| Message ID | 1360778532-7480-2-git-send-email-dianders@chromium.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On 02/13/2013 11:02 AM, Doug Anderson wrote: > We need to use the i2c-arbitrator to talk to any of the devices on i2c > bus 4 on exynos5250-snow so that we don't confuse the embedded > controller (EC). Add the i2c-arbitrator to the device tree. As we > add future devices (keyboard, sbs, tps65090) we'll add them on top of > this. > > The arbitrated bus is numbered 104 simply as a convenience to make it > easier for people poking around to guess that it might have something > to do with the physical bus 4. > > The addition is split between the cros5250-common and the snow device > tree file since not all cros5250-class devices use arbitration. > diff --git a/arch/arm/boot/dts/cros5250-common.dtsi b/arch/arm/boot/dts/cros5250-common.dtsi > i2c@12CA0000 { > - status = "disabled"; > + samsung,i2c-sda-delay = <100>; > + samsung,i2c-max-bus-freq = <66000>; Shouldn't that use the standard clock-frequency property? > diff --git a/arch/arm/boot/dts/exynos5250-snow.dts b/arch/arm/boot/dts/exynos5250-snow.dts > + i2c-arbitrator { > + compatible = "i2c-arbitrator"; > + #address-cells = <1>; > + #size-cells = <0>; > + /* Use ID 104 as a hint that we're on physical bus 4 */ > + i2c_104: i2c@0 { Does something use that hint? It sounds a little odd.
Stephen, On Wed, Feb 13, 2013 at 1:04 PM, Stephen Warren <swarren@wwwdotorg.org> wrote: > On 02/13/2013 11:02 AM, Doug Anderson wrote: >> We need to use the i2c-arbitrator to talk to any of the devices on i2c >> bus 4 on exynos5250-snow so that we don't confuse the embedded >> controller (EC). Add the i2c-arbitrator to the device tree. As we >> add future devices (keyboard, sbs, tps65090) we'll add them on top of >> this. >> >> The arbitrated bus is numbered 104 simply as a convenience to make it >> easier for people poking around to guess that it might have something >> to do with the physical bus 4. >> >> The addition is split between the cros5250-common and the snow device >> tree file since not all cros5250-class devices use arbitration. > >> diff --git a/arch/arm/boot/dts/cros5250-common.dtsi b/arch/arm/boot/dts/cros5250-common.dtsi > >> i2c@12CA0000 { >> - status = "disabled"; >> + samsung,i2c-sda-delay = <100>; >> + samsung,i2c-max-bus-freq = <66000>; > > Shouldn't that use the standard clock-frequency property? At the moment this is the way that you specify it for the i2c controller we're using... >> diff --git a/arch/arm/boot/dts/exynos5250-snow.dts b/arch/arm/boot/dts/exynos5250-snow.dts > >> + i2c-arbitrator { >> + compatible = "i2c-arbitrator"; >> + #address-cells = <1>; >> + #size-cells = <0>; > >> + /* Use ID 104 as a hint that we're on physical bus 4 */ >> + i2c_104: i2c@0 { > > Does something use that hint? It sounds a little odd. The i2c bus numbering patches will end up creating "/dev/i2c-104". ...so the hint is really for developers who are poking around. It's definitely a strange number and that's part of the point. Right now there's nothing preventing someone from using 'i2cdetect' or 'i2cget' on bus 4 and bypassing arbitration. My hope was that having something crazy like "104" would help someone realize that it's a bad idea. ...besides, if I don't come up with _some_ number then this will get assigned the first unused ID which could be extra confusing. -Doug
On 02/13/2013 05:38 PM, Doug Anderson wrote: > Stephen, > > > On Wed, Feb 13, 2013 at 1:04 PM, Stephen Warren <swarren@wwwdotorg.org> wrote: >> On 02/13/2013 11:02 AM, Doug Anderson wrote: >>> We need to use the i2c-arbitrator to talk to any of the devices on i2c >>> bus 4 on exynos5250-snow so that we don't confuse the embedded >>> controller (EC). Add the i2c-arbitrator to the device tree. As we >>> add future devices (keyboard, sbs, tps65090) we'll add them on top of >>> this. >>> >>> The arbitrated bus is numbered 104 simply as a convenience to make it >>> easier for people poking around to guess that it might have something >>> to do with the physical bus 4. >>> >>> The addition is split between the cros5250-common and the snow device >>> tree file since not all cros5250-class devices use arbitration. >>> diff --git a/arch/arm/boot/dts/exynos5250-snow.dts b/arch/arm/boot/dts/exynos5250-snow.dts >> >>> + i2c-arbitrator { >>> + compatible = "i2c-arbitrator"; >>> + #address-cells = <1>; >>> + #size-cells = <0>; >> >>> + /* Use ID 104 as a hint that we're on physical bus 4 */ >>> + i2c_104: i2c@0 { >> >> Does something use that hint? It sounds a little odd. > > The i2c bus numbering patches will end up creating "/dev/i2c-104". Oh sorry, I see this is just the alias doing it's job. I'd misread that as the reg value being 104 and driving the bus ID.
diff --git a/arch/arm/boot/dts/cros5250-common.dtsi b/arch/arm/boot/dts/cros5250-common.dtsi index 46c0980..f451375 100644 --- a/arch/arm/boot/dts/cros5250-common.dtsi +++ b/arch/arm/boot/dts/cros5250-common.dtsi @@ -58,7 +58,10 @@ }; i2c@12CA0000 { - status = "disabled"; + samsung,i2c-sda-delay = <100>; + samsung,i2c-max-bus-freq = <66000>; + gpios = <&gpa2 0 3 3 0>, + <&gpa2 1 3 3 0>; }; i2c@12CB0000 { diff --git a/arch/arm/boot/dts/exynos5250-snow.dts b/arch/arm/boot/dts/exynos5250-snow.dts index 17dd951..69a87a0 100644 --- a/arch/arm/boot/dts/exynos5250-snow.dts +++ b/arch/arm/boot/dts/exynos5250-snow.dts @@ -16,6 +16,10 @@ model = "Google Snow"; compatible = "google,snow", "samsung,exynos5250"; + aliases { + i2c104 = &i2c_104; + }; + gpio-keys { compatible = "gpio-keys"; @@ -29,6 +33,26 @@ }; }; + i2c-arbitrator { + compatible = "i2c-arbitrator"; + #address-cells = <1>; + #size-cells = <0>; + + i2c-parent = <&{/i2c@12CA0000}>; + + bus-arbitration-gpios = <&gpf0 3 1 0 0>, <&gpe0 4 0 3 0>; + bus-arbitration-slew-delay-us = <10>; + bus-arbitration-wait-retry-us = <3000>; + bus-arbitration-wait-free-us = <50000>; + + /* Use ID 104 as a hint that we're on physical bus 4 */ + i2c_104: i2c@0 { + reg = <0>; + #address-cells = <1>; + #size-cells = <0>; + }; + }; + /* * On Snow we've got SIP WiFi and so can keep drive strengths low to * reduce EMI.
We need to use the i2c-arbitrator to talk to any of the devices on i2c bus 4 on exynos5250-snow so that we don't confuse the embedded controller (EC). Add the i2c-arbitrator to the device tree. As we add future devices (keyboard, sbs, tps65090) we'll add them on top of this. The arbitrated bus is numbered 104 simply as a convenience to make it easier for people poking around to guess that it might have something to do with the physical bus 4. The addition is split between the cros5250-common and the snow device tree file since not all cros5250-class devices use arbitration. Signed-off-by: Doug Anderson <dianders@chromium.org> --- Changes in v1: None arch/arm/boot/dts/cros5250-common.dtsi | 5 ++++- arch/arm/boot/dts/exynos5250-snow.dts | 24 ++++++++++++++++++++++++ 2 files changed, 28 insertions(+), 1 deletion(-)