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Wed, 21 Oct 2026 09:13:38 -0700 (PDT) Received: from [192.168.1.10] ([122.164.81.208]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-8a0895e273bsm1131642b3a.41.2026.10.21.09.13.33 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 21 Oct 2026 09:13:37 -0700 (PDT) Message-ID: <4dff1a97-8c44-449c-86a5-5eac047ab909@oss.qualcomm.com> Date: Wed, 21 Oct 2026 21:43:30 +0530 X-Mailing-List: devicetree@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 1/4] interconnect: icc-clk: support N:1 master-to-slave topology To: Konrad Dybcio , Georgi Djakov , Bjorn Andersson , Abel Vesa , Stephen Boyd , Brian Masney , Jerome Brunet , Rob Herring , Krzysztof Kozlowski , Conor Dooley Cc: linux-pm@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arm-msm@vger.kernel.org, linux-clk@vger.kernel.org, devicetree@vger.kernel.org References: <20261007-ipq9650_apss_clk-v1-0-fd4c2b3cbdea@oss.qualcomm.com> <20261007-ipq9650_apss_clk-v1-1-fd4c2b3cbdea@oss.qualcomm.com> <21a95133-eba9-4655-95b4-9aa947c081f9@oss.qualcomm.com> Content-Language: en-US From: Kathiravan Thirumoorthy In-Reply-To: <21a95133-eba9-4655-95b4-9aa947c081f9@oss.qualcomm.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Authority-Analysis: v=2.4 cv=aI5lOr9m c=1 sm=1 tr=0 ts=6ad8e4b4 cx=c_pps a=rEQLjTOiSrHUhVqRoksmgQ==:117 a=rZLzW5DhxuwyX7/NBrPT8g==:17 a=IkcTkHD0fZMA:10 a=660iZSQnnn4A:10 a=s4-Qcg_JpJYA:10 a=VkNPw1HP01LnGYTKEx00:22 a=u7WPNUs3qKkmUXheDGA7:22 a=gowsoOTTUOVcmtlkKump:22 a=L14mbm2-ywthVrTR10cA:9 a=3ZKOabzyN94A:10 a=QEXdDO2ut3YA:10 a=2VI0MkxyNR6bbpdq8BZq:22 X-Proofpoint-ORIG-GUID: 0zrzO5v3ZiAY3QexLNXlNhx-GKdcUytP X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYxMDIxMDA2NCBTYWx0ZWRfX+oPnpTyLHXMy NY8WrFjqHnUqtrYY4KKYM1cSMEOYxDo+kT9jsOxXWnuIRVLzPdfNoZT2RQymXbEm4z3oxBG8Z+V KN46huHCMHC+gwOr8s33WY3OHKG3/fdViq35VDL0AW1t6VS00qh98hrRbiVn92CIIaQ/TJ51H4j uqAkWjFrFFCzWOvlu09u6yLKYlqzp5CrB/i7USLVdEpYKNp4umRSQmW3iAGkFS9WjWUo8au4z3+ t7MTE1GQQZyn5dYgXrCP0SdMglAV5qP/5pupf3x22m1GVjj0qdrEYieJwhGsWrwMTcjKIDJYyqX HxgQHx0z5aMrbEqvEZ+iHTt+q/j2kDVfU/1NCwCqnB3Ria0+k6mqXa+hTUGftoBV23iiTsKNGpU 2GgB1z64sHVNeDCfu8x0NiMP9pdA1tGNWXanPpeFS4eT5PtXhcyQfxfxYhgDnRtyX7v8gWxry3H 5G6sZqRIz4T+osCFqaA== X-Proofpoint-GUID: 0zrzO5v3ZiAY3QexLNXlNhx-GKdcUytP X-Proofpoint-Spam-Info: AW1haW4tMjYxMDIxMDA2NCBTYWx0ZWRfXzaTIdBFOdqQT 0JnaukmpyWS8uRxtWPNQLTLK3CfjuibbZlOQvo7RXZSQD/hVFdRD+PYUmtIt6K1u4csW6fYnMDw 0bIzKRm2dIIFpGmzq3st89iDuQfZNjo= X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1176,Hydra:6.1.138,FMLib:17.12.100.49 definitions=2026-10-21_04,2026-10-21_02,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 clxscore=1015 impostorscore=0 spamscore=0 bulkscore=0 malwarescore=0 suspectscore=0 adultscore=0 phishscore=0 lowpriorityscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2610190000 definitions=main-2610210064 On 10/16/2026 7:42 PM, Konrad Dybcio wrote: > On 10/7/26 8:50 AM, Kathiravan Thirumoorthy wrote: >> icc_clk_register() assumes each icc_clk_data entry describes a unique >> master/slave pair and creates both nodes for every entry. When several >> masters share the same slave_id, the shared slave node is created and >> added again on each later entry. icc_node_create() returns the existing >> node, so icc_node_add() hits WARN_ON(node->provider): > [...] > >> - return clk_set_rate(qn->clk, icc_units_to_bps(src->peak_bw)); >> + /* >> + * Multiple master nodes can share the same underlying clock (N:1 >> + * topology, e.g. several CPU clusters voting on one L3 clock). >> + * Aggregate the peak bandwidth across all of them before setting >> + * the rate, otherwise the last caller wins and can undervote what >> + * another master already asked for. >> + */ >> + list_for_each_entry(node, &provider->nodes, node_list) { >> + struct icc_clk_node *n = node->data; >> + >> + if (n && clk_is_match(n->clk, qn->clk)) >> + rate = max(rate, icc_units_to_bps(node->peak_bw)); >> + } > GPT has the following concern: > > [P2] Recompute the shared clock rate when a master drops its vote > drivers/interconnect/icc-clk.c:36-42 > > The zero-bandwidth path returns before the new shared-clock aggregation. > If one master had set the shared clock to a high rate and then drops its > vote while another master still votes, the clock remains at the old, > higher rate: the remaining master’s icc_clk_set() is not necessarily > called. Recompute the maximum vote from all nodes sharing the clock on > this path, and apply that rate when other masters still have votes. Let me review this and get back. > > Konrad