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Date: Mon, 27 Oct 2014 01:27:15 +0100 From: Heiko Stübner <heiko@...ech.de> To: Julien CHAUVEAU <julien.chauveau@...-technologies.fr> Cc: Rob Herring <robh+dt@...nel.org>, Pawel Moll <pawel.moll@....com>, Mark Rutland <mark.rutland@....com>, Ian Campbell <ijc+devicetree@...lion.org.uk>, Kumar Gala <galak@...eaurora.org>, Russell King <linux@....linux.org.uk>, "moderated list:ARM/Rockchip SoC..." <linux-arm-kernel@...ts.infradead.org>, "open list:ARM/Rockchip SoC..." <linux-rockchip@...ts.infradead.org>, "open list:OPEN FIRMWARE AND..." <devicetree@...r.kernel.org>, open list <linux-kernel@...r.kernel.org> Subject: Re: [PATCH] ARM: dts: rockchip: use internal pull-up resistors on I2C busses Hi Julien, Am Freitag, 17. Oktober 2014, 16:40:30 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 resistors > 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@...alhost:~# i2cdetect 3 > > WARNING! This program can confuse your I2C bus, cause data loss and worse! > I will probe file /dev/i2c-3. > I will probe address range 0x03-0x77. > Continue? [Y/n] > 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 > -- rk3x-i2c 2005a000.i2c: timeout, ipd: 0x80, state: 3 > ... > > (2) root@...alhost:~# i2cdetect 3 > > WARNING! This program can confuse your I2C bus, cause data loss and worse! > I will probe file /dev/i2c-3. > I will probe address range 0x03-0x77. > Continue? [Y/n] > 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 <julien.chauveau@...-technologies.fr> > --- > 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..c5cdf55 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 = <RK_GPIO2 28 RK_FUNC_1 &pcfg_pull_none>, > - <RK_GPIO2 29 RK_FUNC_1 &pcfg_pull_none>; > + rockchip,pins = <RK_GPIO2 28 RK_FUNC_1 &pcfg_pull_up>, > + <RK_GPIO2 29 RK_FUNC_1 &pcfg_pull_up>; The rk3066a does not support distinguishing between up and down pulls. On it only &pcfg_pull_default is possible that configures the pull to a pin-specific pull direction. For the i2c pins the direction is (of course) "up". Heiko -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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