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Date: Wed, 17 Sep 2014 07:17:03 -0500
From: "Peter A. Bigot" <pab@pabigot.com>
Organization: Peter Bigot Consulting, LLC
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Subject: Re: mis-definition of SLEWCTRL_FAST in dt-bindings amxxxx header
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Any comment on this?  I have a patch, but figured it'd be better for TI 
to provide an official solution.  Or is there another forum it should be 
raised in?

It's really misleading for the self-documenting device tree 
specifications to lie about what sort of slew is being configured.

Peter

On 09/06/2014 06:17 PM, Peter A. Bigot wrote:
> While converting some old DTS bindings, I noticed that the Linux 
> include/dt-bindings/pinctrl/am33xx.h and am43xx.h headers both define 
> SLEWCTRL_FAST constants:
>
> include/dt-bindings/pinctrl/am33xx.h:#define 
> SLEWCTRL_FAST              (1 << 6)
> include/dt-bindings/pinctrl/am43xx.h:#define 
> SLEWCTRL_FAST              (1 << 19)
>
> According to the TRM for these processors, the effect of setting that 
> bit is to select slow slew; fast would be selected by leaving it 
> cleared.  The constants should therefore be named SLEWCTRL_SLOW.
>
> This is consistent with the value for the I2C binding constants I'm 
> converting:
>
> beagleboard/3.14:arch/arm/boot/dts/am335x-bone-common-pinmux.dtsi: 
> 0x158 0x72      /* spi0_d1.i2c1_sda, SLEWCTRL_SLOW | INPUT_PULLUP | 
> MODE2 */
> beagleboard/3.14:arch/arm/boot/dts/am335x-bone-common-pinmux.dtsi: 
> 0x15c 0x72      /* spi0_cs0.i2c1_scl, SLEWCTRL_SLOW | INPUT_PULLUP | 
> MODE2 */
>
> except that in the official files we have something like:
>
> stable/linux-3.14.y:arch/arm/boot/dts/am43x-epos-evm.dts: 0x188 
> (PIN_INPUT_PULLUP | SLEWCTRL_FAST | MUX_MODE0)    /* i2c0_sda.i2c0_sda */
> stable/linux-3.14.y:arch/arm/boot/dts/am43x-epos-evm.dts: 0x18c 
> (PIN_INPUT_PULLUP | SLEWCTRL_FAST | MUX_MODE0)    /* i2c0_scl.i2c0_scl */
>
> which is either wrong or misleading.
>
> Peter