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Sverdlin" , Dong Aisheng , Shawn Guo , Sascha Hauer , Pengutronix Kernel Team , Fabio Estevam , linux-i2c@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v3] i2c: lpi2c: cache peripheral clock rate Date: Tue, 02 May 2023 08:50:06 +0200 Message-ID: <2143344.irdbgypaU6@steina-w> Organization: TQ-Systems GmbH In-Reply-To: References: <20230310130815.562418-1-alexander.sverdlin@siemens.com> <4797405.GXAFRqVoOG@steina-w> MIME-Version: 1.0 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20230501_235009_589099_A0D6924C X-CRM114-Status: GOOD ( 14.35 ) 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: , Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org Hello Wolfgang, Am Sonntag, 30. April 2023, 09:05:55 CEST schrieb Wolfram Sang: > * PGP Signed by an unknown key > = > > > IIRC this is a general problem^w limitation of the clock framework, > > > clock providers cannot use clocks themselves in certain callback, e.g. > > > set_rate. > > = > > Well, that's essentially impossible when this clock provider is attached > > via i2c. i2c transfers potentially need to change or prepare clocks. > = > So, as I get it, this is not a specific lpi2c problem but affecting any > I2C controller driver which uses get_rate() to setup a transfer to a > remote I2C clock provider? And this lockdep warning is a false-positive? Yes, IMHO this could potentially occur on every I2C controller driver, if a = clock provider while holding the clk_prepare_lock, e.g. during registration= , = issues an i2c transfer. I'm not so sure if this is a false-positive, but more like trying to do a = nested lock. Best regards Alexander -- = TQ-Systems GmbH | M=FChlstra=DFe 2, Gut Delling | 82229 Seefeld, Germany Amtsgericht M=FCnchen, HRB 105018 Gesch=E4ftsf=FChrer: Detlef Schneider, R=FCdiger Stahl, Stefan Schneider http://www.tq-group.com/ _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel