From mboxrd@z Thu Jan 1 00:00:00 1970 From: Karl Palsson Subject: Re: [PATCH v2] ARM: dts: rockchip: use internal pull-up resistors on I2C busses Date: Wed, 29 Oct 2014 13:44:15 +0000 Message-ID: <20141029134415.GA3499@palmtree.beeroclock.net> References: <1414492597-13566-1-git-send-email-julien.chauveau@neo-technologies.fr> <2234299.BSD6RSf1dG@diego> Mime-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Return-path: Content-Disposition: inline In-Reply-To: <2234299.BSD6RSf1dG@diego> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=m.gmane.org@lists.infradead.org To: Heiko =?iso-8859-1?Q?St=FCbner?= Cc: Mark Rutland , "open list:OPEN FIRMWARE AND..." , Addy Ke , Russell King , Pawel Moll , wsa@the-dreams.de, Max Schwarz , open list , "open list:ARM/Rockchip SoC..." , Rob Herring , Julien CHAUVEAU , Kumar Gala , Ian Campbell , "moderated list:ARM/Rockchip SoC..." List-Id: devicetree@vger.kernel.org I'd be more inclined to have pulls disabled by default, it's more standard = with what smaller micros do, but I've no experience with these bigger cortex-a parts. It's a= lso the "least surprise" path. If you want to try and use the onboard pullups, you can sp= ecify that in your board file, but for people deliberately selecting pullups for their timing = and load expectations, being required to take an extra step to turn off something seems unexpected= . = If you _want_ to be able to probe an i2c bus for devices added aftermarket,= on a board that didn't get i2c pull ups because no devices were planned, and you want to tu= rn on the internal pullups for that, I think that's something you need to do yourself, not mak= ing it a hard default in the SoC dtsi file. so, if it's off by default, you get this dtsi dts Board1, i2c periphs, designed pullups =3D> off - board2, no peripsh, pulls in case =3D> off - board3, no periphs, forgot pulls, pray=3D> off on If you turn it on by default, sure, it causes no harm in most cases, but yo= u're no longer getting the values you expect, without having to turn off things that are not defau= lt anyway. Sincerely, Karl Palsson On Wed, Oct 29, 2014 at 02:17:23PM +0100, Heiko St=FCbner wrote: > Hi Addy, Max, Wolfram, > = > after Doug's explanation of disfavour [0] and Julien's subsequent respons= e I'm > not sure which direction to go. So if possible I'd like to collect some m= ore > opinions of people knowing a lot more about i2c internals than myself :-)= . > = > = > Thanks > Heiko > = > = > [0] http://lists.infradead.org/pipermail/linux-rockchip/2014-October/0009= 34.html > = > Am Dienstag, 28. Oktober 2014, 11:36:36 schrieb Julien CHAUVEAU: > > According to the I2C bus specification, it is required to use pull-up > > resistors on the clock and data lines. Probing the I2C busses with > > i2cdetect results in bad results when no devices are connected and no > > external resistors are used. > > = > > This patch configures the I2C busses to use the internal pull-up resist= ors > > on the RK3066, RK3188 and RK3288 Rockchip processors. It should also be > > noted that these default pull settings match the original configuration= on > > these SoCs. > > = > > Below is the results of using i2cdetect on a I2C bus with no devices > > connected before (1) and after (2) applying this patch. > > = > > (1) root@localhost:~# i2cdetect -y 3 > > 0 1 2 3 4 5 6 7 8 9 a b c d e f > > 00: 03 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f > > 10: 10 11 12 13 14 15 16 17 18 19 1a 1b 1c 1d 1e 1f > > 20: 20 21 22 23 24 25 26 27 28 29 2a 2b 2c 2d 2e 2f > > 30: -- -- -- -- -- rk3x-i2c 2005a000.i2c: timeout, ipd: 0x81, state: 2 > > -- rk3x-i2c 2005a000.i2c: timeout, ipd: 0x80, state: 2 > > -- rk3x-i2c 2005a000.i2c: timeout, ipd: 0x80, state: 2 > > -- rk3x-i2c 2005a000.i2c: timeout, ipd: 0x80, state: 3 > > -- rk3x-i2c 2005a000.i2c: timeout, ipd: 0x80, state: 3 > > -- rk3x-i2c 2005a000.i2c: timeout, ipd: 0x80, state: 3 > > ... > > = > > (2) root@localhost:~# i2cdetect -y 3 > > 0 1 2 3 4 5 6 7 8 9 a b c d e f > > 00: -- -- -- -- -- -- -- -- -- -- -- -- -- > > 10: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- > > 20: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- > > 30: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- > > 40: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- > > 50: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- > > 60: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- > > 70: -- -- -- -- -- -- -- -- > > = > > Signed-off-by: Julien CHAUVEAU > > --- > > Changes since v1: > > - fix the rk3066a pull settings (only available is pull_none/pull_defau= lt) > > - remove the warnings in the results of i2cdetect > > = > > arch/arm/boot/dts/rk3066a.dtsi | 20 ++++++++++---------- > > arch/arm/boot/dts/rk3188.dtsi | 20 ++++++++++---------- > > arch/arm/boot/dts/rk3288.dtsi | 24 ++++++++++++------------ > > 3 files changed, 32 insertions(+), 32 deletions(-) > > = > > diff --git a/arch/arm/boot/dts/rk3066a.dtsi b/arch/arm/boot/dts/rk3066a= .dtsi > > index ad9c2db..dbc1a0b 100644 > > --- a/arch/arm/boot/dts/rk3066a.dtsi > > +++ b/arch/arm/boot/dts/rk3066a.dtsi > > @@ -202,36 +202,36 @@ > > = > > i2c0 { > > i2c0_xfer: i2c0-xfer { > > - rockchip,pins =3D , > > - ; > > + rockchip,pins =3D , > > + ; > > }; > > }; > > = > > i2c1 { > > i2c1_xfer: i2c1-xfer { > > - rockchip,pins =3D , > > - ; > > + rockchip,pins =3D , > > + ; > > }; > > }; > > = > > i2c2 { > > i2c2_xfer: i2c2-xfer { > > - rockchip,pins =3D , > > - ; > > + rockchip,pins =3D , > > + ; > > }; > > }; > > = > > i2c3 { > > i2c3_xfer: i2c3-xfer { > > - rockchip,pins =3D , > > - ; > > + rockchip,pins =3D , > > + ; > > }; > > }; > > = > > i2c4 { > > i2c4_xfer: i2c4-xfer { > > - rockchip,pins =3D , > > - ; > > + rockchip,pins =3D , > > + ; > > }; > > }; > > = > > diff --git a/arch/arm/boot/dts/rk3188.dtsi b/arch/arm/boot/dts/rk3188.d= tsi > > index ddaada7..ee2865f 100644 > > --- a/arch/arm/boot/dts/rk3188.dtsi > > +++ b/arch/arm/boot/dts/rk3188.dtsi > > @@ -188,36 +188,36 @@ > > = > > i2c0 { > > i2c0_xfer: i2c0-xfer { > > - rockchip,pins =3D , > > - ; > > + rockchip,pins =3D , > > + ; > > }; > > }; > > = > > i2c1 { > > i2c1_xfer: i2c1-xfer { > > - rockchip,pins =3D , > > - ; > > + rockchip,pins =3D , > > + ; > > }; > > }; > > = > > i2c2 { > > i2c2_xfer: i2c2-xfer { > > - rockchip,pins =3D , > > - ; > > + rockchip,pins =3D , > > + ; > > }; > > }; > > = > > i2c3 { > > i2c3_xfer: i2c3-xfer { > > - rockchip,pins =3D , > > - ; > > + rockchip,pins =3D , > > + ; > > }; > > }; > > = > > i2c4 { > > i2c4_xfer: i2c4-xfer { > > - rockchip,pins =3D , > > - ; > > + rockchip,pins =3D , > > + ; > > }; > > }; > > = > > diff --git a/arch/arm/boot/dts/rk3288.dtsi b/arch/arm/boot/dts/rk3288.d= tsi > > index 874e66d..9a4b1f7 100644 > > --- a/arch/arm/boot/dts/rk3288.dtsi > > +++ b/arch/arm/boot/dts/rk3288.dtsi > > @@ -636,43 +636,43 @@ > > = > > i2c0 { > > i2c0_xfer: i2c0-xfer { > > - rockchip,pins =3D <0 15 RK_FUNC_1 &pcfg_pull_none>, > > - <0 16 RK_FUNC_1 &pcfg_pull_none>; > > + rockchip,pins =3D <0 15 RK_FUNC_1 &pcfg_pull_up>, > > + <0 16 RK_FUNC_1 &pcfg_pull_up>; > > }; > > }; > > = > > i2c1 { > > i2c1_xfer: i2c1-xfer { > > - rockchip,pins =3D <8 4 RK_FUNC_1 &pcfg_pull_none>, > > - <8 5 RK_FUNC_1 &pcfg_pull_none>; > > + rockchip,pins =3D <8 4 RK_FUNC_1 &pcfg_pull_up>, > > + <8 5 RK_FUNC_1 &pcfg_pull_up>; > > }; > > }; > > = > > i2c2 { > > i2c2_xfer: i2c2-xfer { > > - rockchip,pins =3D <6 9 RK_FUNC_1 &pcfg_pull_none>, > > - <6 10 RK_FUNC_1 &pcfg_pull_none>; > > + rockchip,pins =3D <6 9 RK_FUNC_1 &pcfg_pull_up>, > > + <6 10 RK_FUNC_1 &pcfg_pull_up>; > > }; > > }; > > = > > i2c3 { > > i2c3_xfer: i2c3-xfer { > > - rockchip,pins =3D <2 16 RK_FUNC_1 &pcfg_pull_none>, > > - <2 17 RK_FUNC_1 &pcfg_pull_none>; > > + rockchip,pins =3D <2 16 RK_FUNC_1 &pcfg_pull_up>, > > + <2 17 RK_FUNC_1 &pcfg_pull_up>; > > }; > > }; > > = > > i2c4 { > > i2c4_xfer: i2c4-xfer { > > - rockchip,pins =3D <7 17 RK_FUNC_1 &pcfg_pull_none>, > > - <7 18 RK_FUNC_1 &pcfg_pull_none>; > > + rockchip,pins =3D <7 17 RK_FUNC_1 &pcfg_pull_up>, > > + <7 18 RK_FUNC_1 &pcfg_pull_up>; > > }; > > }; > > = > > i2c5 { > > i2c5_xfer: i2c5-xfer { > > - rockchip,pins =3D <7 19 RK_FUNC_1 &pcfg_pull_none>, > > - <7 20 RK_FUNC_1 &pcfg_pull_none>; > > + rockchip,pins =3D <7 19 RK_FUNC_1 &pcfg_pull_up>, > > + <7 20 RK_FUNC_1 &pcfg_pull_up>; > > }; > > }; > = > = > _______________________________________________ > Linux-rockchip mailing list > Linux-rockchip@lists.infradead.org > http://lists.infradead.org/mailman/listinfo/linux-rockchip