Re: [PATCH v2 2/3] ARM: dts: exynos: Define vqmmc for eMMC card on Odroid X/X2/U3

[Javier Martinez Canillas]

Hello Krzysztof,

On Thu, Apr 28, 2016 at 1:50 AM, Krzysztof Kozlowski
<k.kozlowski@xxxxxxxxxxx> wrote:
> On 04/27/2016 11:29 PM, Javier Martinez Canillas wrote:
>> Hello Krzysztof,
>>
>> On 04/27/2016 10:00 AM, Krzysztof Kozlowski wrote:
>>> The eMMC card vmmc-supply contained incorrectly two regulators: LDO20
>>> and buck8. The second one is ignored. Additionally the buck8 is a vqmmc
>>> supply only on X and X2. On U3 the buck8 is providing power to the LAN
>>> (SMSC95xx) so instead the LDO22 should be used.
>>>
>>> Fix this by defining proper vmmc and vqmmc supplies for respective
>>> boards.
>>>
>>> Signed-off-by: Krzysztof Kozlowski <k.kozlowski@xxxxxxxxxxx>
>>>
>>> ---
>>>
>>> Changes since v1:
>>> 1. buck8 is used on X/X2 so differentiate the configuration (hint by
>>>    Tobias Jakobi).
>>> ---
>>>  arch/arm/boot/dts/exynos4412-odroid-common.dtsi | 13 ++++++++++---
>>>  arch/arm/boot/dts/exynos4412-odroidu3.dts       | 18 ++++++++++++++++++
>>>  arch/arm/boot/dts/exynos4412-odroidx.dts        | 11 +++++++++++
>>>  arch/arm/boot/dts/exynos4412-odroidx2.dts       | 11 +++++++++++
>>>  4 files changed, 50 insertions(+), 3 deletions(-)
>>>
>>> diff --git a/arch/arm/boot/dts/exynos4412-odroid-common.dtsi b/arch/arm/boot/dts/exynos4412-odroid-common.dtsi
>>> index 3d0d44581fbd..34a5b3daced0 100644
>>> --- a/arch/arm/boot/dts/exynos4412-odroid-common.dtsi
>>> +++ b/arch/arm/boot/dts/exynos4412-odroid-common.dtsi
>>> @@ -347,6 +347,13 @@
>>>                              regulator-boot-on;
>>>                      };
>>>
>>> +                    ldo22_reg: LDO22 {
>>> +                            regulator-name = "LDO22";
>>> +                            regulator-min-microvolt = <800000>;
>>> +                            regulator-max-microvolt = <3950000>;
>>> +                            regulator-boot-on;
>>> +                    };
>>> +
>>
>> I don't have a datasheet for the max77686 but I guess these min and max
>> values are the actual voltage range that the ldo22 regulator can support?
>
> Yes.
>
>> If that's the case, then I don't think setting these are correct since the
>> DT binding says that the regulator-{min,max}-microvolt properties describe
>> the voltage range that consumers may set. I've seen Mark mention this many
>> times, the last one I remember is at [0].
>
> For LDO22 there is no consumer so these are the constraints. Leaving

That was my point, there's no consumers for X/X2 and there is only a
consumer in U3 (vqmmc-supply for mshc_0) added by $SUBJECT. That's why
I thought that it should be defined in odroidu3.dts and removed from
the .dtsi.

> them undefined (here and in DTS for X/X2) would result in the same
> effect. The point is that these values are valid constraints. Please
> have in mind that the binding describe this as "smallest/largest voltage
> consumer may set" which is true for the code above.
>
>>
>> Probably would be better to leave the ldo22_reg definition to odroidu3.dts
>> to avoid setting these constraint in a .dtsi file.
>
> What about X/X2?
>

Mmm, I see what you mean. If the regulators are not defined then these
for example won't be turned off by the regulator subsystem if were
enabled by the bootloader. Then I guess your change makes sense.

>>>                      ldo25_reg: LDO25 {
>>>                              regulator-name = "VDDQ_LCD_1.8V";
>>>                              regulator-min-microvolt = <1800000>;
>>> @@ -411,8 +418,8 @@
>>>
>>>                      buck8_reg: BUCK8 {
>>>                              regulator-name = "BUCK8_2.8V";
>>> -                            regulator-min-microvolt = <2800000>;
>>> -                            regulator-max-microvolt = <2800000>;
>>> +                            regulator-min-microvolt = <750000>;
>>> +                            regulator-max-microvolt = <3900000>;
>>
>> Same here, since not all boards have the same constraint for this regulator,
>> it would be better to remove it from the .dtsi and let each dts to define it.
>
> Since all of the boards define them, it does not bring any difference
> having it here... so I can remove them.
>
>

Ok. I don't have a strong opinion on this though now that I realized
that not defining some regulators could lead to unused ones not being
disabled on boot.

>>>                      };
>>>              };
>>>      };
>>> @@ -456,7 +463,7 @@
>>>  &mshc_0 {
>>>      pinctrl-0 = <&sd4_clk &sd4_cmd &sd4_bus4 &sd4_bus8>;
>>>      pinctrl-names = "default";
>>> -    vmmc-supply = <&ldo20_reg &buck8_reg>;
>>> +    vmmc-supply = <&ldo20_reg>;
>>>      mmc-pwrseq = <&emmc_pwrseq>;
>>>      status = "okay";
>>>
>>> diff --git a/arch/arm/boot/dts/exynos4412-odroidu3.dts b/arch/arm/boot/dts/exynos4412-odroidu3.dts
>>> index dd89f7b37c9f..d73aa6c58fe3 100644
>>> --- a/arch/arm/boot/dts/exynos4412-odroidu3.dts
>>> +++ b/arch/arm/boot/dts/exynos4412-odroidu3.dts
>>> @@ -69,6 +69,24 @@
>>>      };
>>>  };
>>>
>>> +/* Supply for LAN9730/SMSC95xx */
>>> +&buck8_reg {
>>> +    regulator-name = "BUCK8_P3V3";
>>
>> I think it would be better to name it "BUCK8_3.3V" for consistency.
>
> Consistency of naming is nice but in the same time we want the regulator
> names to match the hardware because it is easier to read the code and
> check the schematics. On the schematics this is unfortunately called
> P3V3. :)
>

oh, I missed that. It's pity but I agree with you that matching the
schematics is more important that naming consistency.

Thanks a lot for your explanations, the patch looks good to me as it is now:

Reviewed-by: Javier Martinez Canillas <javier@xxxxxxxxxxxxxxx>

Best regards,
Javier