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Thu, 7 Mar 2024 08:21:47 +0000 (GMT) Received: from epsmgms1p2new.samsung.com (unknown [182.195.42.42]) by epsmtrp2.samsung.com (KnoxPortal) with ESMTP id 20240307082147epsmtrp29267d18e6dfbfebfd817c18c1fcf86ff~6bcZ_4IZt3066830668epsmtrp2D; Thu, 7 Mar 2024 08:21:47 +0000 (GMT) X-AuditID: b6c32a46-d61ff70000002596-d9-65e9791c7970 Received: from epsmtip2.samsung.com ( [182.195.34.31]) by epsmgms1p2new.samsung.com (Symantec Messaging Gateway) with SMTP id 71.9C.08817.B1979E56; Thu, 7 Mar 2024 17:21:47 +0900 (KST) Received: from KORCO156694 (unknown [10.229.18.72]) by epsmtip2.samsung.com (KnoxPortal) with ESMTPA id 20240307082147epsmtip2bd36f10a919d6306a599937faf190f41~6bcZuIhtv0640406404epsmtip2D; Thu, 7 Mar 2024 08:21:47 +0000 (GMT) From: =?utf-8?B?6rmA7J6s7JuQL0pBRVdPTiBLSU0=?= To: "'Tudor Ambarus'" , "'Sylwester Nawrocki'" , "'Chanwoo Choi'" , "'Alim Akhtar'" Cc: "'Sam Protsenko'" , "'Krzysztof Kozlowski'" , , , , "'linux-arm-kernel'" , "'Peter Griffin'" , =?utf-8?Q?'Andr=C3=A9_Draszik'?= , "'William McVicker'" , In-Reply-To: Subject: RE: samsung: clk: re-parent MUX to OSCCLK at run-time Date: Thu, 7 Mar 2024 17:21:47 +0900 Message-ID: <000001da7068$7f60f020$7e22d060$@samsung.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Mailer: Microsoft Outlook 16.0 Thread-Index: AQIrup01/zmT+XD05TC1AfQUk5ZcMgJSyW8WsHbDZHA= Content-Language: ko X-Brightmail-Tracker: H4sIAAAAAAAAA+NgFtrNJsWRmVeSWpSXmKPExsWy7bCmha5M5ctUg4X/hSwezNvGZrHl1WYW i+tfnrNa7NguYrH39VZ2i02Pr7FafOy5x2pxedccNosZ5/cxWWyY8Y/F4vCbdlaL531A7qdb cRarPv1ndODz2LZ7G6vHgk2lHneu7WHz2Lyk3qNvyypGj8+b5ALYorJtMlITU1KLFFLzkvNT MvPSbZW8g+Od403NDAx1DS0tzJUU8hJzU22VXHwCdN0yc4BOVVIoS8wpBQoFJBYXK+nb2RTl l5akKmTkF5fYKqUWpOQUmBfoFSfmFpfmpevlpZZYGRoYGJkCFSZkZ6xp3spU8Fi54uWcKcwN jH8Euxg5OSQETCSafv5nAbGFBHYwShy9o9TFyAVkf2KU+LHjIlTiG6PE/zM6MA1/LvUxQxTt ZZRYvm8HE4TzglGi98o2RpAqNgFPic0v7rGAJEQEdgFVHelmBXGYBc4yS7x8188OUsUpYCfR 9fASM4gtDGSvP/yLFcRmEVCRuDX1JBOIzStgKXHix2NmCFtQ4uTMJ2A3MQtoSyxb+JoZ4iYF iZ9Pl4H1ighYSXQf+84OUSMiMbuzDexWCYEzHBJfP9xmh2hwkVg87QUjhC0s8er4Fqi4lMTn d3vZIOx8ibYrZ6DiNRIbF1yCqreXWHTmJ1CcA2iBpsT6XfogpoSAssSRW1Cn8Ul0HP7LDhHm lehoE4JoVJO4P/Uc1HAZiUlHVjJNYFSaheSxWUgem4XkgVkIuxYwsqxiFEstKM5NTy02KjCC R3Zyfu4mRnAq1nLbwTjl7Qe9Q4xMHIyHGCU4mJVEeFksXqYK8aYkVlalFuXHF5XmpBYfYjQF BvVEZinR5HxgNsgriTc0sTQwMTMzNDcyNTBXEue91zo3RUggPbEkNTs1tSC1CKaPiYNTqoFp Z17wgt703wsSjMN85XbKMx5p9Lv8REqmj11vV/MWI74PO86v9Vh9dkeW5fOfd+bYMzv98JMV nTLt3+Inkjf1nk2bI3fvVmWL3jclI6cdNy2c1aa+UDk6/Y9ytl/4+ZcJZ1pZfJ8+rdxp3d7k yXp0itbWDTqz7hleXuhmef2jMIdl3Ze4S+tMGUy+7F72eLXHcfnegxH9Zboad9/pFAcwe4py 6xr2l3kFKXqt38g34Wzhgw0e/XzvZJYuzTv3SMD99bpaIX4l2TA+wyStv9cPTI06yFzzsOHR 4/6Zd95wm86epDD9ObPYtz4DhwYG59Qly2arBVeEzffgmvWiQ6KJaUVXZfjWuMSv5g7XYpmV WIozEg21mIuKEwFAkzzqTgQAAA== X-Brightmail-Tracker: H4sIAAAAAAAAA+NgFlrJIsWRmVeSWpSXmKPExsWy7bCSvK505ctUg7XvtC0ezNvGZrHl1WYW i+tfnrNa7NguYrH39VZ2i02Pr7FafOy5x2pxedccNosZ5/cxWWyY8Y/F4vCbdlaL531A7qdb cRarPv1ndODz2LZ7G6vHgk2lHneu7WHz2Lyk3qNvyypGj8+b5ALYorhsUlJzMstSi/TtErgy /q9sZy7YpVRxY28nSwPjQYEuRk4OCQETiT+X+phBbCGB3YwSm94bQMRlJJY/62ODsIUl7rcc Ye1i5AKqecYocenePSaQBJuAp8TmF/dYQBIiAnsYJS7f+MEG4jALXGaWaL2xjgmipZ9R4u7v w2A7OAXsJLoeXgKzhYHs9Yd/sYLYLAIqEremngQbyytgKXHix2NmCFtQ4uTMJywgNrOAtsTT m0/h7GULXzND3Kcg8fPpMrA5IgJWEt3HvrND1IhIzO5sY57AKDwLyahZSEbNQjJqFpKWBYws qxglUwuKc9Nziw0LjPJSy/WKE3OLS/PS9ZLzczcxgmNTS2sH455VH/QOMTJxMB5ilOBgVhLh ZbF4mSrEm5JYWZValB9fVJqTWnyIUZqDRUmc99vr3hQhgfTEktTs1NSC1CKYLBMHp1QD04Y8 C7/7FyYtfLInnG/NvHWhb6dvVNvJUmNd8HRjQb2244SFMjND/tyfumPfjyiPI+lrQkO/5q3b FMX9X0I47bfkHyajadcOCfquT/GXSZsov+W9aAdX9O0G6wXXt885xCV/QWGd+IkPJQZnHl7k 3DNvQsDBKXsDb5ffzpCOvtfxaX9PHAPbL4sFzPmhNz3nCpsc+rtnu8nXGTxvJyxZ/WAyx5/z K2/ZP1zpNsk84rDMxBz3lffPZT97a24uf2n+3lvxldce1fCLBjF3i9bJi31478064ezBt4eu XN1c4frCULZ+Vpjdk40H4kR/nNibHJO448aFgNOd5UvUJu88a/XZzWPR7UmzzWMeTc5Pcpje q8RSnJFoqMVcVJwIAB+qjW88AwAA X-CMS-MailID: 20240307082147epcas2p440fe042df70c6001d91f9dbe5090f3ef X-Msg-Generator: CA Content-Type: text/plain; charset="utf-8" X-Sendblock-Type: AUTO_CONFIDENTIAL CMS-TYPE: 102P DLP-Filter: Pass X-CFilter-Loop: Reflected X-CMS-RootMailID: 20240306032022epcas2p14368c055af804c2f066a6b1ec5cee070 References: Hi Tudor On 3/6/24 12:20, Tudor Ambarus wrote: >=20 > Hi, >=20 > Trying to get some feedback from the samsung experts. Please consider the > following: >=20 > --------------------------------------------- > =7C CMU_PERIC0 = =7C > =7C = =7C > =7C MUX_USI = =7C > =7C = =7C > =7C =7C=5C = =7C > OSCCLK ---=7C->=7C =5C = =7C > =7C =7C =5C = =7C > =7C =7C M =7C = =7C > =7C =7C U =7C--> DIV_CLK_PERIC0_USI*_ --> GATE_U= SI =7C > =7C =7C X =7C (1 =7E 16) = =7C > =7C =7C / = =7C > DIV_CLKCMU_PERIC0_IP ---=7C->=7C / = =7C > (1 =7E 16) =7C =7C =7C/ = =7C > =7C =7C = =7C > =7C =7C = =7C > =7C =7C MUX_I3C = =7C > =7C =7C = =7C > =7C =7C =7C=5C = =7C > --=7C->=7C =5C = =7C > =7C =7C =5C = =7C > =7C =7C M =7C = =7C > =7C =7C U =7C--> DIV_CLK_PERIC0_I3C --> GATE_I3C= =7C > =7C =7C X =7C = =7C > =7C =7C / = =7C > OSCCLK ---=7C->=7C / = =7C > =7C =7C/ = =7C > =7C = =7C > --------------------------------------------- >=20 > Is it fine to re-parent the MUX_USI from above to OSCCLK at run-time, > during normal operation mode? Experimentally I determined that it's fine, > but the datasheet that I'm reading mentions OSCCLK just in the low-power > mode context: > i/ CMU ... =22Communicates with Power Management Unit (PMU) to stop clock= s > or switch OSC clock before entering a Low-Power mode to reduce power > consumption by minimizing clock toggling=22. > ii/ =22All CMUs have MUXs to change the OSCCLK during power-down mode=22. >=20 > Re-parenting the MUX to OSCCLK allows lower clock rates for the USI block= s > than the DIV_CLK_PERIC0_USI can offer. For a USI clock rate below > 6.25 MHz I have to either reparent MUX_USI to OSCCLK, or to propagate the > clock rate to the common divider DIV_CLKCMU_PERIC0_IP. I find the > propagation to the common DIV less desirable as a low USI clock rate > affects I3C by lowering its clock rate too. Worse, if the common bus > divider is not protected (using CLK_SET_RATE_GATE), USI can lower the I3C > clock rate without I3C noticing. >=20 > Either re-parenting the MUX_USI to OSCCLK, or propagating the clock rate > to DIV_CLKCMU_PERIC0_IP allows the same clock ranges. The first with the > benefit of not affecting the clock rate of I3C for USI clock rates below > 6.25 MHz. Is it fine to re-parent MUX_USI to OSCCLK at run-time? >=20 > If no feedback is received I lean towards propagating the USI clock rate > to the common divider, but by protecting it with CLK_SET_RATE_GATE. >=20 > Feel free to add in To: or Cc: whoever might be interested. Thanks, ta =22DIV_CLK_PERIC0_USI=22 re-parent to OSCCLK is already used samsung downst= ream driver. Looking at the samsung downstream SPI driver, if the SPI request clock is l= ower than the clock that can be supported by the CMU, it re-parents to OSCC= LK. There is no problem with clock switching before USI data transfer. Thanks Jaewon Kim