Hello Marek,
On 01/25/2017 04:13 AM, Marek Szyprowski wrote:
> Hi Javier,
>
>
> On 2017-01-24 18:57, Javier Martinez Canillas wrote:
>> Hello Krzysztof,
>>
>> On 01/24/2017 02:52 PM, Krzysztof Kozlowski wrote:
>>> On Tue, Jan 24, 2017 at 01:45:28PM +0100, Andrzej Hajda wrote:
>>>> LDO7 regulator beside DSI and HDMI provides power for core blocks in Exynos
>>>> 5433 SoC. Disabling it causes serious current leak - about 200mA.
>>>>
>>>> Signed-off-by: Andrzej Hajda <a.hajda@xxxxxxxxxxx>
>>>> ---
>>>> arch/arm64/boot/dts/exynos/exynos5433-tm2-common.dtsi | 4 ++++
>>>> 1 file changed, 4 insertions(+)
>>>>
>>>> diff --git a/arch/arm64/boot/dts/exynos/exynos5433-tm2-common.dtsi b/arch/arm64/boot/dts/exynos/exynos5433-tm2-common.dtsi
>>>> index 5f1e172..b22bec8 100644
>>>> --- a/arch/arm64/boot/dts/exynos/exynos5433-tm2-common.dtsi
>>>> +++ b/arch/arm64/boot/dts/exynos/exynos5433-tm2-common.dtsi
>>>> @@ -432,6 +432,10 @@
>>>> regulator-name = "VDD18_MIPI2L_1.8V_AP";
>>>> regulator-min-microvolt = <1800000>;
>>>> regulator-max-microvolt = <1800000>;
>> I see you already applied, but I think it would be good to have some comments
>> here explaining why the regulator should be always-on. Otherwise, in future a
>> developer might want to disable the regulator since it may think that is not
>> needed due dsi and hdmi already enabling it.
>
> If such change is added in a separate commit, one can easily find the reason
> using "git blame".
>
Yes, that's true.
>>>> + regulator-always-on;
>>>> + regulator-state-mem {
>>>> + regulator-off-in-suspend;
>>>> + };
>>> Thanks, applied.
>>>
>>> Just to satisfy my curiosity, how disabling the regulator causes current
>>> leak? What happens exactly?
>
> Such leakage usually happens if there is a hw block, which have more than one
> power supply. Disabling power for the one power supply might turn the hw logic
> into some meta state, in which it still conduct a current from the other source.
>
> The best example of such behavior is Odroid U3 and its problems with reset when
> HDMI cable is connected. Sometimes the current leaks from the HDMI connector to
> the board when the main power supply is turned off and the board enters some
> kind of a a "meta state".
>
I didn't know about all this, thanks a lot for the explanation.
> We still have no idea which hw block causes this leakage in case of TM2/TM2e
> though.
>
> Best regards
Best regards,
--
Javier Martinez Canillas
Open Source Group
Samsung Research America
--
To unsubscribe from this list: send the line "unsubscribe linux-samsung-soc" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
