 definitions=2026-07-10_05,2026-07-10_01,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 lowpriorityscore=0 adultscore=0 bulkscore=0 malwarescore=0 suspectscore=0 phishscore=0 spamscore=0 clxscore=1015 priorityscore=1501 impostorscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2606150000 definitions=main-2607100189 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.9.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260710_115710_847017_675A8627 X-CRM114-Status: GOOD ( 30.63 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Fri, 10 Jul 2026 16:45:11 +0200 Andre Przywara wrote: > Although so far MSC accesses couldn't fail, there is one special > condition that would create an error: when the MBWU counter wouldn't be > able to read a stable value, we were setting bit 63 to mark this value > as unstable, and return this as an error later. > Now since the functions can return a proper error value, we can get rid of > this kludge and use the return value directly. > > Remove the "nrdy" error flag variable, and assign -EBUSY to "ret" to handle > this case. > > Signed-off-by: Andre Przywara Hi Andre I'm still fussing about code flow and style :( Obviously none of this is that important, but it does help make the code more maintainable in the long run. Jonathan > --- > drivers/resctrl/mpam_devices.c | 38 +++++++++++++++------------------- > 1 file changed, 17 insertions(+), 21 deletions(-) > > diff --git a/drivers/resctrl/mpam_devices.c b/drivers/resctrl/mpam_devices.c > index 84a8715464be..530ac0fe97b5 100644 > --- a/drivers/resctrl/mpam_devices.c > +++ b/drivers/resctrl/mpam_devices.c > @@ -1306,7 +1306,6 @@ static void __ris_msmon_read(void *arg) > u64 now; > int ret; > u32 now32; > - bool nrdy = false; > bool config_mismatch; > bool overflow = false; > struct mon_read *m = arg; > @@ -1371,14 +1370,18 @@ static void __ris_msmon_read(void *arg) > switch (m->type) { > case mpam_feat_msmon_csu: > ret = mpam_read_monsel_reg(msc, CSU, &now32); > + if (!ret) { > + if ((now32 & MSMON___NRDY)) > + ret = -EBUSY; > + > + if (mpam_has_quirk(IGNORE_CSU_NRDY, msc) && > + m->waited_timeout) > + ret = 0; Whilst it is from existing code, this pattern of set and error then clear it is less than ideal. Maybe if ((now32 & MSMON___NRDY) && !(mpam_has_quirk(IGNORE_CS_NRDY, MSC && m->waited_timeout)) ret = -EBUSY; is clearer as that odd intermediate state of ret never happens. > + } > if (ret) > goto out_unlock; > - nrdy = now32 & MSMON___NRDY; > - now = FIELD_GET(MSMON___VALUE, now32); > - > - if (mpam_has_quirk(IGNORE_CSU_NRDY, msc) && m->waited_timeout) > - nrdy = false; > > + now = FIELD_GET(MSMON___VALUE, now32); > break; > case mpam_feat_msmon_mbwu_31counter: > case mpam_feat_msmon_mbwu_44counter: > @@ -1394,9 +1397,11 @@ static void __ris_msmon_read(void *arg) > now = FIELD_GET(MSMON___L_VALUE, now); > } else { > ret = mpam_read_monsel_reg(msc, MBWU, &now32); > + if (!ret && (now32 & MSMON___NRDY)) > + ret = -EBUSY; > if (ret) > goto out_unlock; > - nrdy = now32 & MSMON___NRDY; > + > now = FIELD_GET(MSMON___VALUE, now32); > } > > @@ -1404,9 +1409,6 @@ static void __ris_msmon_read(void *arg) > m->type != mpam_feat_msmon_mbwu_63counter) > now *= 64; > > - if (nrdy) > - break; > - > mbwu_state = &ris->mbwu_state[ctx->mon]; > > if (overflow) > @@ -1419,22 +1421,16 @@ static void __ris_msmon_read(void *arg) > now += mbwu_state->correction; > break; > default: > - m->err = -EINVAL; > + ret = -EINVAL; > } > - mpam_mon_sel_unlock(msc); > - > - if (nrdy) > - m->err = -EBUSY; > - > - if (!m->err) > - *m->val += now; > - > - return; > > out_unlock: > mpam_mon_sel_unlock(msc); > > - m->err = ret; > + if (ret) > + m->err = ret; > + else > + *m->val += now; If you do the earlier suggestion of ACQUIRE() this all get simpler, but if you do keep this, then burn a line or two of code to make it obvious what is error and what isn't. if (ret) { m->err = ret; return; } *m->val += now; > }