Subject: [linux-sunxi] Re: [PATCH] ARM: dts: sun4i: Add dts file for the pov protab2-ips9 tablet

From: [email-masked] (Hans de Goede)
Date: Tue, 8 Sep 2015 14:49:33 +0200

Hi,

On 09/08/2015 10:40 AM, Chen-Yu Tsai wrote:
> On Tue, Sep 8, 2015 at 3:45 PM, Hans de Goede <[email-masked]> 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:
>>>>>>
>>>>>> +&reg_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