Re: [PATCH v2 4/6] ARM: at91/dt: sama5d3: add i2c gpio pinctrl
From: <Codrin.Ciubotariu@microchip.com>
Date: 2020-01-06 16:58:49
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On 05.01.2020 00:39, Peter Rosin wrote:
On 2020-01-03 10:49, Codrin.Ciubotariu@microchip.com wrote:quoted
From: Kamel Bouhara <kamel.bouhara@bootlin.com> Add the i2c gpio pinctrls to support the i2c bus recovery Signed-off-by: Kamel Bouhara <kamel.bouhara@bootlin.com> --- Changes in v2: - none; arch/arm/boot/dts/sama5d3.dtsi | 33 ++++++++++++++++++++++++++++++--- 1 file changed, 30 insertions(+), 3 deletions(-)*snip*quoted
@@ -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...)
I don't think we need the pull-ups. I will remove them in v3. Thanks and best regards, Codrin _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel