linux-kernel - Re: [PATCH v2 2/6] ARM: dts: bcm283x: Define standard pinctrl groups in the gpio node.

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Date:   Mon, 12 Sep 2016 21:05:47 +0200 (CEST)
From:   Stefan Wahren <stefan.wahren@...e.com>
To:     Gerd Hoffmann <kraxel@...hat.com>,
        linux-arm-kernel@...ts.infradead.org,
        linux-rpi-kernel@...ts.infradead.org, devicetree@...r.kernel.org
Cc:     Scott Branden <sbranden@...adcom.com>, Ray Jui <rjui@...adcom.com>,
        Russell King <linux@...linux.org.uk>,
        open list <linux-kernel@...r.kernel.org>,
        Rob Herring <robh+dt@...nel.org>,
        bcm-kernel-feedback-list@...adcom.com,
        Mark Rutland <mark.rutland@....com>,
        Florian Fainelli <f.fainelli@...il.com>
Subject: Re: [PATCH v2 2/6] ARM: dts: bcm283x: Define standard pinctrl
 groups in the gpio node.

Hi Gerd,

> Stefan Wahren <stefan.wahren@...e.com> hat am 12. September 2016 um 20:19
> geschrieben:
> 
> 
> Hi Gerd,
> 
> > Gerd Hoffmann <kraxel@...hat.com> hat am 12. September 2016 um 10:22
> > geschrieben:
> > 
> > 
> > From: Eric Anholt <eric@...olt.net>
> > 
> > The BCM2835-ARM-Peripherals.pdf documentation specifies what the
> > function selects do for the pins, and there are a bunch of obvious
> > groupings to be made.  With these created, we'll be able to replace
> > bcm2835-rpi.dtsi's main "set all of these pins to alt0" with
> > references to specific groups we want enabled.
> > 
> > Signed-off-by: Eric Anholt <eric@...olt.net>
> > 
> > squashed in:
> >   ARM: dts: bcm283x: Add the emmc pin group to bcm283x.dtsi.
> >   ARM: dts: bcm283x: Add a group for mapping pins 48-53 to sdhost.
> >   ARM: dts: bcm283x: Add a new EMMC pin group from the downstream tree.
> > 
> > fixups by kraxel:
> >   * fix spi0 name
> >   * sort & group entries
> >   * use pull defines
> >   * add dpi group
> 
> this looks like a changelog. Please move this at the proper place before the
> first "diff" and specify the version.
> 
> > 
> > Signed-off-by: Gerd Hoffmann <kraxel@...hat.com>
> > ---
> >  arch/arm/boot/dts/bcm283x.dtsi | 203
> > +++++++++++++++++++++++++++++++++++++++++
> >  1 file changed, 203 insertions(+)
> > 
> > diff --git a/arch/arm/boot/dts/bcm283x.dtsi b/arch/arm/boot/dts/bcm283x.dtsi
> > index 4d9f3ab..7b03b63 100644
> > --- a/arch/arm/boot/dts/bcm283x.dtsi
> > +++ b/arch/arm/boot/dts/bcm283x.dtsi
> > @@ -131,6 +131,209 @@
> >  
> >  			interrupt-controller;
> >  			#interrupt-cells = <2>;
> > +
> > +			/* Defines pin muxing groups according to
> > +			 * BCM2835-ARM-Peripherals.pdf page 102.
> > +			 *
> > +			 * While each pin can have its mux selected
> > +			 * for various functions individually, some
> > +			 * groups only make sense to switch to a
> > +			 * particular function together.
> > +			 */
> > +			dpi_gpio4: dpi_gpio4 {
> > +				brcm,pins = <0 1 2 3 4 5 6 7 8 9 10 11
> > +					     12 13 14 15 16 17 18 19
> > +					     20 21 22 23 24 25 26 27>;
> > +				brcm,function = <BCM2835_FSEL_ALT2>;
> > +			};
> 
> s/dpi_gpio4/dpi_gpio0
> 
> > +			emmc_gpio22: emmc_gpio22 {
> > +				brcm,pins = <22 23 24 25 26 27>;
> > +				brcm,function = <BCM2835_FSEL_ALT3>;
> > +			};
> > +			emmc_gpio34: emmc_gpio34 {
> > +				brcm,pins = <34 35 36 37 38 39>;
> > +				brcm,function = <BCM2835_FSEL_ALT3>;
> > +				brcm,pull = <BCM2835_PUD_OFF
> > +					     BCM2835_PUD_UP
> > +					     BCM2835_PUD_UP
> > +					     BCM2835_PUD_UP
> > +					     BCM2835_PUD_UP
> > +					     BCM2835_PUD_UP>;
> > +			};
> > +			emmc_gpio48: emmc_gpio48 {
> > +				brcm,pins = <48 49 50 51 52 53>;
> > +				brcm,function = <BCM2835_FSEL_ALT3>;
> > +			};
> 
> Sorry, i didn't notice this before. The naming of these groups suggest 3 muxes
> for the same eMMC interface. I thought there is a eMMC interface and a SD host
> interface with different DMA channels.
> 
> > +
> > ...
> > +
> > +			sdhost_gpio48: sdhost_gpio48 {
> > +				brcm,pins = <48 49 50 51 52 53>;
> > +				brcm,function = <BCM2835_FSEL_ALT0>;
> > +			};
> 
> I think this incorrect. There is no function ALT0 for these pins, only ALT3.

please forget my last 2 comments. According to this page [1] eMMC is selected by
ALT3 and sdhost is selected by ALT0.

Do you know a reliable source where all muxes for both interface are documented?
The datasheet isn't very helpful here.

Regards
Stefan

[1] - http://pinout.xyz/pinout/sdio

> 
> Regards
> Stefan