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Date: Sat, 4 Jan 2020 22:39:48 +0000 From: Peter Rosin <peda@...ntia.se> To: "Codrin.Ciubotariu@...rochip.com" <Codrin.Ciubotariu@...rochip.com>, "linux-i2c@...r.kernel.org" <linux-i2c@...r.kernel.org>, "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>, "linux-arm-kernel@...ts.infradead.org" <linux-arm-kernel@...ts.infradead.org>, "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org> CC: "kamel.bouhara@...tlin.com" <kamel.bouhara@...tlin.com>, "wsa@...-dreams.de" <wsa@...-dreams.de>, "Nicolas.Ferre@...rochip.com" <Nicolas.Ferre@...rochip.com>, "alexandre.belloni@...tlin.com" <alexandre.belloni@...tlin.com>, "Ludovic.Desroches@...rochip.com" <Ludovic.Desroches@...rochip.com>, "robh@...nel.org" <robh@...nel.org> Subject: Re: [PATCH v2 4/6] ARM: at91/dt: sama5d3: add i2c gpio pinctrl On 2020-01-03 10:49, Codrin.Ciubotariu@...rochip.com wrote: > From: Kamel Bouhara <kamel.bouhara@...tlin.com> > > Add the i2c gpio pinctrls to support the i2c bus recovery > > Signed-off-by: Kamel Bouhara <kamel.bouhara@...tlin.com> > --- > > Changes in v2: > - none; > > arch/arm/boot/dts/sama5d3.dtsi | 33 ++++++++++++++++++++++++++++++--- > 1 file changed, 30 insertions(+), 3 deletions(-) > *snip* > @@ -639,6 +648,12 @@ > <AT91_PIOA 30 AT91_PERIPH_A AT91_PINCTRL_NONE /* PA30 periph A TWD0 pin, conflicts with URXD1, ISI_VSYNC */ > AT91_PIOA 31 AT91_PERIPH_A AT91_PINCTRL_NONE>; /* PA31 periph A TWCK0 pin, conflicts with UTXD1, ISI_HSYNC */ > }; > + > + pinctrl_i2c0_gpio: i2c0-gpio { > + atmel,pins = > + <AT91_PIOA 30 AT91_PERIPH_GPIO AT91_PINCTRL_PULL_UP > + AT91_PIOA 31 AT91_PERIPH_GPIO AT91_PINCTRL_PULL_UP>; > + }; I'm curious, but why are pull-ups suddenly needed just because the pins are used for GPIO recovery? Why are pull-ups not needed when the pins are used by the I2C peripheral device(s)? Given figure 27-2 "I/O Line Control Logic" in my SAMA5D3 datasheet, I see no difference as to how and why the pull-ups are applied depending on what the current function of the pin is. So, if the I2C bus works w/o pulls, bus recovery using GPIO must also work w/o pulls. I.e. the device tree requires you to have external pull-ups on the I2C bus anyway, so why bother with internal pull-ups for the recovery case? Changing pull-up settings just for recovery feels like something that will inevitably create hard to debug surprises at the least opportune time... Or am I missing something? (I'm focusing on SAMA5D3 since that is what I happen to work with, but the same question appears to apply for SAMA5D2 and SAMA5D4...) Cheers, Peter
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