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[103.229.16.4]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-8569f49e3bfsm3075779b3a.9.2026.08.30.22.43.36 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Sun, 30 Aug 2026 22:43:41 -0700 (PDT) Message-ID: <0cb5eddd-2422-4ccd-aa42-34b46086491f@oss.qualcomm.com> Date: Mon, 31 Aug 2026 13:43:34 +0800 Precedence: bulk X-Mailing-List: devicetree@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH RFC 02/15] cacheinfo: Expose the code to generate a cache-id from a device_node To: Drew Fustini Cc: "Rafael J. Wysocki" , Shanker Donthineni , Conor Dooley , Fenghua Yu , Krzysztof Kozlowski , Rob Herring , Reinette Chatre , Konrad Dybcio , James Morse , Ben Horgan , Bjorn Andersson , Danilo Krummrich , Greg Kroah-Hartman , linux-arm-msm@vger.kernel.org, ganapatrao.kulkarni@oss.qualcomm.com, trilok.soni@oss.qualcomm.com, devicetree@vger.kernel.org, driver-core@lists.linux.dev, Srivathsa L Rao , Huang Yiwei , aiqun.yu@oss.qualcomm.com, linux-kernel@vger.kernel.org References: <20260811-mpam-resctrl-dt-knp-support-v1-0-ea6397bead59@oss.qualcomm.com> <20260811-mpam-resctrl-dt-knp-support-v1-2-ea6397bead59@oss.qualcomm.com> Content-Language: en-US From: Yin Li In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Authority-Analysis: v=2.4 cv=DY0nbPtW c=1 sm=1 tr=0 ts=6a95148f cx=c_pps a=rEQLjTOiSrHUhVqRoksmgQ==:117 a=nuhDOHQX5FNHPW3J6Bj6AA==:17 a=NSEGM1D4AEf8_kYA:21 a=IkcTkHD0fZMA:10 a=Sv0fKeRqtYgA:10 a=s4-Qcg_JpJYA:10 a=VkNPw1HP01LnGYTKEx00:22 a=u7WPNUs3qKkmUXheDGA7:22 a=eoimf2acIAo5FJnRuUoq:22 a=VwQbUJbxAAAA:8 a=EUspDBNiAAAA:8 a=7CQSdrXTAAAA:8 a=z04GtWAkmwoQ-eLwQmwA:9 a=3ZKOabzyN94A:10 a=QEXdDO2ut3YA:10 a=2VI0MkxyNR6bbpdq8BZq:22 a=a-qgeE7W1pNrGK8U0ZQC:22 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwODMxMDA0NyBTYWx0ZWRfX5aDwbxx0LajM mbwLoj6e7QQ/tO0NXIgCOU7PNjs7qyozpUQjqDJ45LIyp2wh47ebrQSniDdoy1NkNTZyB54mDad LLtYlbESDtN29hYQ/l3lrx51fVtewzinyO13l3+1K/hC4stE/aoNS41mbi8YKpNNrM1FAdDcoE+ VmMp/tK7HICJBDqU7+m2n63pdGSL0kTYkkEFZBWlVEOGkrvXXNvsdFp7yh0N/25fpiwwXgYI47y oDWVgi25fSZRtUYT7hjMa/0M7HOH8o5YtBcE5U8RdOMVYHM0mrgN7Sp1ScEsp4W+Tye+ZtzIe4r Sn5jMG/cs7te6+xUNtGCqa506adP392vnusB5dVzyoBfjg1FuZBkp0IHEzbGpQ1WHLL1690B+KT g1MdguzYAAzMR2WRCy2OrbOO/P7H7/6DrfcrcZXP8y1s/t6xD2ZkNjp+J/fsIWo6Go7DgJH4ZJR uKgL7kXtBwdxYh3+k6w== X-Proofpoint-ORIG-GUID: EBSBb1hueli7MvlBNYYvrQBmViBRgGre X-Proofpoint-Spam-Info: AW1haW4tMjYwODMxMDA0NyBTYWx0ZWRfXx8EgjI0cg9we 1LCoFAmXVhwjjlbqbbSVeyQdHkgCNO7teC6xsYK62tfgzga5Fzcoyv3/2uU5L/B55ik/Uz91ajn IrZju1VH1GW/4afKH/lIY8a5ekKBEzc= X-Proofpoint-GUID: EBSBb1hueli7MvlBNYYvrQBmViBRgGre X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1176,Hydra:6.1.134,FMLib:17.12.100.49 definitions=2026-08-31_02,2026-08-27_02,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 phishscore=0 adultscore=0 clxscore=1015 priorityscore=1501 spamscore=0 suspectscore=0 malwarescore=0 bulkscore=0 lowpriorityscore=0 impostorscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2606150000 definitions=main-2608310047 On 8/26/2026 3:11 AM, Drew Fustini wrote: > On Tue, Aug 11, 2026 at 09:30:31PM +0800, Yin Li wrote: >> From: James Morse >> >> The MPAM driver identifies caches by id for use with resctrl. It >> needs to know the cache-id when probe-ing, but the value isn't set >> in cacheinfo until device_initcall(). Even after device_initcall(), >> the cache-id is only available if at least one CPU associated with >> the cache is online. >> >> Instead of making the driver wait, expose the code that generates the >> cache-id. The parts of the MPAM driver that run early can use this to >> set up the resctrl structures before cacheinfo is ready in >> device_initcall(). > > This patch would also be helpful for resctrl support on RISC-V, too. The > probe function in the CBQRI capacity allocation platform driver [1] has > the same problem. The current solution is to scan the online CPUs for a > cacheinfo leaf whose fw_token is the cache node from the phandle. > However, that does not work if no cpu sharing that cache is online yet. > Hi Drew, Thanks for the review. Good to know that cache_of_calculate_id() could help with the RISC-V CBQRI driver as well. Since the function is guarded by CONFIG_OF in cacheinfo.h, it should be available on DT-based RISC-V platforms without any issue. You're welcome to use it. > [..] >> +u32 cache_of_calculate_id(struct device_node *cache_node) >> { >> struct device_node *cpu; >> u32 min_id = ~0; >> @@ -238,15 +237,23 @@ static void cache_of_set_id(struct cacheinfo *this_leaf, >> id = arch_compact_of_hwid(id); >> if (FIELD_GET(GENMASK_ULL(63, 32), id)) { >> of_node_put(cpu); >> - return; >> + return ~0; > > Maybe this should be U32_MAX instead? > Regarding the ~0 vs U32_MAX point: You're right that U32_MAX is more appropriate than ~0 here. This is addressed in patch 06/15 ("arm_mpam: Fix cache ID sentinel from ~0UL to U32_MAX to match u32 return type"). https://lore.kernel.org/all/20260811-mpam-resctrl-dt-knp-support-v1-6-ea6397bead59@oss.qualcomm.com/ The fix is in a separate patch because this patch is based on James Morse's original unmerged work — I kept my fixes separate for easier review. The plan is to fold them back in once James has responded. > Thanks, > Drew > > [1] https://lore.kernel.org/all/20260729-dfustini-atl-sc-cbqri-dt-v6-8-7c22b05d461b@kernel.org/ -- Thx and BRs, Yin