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Wed, 25 Jun 2025 00:46:03 -0700 (PDT) Received: from localhost ([2a01:e0a:3c5:5fb1:87a0:eae0:c854:b578]) by smtp.gmail.com with UTF8SMTPSA id 5b1f17b1804b1-45380fd167bsm14015175e9.0.2025.06.25.00.46.03 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 25 Jun 2025 00:46:03 -0700 (PDT) From: Jerome Brunet To: Jian Hu Cc: Xianwei Zhao , Chuan Liu , Neil Armstrong , Kevin Hilman , Stephen Boyd , Michael Turquette , Dmitry Rokosov , robh+dt , Rob Herring , devicetree , linux-clk , linux-amlogic , linux-kernel , linux-arm-kernel Subject: Re: [PATCH v3 4/6] clk: meson: t7: add support for the T7 SoC PLL clock In-Reply-To: <22a24fe6-9e62-4aba-825e-aee214f683ee@amlogic.com> (Jian Hu's message of "Wed, 25 Jun 2025 10:52:28 +0800") References: <20250509074825.1933254-1-jian.hu@amlogic.com> <20250509074825.1933254-5-jian.hu@amlogic.com> <1jtt5ny6gq.fsf@starbuckisacylon.baylibre.com> <4dd25114-212d-44d6-938a-63871750c292@amlogic.com> <1jh60fd52u.fsf@starbuckisacylon.baylibre.com> <22a24fe6-9e62-4aba-825e-aee214f683ee@amlogic.com> User-Agent: mu4e 1.12.9; emacs 30.1 Date: Wed, 25 Jun 2025 09:46:02 +0200 Message-ID: <1j7c10jmbp.fsf@starbuckisacylon.baylibre.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20250625_004606_501906_7E826601 X-CRM114-Status: GOOD ( 17.68 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Wed 25 Jun 2025 at 10:52, Jian Hu wrote: > On 2025/6/17 0:27, Jerome Brunet wrote: >> [ EXTERNAL EMAIL ] >> >> On Thu 12 Jun 2025 at 21:02, Jian Hu wrote: >> >>>>> + >>>>> +static struct clk_regmap t7_pcie_pll_od =3D { >>>>> + .data =3D &(struct clk_regmap_div_data){ >>>>> + .offset =3D ANACTRL_PCIEPLL_CTRL0, >>>>> + .shift =3D 16, >>>>> + .width =3D 5, >>>>> + .flags =3D CLK_DIVIDER_ONE_BASED | >>>>> + CLK_DIVIDER_ALLOW_ZERO, >>>> What's the behaviour of the divider on zero then ? >>> >>> If there is no CLK_DIVDER_ALLOW_ZERO, there is a warning when registeri= ng >>> t7_pcie_pll_od. >>> >>> like this: >>> >>> ------------[ cut here ]------------ >>> WARNING: CPU: 1 PID: 1 at drivers/clk/clk-divider.c:140 >>> divider_recalc_rate+0xfc/0x100 >>> pcie_pll_od: Zero divisor and CLK_DIVIDER_ALLOW_ZERO not set >>> Modules linked in: >>> CPU: 1 PID: 1 Comm: swapper/0 Not tainted >>> 5.4.283-09976-ga803e94eed88-dirty #91 >>> Hardware name: tm2_t962e2_ab311 (DT) >>> Call trace: >>> [ffffffc020003750+ 64][] dump_backtrace+0x0/0x1e4 >>> [ffffffc020003790+ 32][] show_stack+0x24/0x34 >>> [ffffffc0200037b0+ 96][] dump_stack+0xbc/0x108 >>> [ffffffc020003810+ 144][] __warn+0xf4/0x1b8 >>> [ffffffc0200038a0+ 64][] warn_slowpath_fmt+0xac/0= xc8 >>> [ffffffc0200038e0+ 64][] divider_recalc_rate+0xfc/= 0x100 >>> [ffffffc020003920+ 80][] >>> clk_regmap_div_recalc_rate+0x74/0x88 >>> [ffffffc020003970+ 96][] __clk_register+0x62c/0xb= 78 >>> >>> so add it to avoid the warning. >> That does not really answer my question > > > Sorry, I did not get you before. > > I have set OD to 0.=C2=A0 And measure pcie frequency,=C2=A0 It is 37.5Mhz. > > 4800Mhz/2/32/2=3D37.5Mhz, and the OD equal zero means divided by 32 in fa= ct. > CLK_DIVIDER_MAX_AT_ZERO maybe ? > Here is the test result: > > devm 0xfe008140 32 > > 0xD40C04C8 > > cat /sys/kernel/debug/meson-clk-msr/measure_summary | grep pcie > > [16] pcie_clk_inp =C2=A0=C2=A0=C2=A0=C2=A0 37500000=C2=A0 +/1 3125HZ > > > the OD divider is N crossover. it is one based. > > and It's possible to go from 1 to 31 crossovers. --=20 Jerome