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[83.233.6.197]) by smtp.gmail.com with ESMTPSA id 38308e7fff4ca-387068923aasm13048961fa.3.2026.02.13.08.05.21 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 13 Feb 2026 08:05:21 -0800 (PST) Date: Fri, 13 Feb 2026 17:05:19 +0100 From: Marcus Folkesson To: Peter Rosin Cc: Wolfram Sang , Michael Hennerich , Bartosz Golaszewski , Andi Shyti , Bartosz Golaszewski , linux-i2c@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org Subject: Re: [PATCH v5 2/5] i2c: mux: add support for per channel bus frequency Message-ID: References: <20260213-i2c-mux-v5-0-fb2cbf9979b3@gmail.com> <20260213-i2c-mux-v5-2-fb2cbf9979b3@gmail.com> Precedence: bulk X-Mailing-List: linux-i2c@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha512; protocol="application/pgp-signature"; boundary="6fcNXqbn+kKd91zT" Content-Disposition: inline In-Reply-To: --6fcNXqbn+kKd91zT Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable Hi Peter! On Fri, Feb 13, 2026 at 12:48:13PM +0100, Peter Rosin wrote: > Hi! >=20 [...] > > + if (priv->adap.clock_hz && priv->adap.clock_hz !=3D parent->clock_hz)= { > > + mux_locked_ancestor =3D i2c_mux_topmost_mux_locked(adap); > > + root =3D i2c_root_adapter(&adap->dev); > > + > > + /* > > + * If there's a mux-locked mux in our ancestry, lock the parent > > + * of the topmost one. Mux-locked muxes don't propagate locking > > + * to their parents, so we must explicitly acquire the lock above > > + * the highest mux-locked ancestor to reach the root adapter. > > + */ >=20 > As may be more apparent from my recent v4 response(?), this is not > what you want. You want mux_locked_ancestor to be the nearest > mux-locked ancestor. Hrm, I think we are pointing at the same thing but naming it differently; M= 1 in this chain: Root - P1 - M1 - M2 - P2 - D1 I'm thinking 'topmost' means the one closest to the root (ancestor most far away), but I don't stick to that naming and I am happy to change it. >=20 >=20 > > + if (mux_locked_ancestor) > > + i2c_lock_bus(mux_locked_ancestor->parent, I2C_LOCK_ROOT_ADAPTER); > > + > > + ret =3D i2c_adapter_set_clk_freq(root, priv->adap.clock_hz); > > + > > + if (mux_locked_ancestor) > > + i2c_unlock_bus(mux_locked_ancestor->parent, I2C_LOCK_ROOT_ADAPTER); > > + > > + if (ret < 0) { > > + dev_err(&adap->dev, > > + "Failed to set clock frequency %dHz on root adapter %s: %d\n", > > + priv->adap.clock_hz, root->name, ret); > > + > > + return ret; > > + } > > + } > > + >=20 > Here, you set the frequency /before/ ->select. >=20 > > + return muxc->select(muxc, priv->chan_id); > > +} > > + > > +static void i2c_mux_deselect_chan(struct i2c_adapter *adap, u32 chan_i= d) > > +{ > > + struct i2c_mux_priv *priv =3D adap->algo_data; > > + struct i2c_mux_core *muxc =3D priv->muxc; > > + struct i2c_adapter *parent =3D muxc->parent; > > + struct i2c_mux_core *mux_locked_ancestor =3D NULL; > > + struct i2c_adapter *root; > > + int ret; >=20 > And here, you restore the frequency, but /before/ ->deselect. >=20 > Thers's no symmetry in that... Good point, I will change that. >=20 > Cheers, > Peter Best regards, Marcus Folkesson --6fcNXqbn+kKd91zT Content-Type: application/pgp-signature; name=signature.asc -----BEGIN PGP SIGNATURE----- iQIzBAEBCgAdFiEEBVGi6LZstU1kwSxliIBOb1ldUjIFAmmPS7sACgkQiIBOb1ld UjJCaA//X2a3lgD8Yp6cOmM9sQs3eZosPkXjeUxzy15UbQSZrNOGnU3D/Ujz2CSQ QMwdD+KJKws3jTcawHXesvP8P5zePLAo+/Gj78jqJb9QWK6zEdTi4mJLKBDdaSG8 L9UzSJF17NuHfolZ/nAVo3s84jooY4ZE3PU22FPoJzmwtRU28pyl7JKUQLTz8UT8 25AtgTtO8OfYrYiNXcNilZ2ZqwEgamhE9q8U6GKjErrsDJFG97Pal795bis3fUVu JChwmQ/HT2NZhK/aXBGxqVqEYIirQL/0MC7ZbN4wnEtK2MqNXkwKK5if2Or6pKbE tP4Ijg5OXrtQsqUhsRbmfxH3Jb5MJsgvmxbde8NPAi0s4nc4IAicL2Ld1ZyaHSXF pZ0LiekLFCN+BJH3adCaPWUmu6hIxK9oLqXkNTxtZVXEai2ealPBeq1v1F1QfBkx XrJhb6NRFI82H20vZnAXJyN5z80fVeJHhv527zNwfFpvUIr5itDfB9uDBprDNFiI jpqwdxILKG4eP6OglarXcBWrVLMrqx+1YsEhTQUOvSMlqa+P6JIDFDhYxR9B+sdM lser0vwQyOBt3mrLkyJJCC/HDjZcdbZ2Q0WRRjiSyUlWoiaRD7wPNXpBHZLfyAqW KdOHkIJOJa0QgDJ00I9RfuzhHi5Zv2JtHnzoOBNkpagfCbbh8hY= =AYL/ -----END PGP SIGNATURE----- --6fcNXqbn+kKd91zT--