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<20260508131830.GA1135235-robh@kernel.org> <007a01dcdef9$05ba7140$112f53c0$@gmx.de> In-Reply-To: Subject: AW: AW: [PATCH 1/2] dt-bindings: i2c: Add i2c-shared-gpio Date: Sat, 9 May 2026 22:41:48 +0200 Message-ID: <00ef01dcdff4$42318c70$c694a550$@gmx.de> Precedence: bulk X-Mailing-List: linux-i2c@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable X-Mailer: Microsoft Outlook 16.0 Thread-Index: AQIKgUW0k0IN4HI9csbwIs8kp6Kp3wLKDayEAPY4WTACKFuNHgJo4OeptWhXnFA= Content-Language: de X-Provags-ID: V03:K1:pVzEqyV2sM5VJJgX9QTq2pS488ZY/JAAkZ6Ztm9e/ncXrnxiMro 591hhN/bhcfE1FT7S70ufQi9psenKayYRp18Baf1dTdKv0F4o9moFdlB3Un6yXw6mNqPKC2 0Xg0a8H9ApKtocQN1MCej7FMoSK0Ko3yTDnAEEBf2IJOjKncyeMkSOZmunFgCINZQzoPv9N ON4wvM4hmFZhNq3V9MLyw== X-Spam-Flag: NO UI-OutboundReport: notjunk:1;M01:P0:O2pd3BMMync=;W4e020ALV+IUmem7Baj+QLjBPEI 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Mai 2026 19:39 > An: markus.stockhausen@gmx.de; Bartosz Golaszewski > Cc: 'Rob Herring' ; andi.shyti@kernel.org; linux-i2c@vger.kernel.org > Betreff: Re: AW: [PATCH 1/2] dt-bindings: i2c: Add i2c-shared-gpio >... > > Now, the GPIO subsystem since recently allows for shared GPIOs[1]. This > sounds like the proper approach to me. Sadly, I can't help much because > I have not used this API so far. So, it seems you rather need a GPIO > expert... CCing Bart. > > @Bart: is it possible to share a GPIO so that multiple i2c-gpio > instances can use the same GPIO as SCL? Use case is explained in the > cover letter[2]. Thanks fort he hint. That looks partly promising. I gave this a quick try= =20 on Kernel 6.18 in OpenWrt. Set the target to HAVE_SHARED_GPIOS.=20 Finally added several backports (deadlock stalled the boot). Now it at=20 least starts. This dts: i2c0: i2c-sfp0 { compatible =3D "i2c-gpio"; #address-cells =3D <1>; #size-cells =3D <0>; scl-gpios =3D <&gpio1 31 (GPIO_ACTIVE_HIGH | GPIO_OPEN_DRAIN)>; sda-gpios =3D <&gpio1 6 (GPIO_ACTIVE_HIGH | GPIO_OPEN_DRAI= N)>; }; i2c1: i2c-sfp1 { compatible =3D "i2c-gpio"; #address-cells =3D <1>; #size-cells =3D <0>; scl-gpios =3D <&gpio1 31 (GPIO_ACTIVE_HIGH | GPIO_OPEN_DRAIN)>; sda-gpios =3D <&gpio1 7 (GPIO_ACTIVE_HIGH | GPIO_OPEN_DRAI= N)>; }; Gives these messages: [ 2.048352] i2c-gpio i2c-sfp0: Slow GPIO pins might wreak havoc into I2C/SMBus bus timing [ 2.058333] i2c-gpio i2c-sfp0: using lines 542 (SDA) and 573 (SCL) [ 2.066139] i2c-gpio i2c-sfp1: Slow GPIO pins might wreak havoc into I2C/SMBus bus timing [ 2.076333] i2c-gpio i2c-sfp1: using lines 543 (SDA) and 574 (SCL) [ 2.084817] sfp sfp-p9: Host maximum power 1.0W [ 2.091419] sfp sfp-p10: Host maximum power 1.0W [ 2.200954] In rtldsa_vlan_setup [ 2.397223] gpio-574 (scl): gpio_set_open_drain_value_commit: Error in set_value for open drain err -1 [ 2.407907] gpio-574 (scl): gpio_set_open_drain_value_commit: Error in set_value for open drain err -1 [ 2.418605] gpio-574 (scl): gpio_set_open_drain_value_commit: Error in set_value for open drain err -1 [ 2.429275] gpio-574 (scl): gpio_set_open_drain_value_commit: Error in set_value for open drain err -1 [ 2.439937] gpio-574 (scl): gpio_set_open_drain_value_commit: Error in set_value for open drain err -1 [ 2.450584] gpio-574 (scl): gpio_set_open_drain_value_commit: Error in set_value for open drain err -1 [ 2.461223] gpio-574 (scl): gpio_set_open_drain_value_commit: Error in set_value for open drain err -1 [ 2.471875] gpio-574 (scl): gpio_set_open_drain_value_commit: Error in set_value for open drain err -1 [ 2.482539] gpio-574 (scl): gpio_set_open_drain_value_commit: Error in set_value for open drain err -1 I assume I must dig deeper here. Markus