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[103.229.16.4]) by smtp.gmail.com with ESMTPSA id 41be03b00d2f7-cc15523b579sm1412666a12.3.2026.08.19.22.39.55 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 19 Aug 2026 22:39:58 -0700 (PDT) Message-ID: <181944c2-2484-4384-9c91-45cc87f31955@oss.qualcomm.com> Date: Thu, 20 Aug 2026 13:39:52 +0800 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] clk: qcom: ipq-cmn-pll: keep the CMN block bus clocks enabled To: Konrad Dybcio , Stanislaw Pal Cc: Bjorn Andersson , Stephen Boyd , Michael Turquette , Mieczyslaw Nalewaj , Brian Masney , linux-arm-msm@vger.kernel.org, linux-clk@vger.kernel.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org References: <20260730191353.557494-1-kuncy7@gmail.com> <20260803091003.15285-1-kuncy7@gmail.com> <8af46926-fecc-4396-973e-2290ae285998@oss.qualcomm.com> Content-Language: en-US From: Jie Luo In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwODIwMDAzOSBTYWx0ZWRfX5mLFkWEN7nLH ca1vxPSJIKqgLeAn43D4aszSoohD4Zd6p8uu50QGOUJun/BNpRc7Wr3/PAb1OecfT08ycz6X+21 yIHFxIZe2tdchooSzXOwaGe5zYjtAzCNVw4+VrcIXL62Pm2Qg/BsuH80GlWlclF26aj2G+rQIUk /YTfixEv8t9UqS3ufNCVXTUrppEDb7lGZC0g1yiRnCGI97WGaRvALKVqm2Hi9aQ6wnUBUQwpMXw rld38cUwkrcZak1sqZXGQJrd+HaW5Dw+JQ40K3TBYQf7YMjGnTlKO5iInrfMShWdm/+8nke0Ucq BOnM+y32n8qnmNommk2U1cKJRbGunBxxKpoQIKU8wrYY2FqqyVkeVwCGIKZaGe5pDIeJIWBmpo5 nRhKtU7OT0w363vIO/XvR9PZV9ySnIYQ2jTP9bhSknHrFb16W4CZIh5zxtX3KGFNFr2Z96wJYW+ wV7Sewl2amBVroDx3Wg== X-Authority-Analysis: v=2.4 cv=cuOrVV4i c=1 sm=1 tr=0 ts=6a86932f cx=c_pps a=Qgeoaf8Lrialg5Z894R3/Q==:117 a=nuhDOHQX5FNHPW3J6Bj6AA==:17 a=IkcTkHD0fZMA:10 a=Sv0fKeRqtYgA:10 a=s4-Qcg_JpJYA:10 a=VkNPw1HP01LnGYTKEx00:22 a=u7WPNUs3qKkmUXheDGA7:22 a=YMgV9FUhrdKAYTUUvYB2:22 a=BrIDYzEHq6298WO724AA:9 a=3ZKOabzyN94A:10 a=QEXdDO2ut3YA:10 a=x9snwWr2DeNwDh03kgHS:22 X-Proofpoint-ORIG-GUID: KqkP-e55qmpKwMmdjFnqxq23u8D9cGJO X-Proofpoint-GUID: KqkP-e55qmpKwMmdjFnqxq23u8D9cGJO X-Proofpoint-Spam-Info: AW1haW4tMjYwODIwMDAzOSBTYWx0ZWRfX/1UpDD3SsGRC nAvvODiAZD6+UPu6xnNxUPhyiKBTKhiU623AW8y8Ke2axw5BA34Vhm7Dyfe5OZJUqDhALxx2w0e OCkA9eERi9wSP8zE9ziuvm+pq1/UVmY= 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=2026-08-19_06,2026-08-19_02,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 impostorscore=0 malwarescore=0 suspectscore=0 phishscore=0 clxscore=1015 lowpriorityscore=0 adultscore=0 spamscore=0 bulkscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2606150000 definitions=main-2608200039 On 8/19/2026 9:00 PM, Konrad Dybcio wrote: > On 8/4/26 1:03 PM, Jie Luo wrote: >> >> >> On 8/3/2026 5:10 PM, Stanislaw Pal wrote: >>>> The CMN PLL AHB/SYS clocks will remain enabled as long as a downstream >>>> consumer of the CMN PLL clocks is active — this behaviour was confirmed >>>> experimentally on the IPQ9574 platform as example. >>> That is exactly the mechanism - and it is exactly what IPQ5018 does not >>> have. On IPQ9574 the nsscc node consumes the CMN PLL outputs in DT: >>> >>> ipq9574.dtsi: >>> nsscc: clock-controller@39b00000 { >>> clocks = <&xo_board_clk>, >>> <&cmn_pll NSS_1200MHZ_CLK>, >>> <&cmn_pll PPE_353MHZ_CLK>, ... >>> >>> so the device link holds the supplier active, which is what your >>> insmod/devmem experiment shows. >>> >>> On IPQ5018 there is no such consumer: nothing in ipq5018.dtsi references >>> any cmn_pll output clock - the only occurrences of the phandle are the >>> provider node itself and its own assigned-clocks. The actual users of >>> the CMN outputs on this SoC (the internal GE PHY and the uniphy blocks) >>> take them directly in hardware, with no DT linkage, so no device link >>> ever holds the provider active. A few ms after probe the autosuspend >>> gates the AHB/SYS clocks, and the box dies on the next bus access - >>> which is the measured behaviour the patch description quotes. >> >> The CMN PLL output clocks do not depend on the AHB or SYS clocks. They >> continue to operate correctly at the fixed rates even when the AHB >> and SYS clocks are disabled. Therefore, once the CMN PLL module is >> loaded, its output clocks are expected to operate at the correct >> frequencies. > > Linux sees there's no consumers for the clocks the CMN PLL provides > and gates them, subsequently also gating the PLL itself as all of > its children become offline. > > I can't find the docs that would show me what IPs consume this block, > could you please help out here Jie? > On IPQ5018, the CMN PLL provides a 50 MHz output clock that is used as the reference clock for the connected Ethernet device. > Konrad