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[78.88.45.245]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-b876b6865desm95154766b.12.2026.01.14.02.01.23 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 14 Jan 2026 02:01:23 -0800 (PST) Message-ID: <1be287ac-fce9-4f27-aa88-b1f786e968cd@oss.qualcomm.com> Date: Wed, 14 Jan 2026 11:01:21 +0100 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH RFC RFT] interconnect: qcom: implement get_bw with rpmh_read To: Georgi Djakov , Neil Armstrong Cc: linux-arm-msm@vger.kernel.org, linux-pm@vger.kernel.org, linux-kernel@vger.kernel.org, Bjorn Andersson References: <20251106-topic-sm8x50-icc-read-rpmh-v1-1-d03a2e5ca5f7@linaro.org> <8eb528dd-71fc-408e-a97c-d484198e4f81@kernel.org> Content-Language: en-US From: Konrad Dybcio In-Reply-To: <8eb528dd-71fc-408e-a97c-d484198e4f81@kernel.org> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Authority-Analysis: v=2.4 cv=aY5sXBot c=1 sm=1 tr=0 ts=69676975 cx=c_pps a=qKBjSQ1v91RyAK45QCPf5w==:117 a=FpWmc02/iXfjRdCD7H54yg==:17 a=IkcTkHD0fZMA:10 a=vUbySO9Y5rIA:10 a=s4-Qcg_JpJYA:10 a=VkNPw1HP01LnGYTKEx00:22 a=VwQbUJbxAAAA:8 a=EUspDBNiAAAA:8 a=pn0_eU-81vYunYMLtHMA:9 a=QEXdDO2ut3YA:10 a=NFOGd7dJGGMPyQGDc5-O:22 X-Proofpoint-ORIG-GUID: jNEbj_NPeFLbtnTJqSV8DKvVAaKDfRyZ X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwMTE0MDA4MiBTYWx0ZWRfXxmZW0zSHTL2/ y49C/hDdzBRFKtPzS3tuRO+xssNS3ZpLb6Mqp1HTkxY5CPi09AJsAhfefkxfYR6AyY39pVb+c9U NosEtLf77a/4KXNw4isZIcOziLwI89Y5WRuiCMK9dqd2PKCOBSP6KgVX83yYrYa15vSa6WIelxN LOeOO5ITF5bNo1+taaZdpbF/n9fwI7U4liBrYZVBq5FRbCGHa1QCYQ0DUkVaTstz03UlJM7k3K4 zhgSyUTmQ/fH1QoyMIW6KgjF6ftEWhB9Z1kYjhVX26NLBqTQxEqRCbnA4ertnJO7FWL0V8Bj7ti ztW6FuCpHRUW5cZTBSt1L3UPZdwGaSSnUh7UfFZyCZT2Z6JBj8DQMFSE1UO5+RMPQukfQ9XRkkT xxDkh8xZFU8YkZkEPA08WYQ+LTL7KCbZ4KnUcZTrp2dUeEiBxx747q5A7JHpwqQIBoKNQ9d9DuP QuzhwI9wbCX3M/hGjIg== X-Proofpoint-GUID: jNEbj_NPeFLbtnTJqSV8DKvVAaKDfRyZ X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1121,Hydra:6.1.9,FMLib:17.12.100.49 definitions=2026-01-14_03,2026-01-09_02,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 impostorscore=0 priorityscore=1501 suspectscore=0 malwarescore=0 bulkscore=0 lowpriorityscore=0 clxscore=1015 adultscore=0 phishscore=0 spamscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2512120000 definitions=main-2601140082 On 1/13/26 6:53 PM, Georgi Djakov wrote: > On 11/6/25 6:46 PM, Neil Armstrong wrote: >> Since we can actually read back the APPS rpmh interconnect >> BCM votes we can actually implement the get_bw() callback >> and provide a coherent average and peak bandwidth at probe time. >> >> The benefits of that are: >> - keep disabled BCMs disabled >> - avoid voting unused BCMs to INT_MAX >> >> If the interconnects are correctly described for a platform, >> all the required BCMs would be voted to the maximum bandwidth >> until sync_state is reached. >> >> Since we only get the BCM vote, we need to redistribute >> the vote values to the associated nodes. The initial BCM >> votes are read back at probe time in order to be ready when >> the get_bw() is called when a node is added. >> > > FWIW, I was able to finally test this on sdm845. Some nodes are indeed > showing reasonable bandwidth values instead of the default INT_MAX. As I learnt here https://lore.kernel.org/linux-arm-msm/1e7594dc-dca6-42e7-b478-b063e3325aff@oss.qualcomm.com/ rpmh_read() will only retrieve the currently active values, so as-is, this hunk: + /* For boot-up, fill the AMC vote in all buckets */ + for (i = 0; i < QCOM_ICC_NUM_BUCKETS; i++) { + bcm->vote_x[i] = x; + bcm->vote_y[i] = y; + } is lying about the state of wake/sleep buckets this is ""fine"" today, as I don't see any "if (old_bw == new_bw)" checks across the framework, but debugfs is going to report incorrect values and if anyone decides to add the aforementioned check, it may introduce issues where the values aren't commited to the hardware (because Linux is going to believe they're already set) Konrad