From mboxrd@z Thu Jan 1 00:00:00 1970 From: hdegoede@redhat.com (Hans de Goede) Date: Tue, 8 Sep 2015 14:49:33 +0200 Subject: [linux-sunxi] Re: [PATCH] ARM: dts: sun4i: Add dts file for the pov protab2-ips9 tablet In-Reply-To: References: <1441441319-10658-1-git-send-email-hdegoede@redhat.com> <20150906163023.GR31584@lukather> <55ED3739.609@redhat.com> <20150907205603.GX31584@lukather> <55EE9230.70209@redhat.com> Message-ID: <55EED95D.20004@redhat.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org Hi, On 09/08/2015 10:40 AM, Chen-Yu Tsai wrote: > On Tue, Sep 8, 2015 at 3:45 PM, Hans de Goede wrote: >> Hi, >> >> On 07-09-15 22:56, Maxime Ripard wrote: >>> >>> On Mon, Sep 07, 2015 at 09:05:29AM +0200, Hans de Goede wrote: >>>>>> >>>>>> +®_ldo3 { >>>>>> + /* >>>>>> + * We need to always power the camera sensor, otherwhise all >>>>>> access >>>>>> + * to i2c1 is blocked. >>>>>> + */ >>>>>> + regulator-always-on; >>>>>> + regulator-min-microvolt = <2800000>; >>>>>> + regulator-max-microvolt = <2800000>; >>>>>> + regulator-name = "vdd-csi"; >>>>>> +}; >>>>> >>>>> >>>>> What is connected on i2c1 ? Just the camera sensor? or it has some >>>>> other devices there? >>>> >>>> >>>> The bma250 accelerometer sits there, and the kernel already has a driver >>>> for it. That driver needs to have devicetree binding support added, and >>>> then we should be able to use the accelerometer. >>> >>> >>> Ok, so if this regulator is disable, you can't access the other >>> devices as well, right? >> >> >> Right, the controller reports the bus as being stuck. >> >>> Do you know why? Is it the regulator providing >>> the pull-up voltage? >> >> >> I've tried enabling the pull ups on the SoC i2c pins, so I do not think >> that it is that, it seems that somehow when not powered the camera sensor is >> actively keeping the lines low. Either it has multiple power planes, or >> it is using normally-on fet-s between ground and its i2c lines. > > FYI the reference designs use one regulator to power the pull-ups, VCC-PX > (X for X pin group), and VDDIO (IO power)on the camera sensors. AVDD, DVDD > (actual power) for the sensors are another (or more) regulators. But that is a A23 or some such generation thing, right? This is an A10 based tablet! Regards, Hans