[PATCH 3/7] ARM: shmobile: Disable DVS support for r8a7790

[PATCH 3/7] ARM: shmobile: Disable DVS support for r8a7790

[Gaku Inami]

Since range of VDD is narrow, there is no effect of power consumption
by DVS. So, DVS is disabled in R-CAR Gen2 series.

Signed-off-by: Gaku Inami <gaku.inami.xw@bp.renesas.com>
---
 arch/arm/boot/dts/r8a7790-lager.dts |    4 ----
 1 file changed, 4 deletions(-)

diff --git a/arch/arm/boot/dts/r8a7790-lager.dts b/arch/arm/boot/dts/r8a7790-lager.dts
index ab73ed0..9becef7 100644
--- a/arch/arm/boot/dts/r8a7790-lager.dts
+++ b/arch/arm/boot/dts/r8a7790-lager.dts
@@ -317,7 +317,3 @@
 	cd-gpios = <&gpio3 22 GPIO_ACTIVE_LOW>;
 	status = "okay";
 };
-
-&cpu0 {
-	cpu0-supply = <&vdd_dvfs>;
-};
-- 
1.7.9.5

Re: [PATCH 3/7] ARM: shmobile: Disable DVS support for r8a7790

[Sergei Shtylyov]

Hello.

On 05/29/2014 11:49 AM, Gaku Inami wrote:

> Since range of VDD is narrow, there is no effect of power consumption
> by DVS. So, DVS is disabled in R-CAR Gen2 series.

> Signed-off-by: Gaku Inami <gaku.inami.xw@bp.renesas.com>
> ---
>   arch/arm/boot/dts/r8a7790-lager.dts |    4 ----
>   1 file changed, 4 deletions(-)

> diff --git a/arch/arm/boot/dts/r8a7790-lager.dts b/arch/arm/boot/dts/r8a7790-lager.dts
> index ab73ed0..9becef7 100644
> --- a/arch/arm/boot/dts/r8a7790-lager.dts
> +++ b/arch/arm/boot/dts/r8a7790-lager.dts
> @@ -317,7 +317,3 @@
>   	cd-gpios = <&gpio3 22 GPIO_ACTIVE_LOW>;
>   	status = "okay";
>   };
> -
> -&cpu0 {
> -	cpu0-supply = <&vdd_dvfs>;
> -};

   Why enable it in the first place (patch #1)?

WBR, Sergei

Re: [PATCH 3/7] ARM: shmobile: Disable DVS support for r8a7790

[Gaku Inami]

Hi Sergei

>> diff --git a/arch/arm/boot/dts/r8a7790-lager.dts b/arch/arm/boot/dts/r8a7790-lager.dts
>> index ab73ed0..9becef7 100644
>> --- a/arch/arm/boot/dts/r8a7790-lager.dts
>> +++ b/arch/arm/boot/dts/r8a7790-lager.dts
>> @@ -317,7 +317,3 @@
>>   	cd-gpios = <&gpio3 22 GPIO_ACTIVE_LOW>;
>>   	status = "okay";
>>   };
>> -
>> -&cpu0 {
>> -	cpu0-supply = <&vdd_dvfs>;
>> -};
>    Why enable it in the first place (patch #1)?
>

patch #1 is created by Benoit. At the first, I thought better to
create a separate patch without changing his code. After that,
I understand that this method was wrong.

I will re-post by changing the patch #1. (disable DVS)

Re: [PATCH 3/7] ARM: shmobile: Disable DVS support for r8a7790

[Geert Uytterhoeven]

(CC Benoit)

On Thu, May 29, 2014 at 9:49 AM, Gaku Inami
<gaku.inami.xw@bp.renesas.com> wrote:
> Since range of VDD is narrow, there is no effect of power consumption
> by DVS. So, DVS is disabled in R-CAR Gen2 series.
>
> Signed-off-by: Gaku Inami <gaku.inami.xw@bp.renesas.com>
> ---
>  arch/arm/boot/dts/r8a7790-lager.dts |    4 ----
>  1 file changed, 4 deletions(-)
>
> diff --git a/arch/arm/boot/dts/r8a7790-lager.dts b/arch/arm/boot/dts/r8a7790-lager.dts
> index ab73ed0..9becef7 100644
> --- a/arch/arm/boot/dts/r8a7790-lager.dts
> +++ b/arch/arm/boot/dts/r8a7790-lager.dts
> @@ -317,7 +317,3 @@
>         cd-gpios = <&gpio3 22 GPIO_ACTIVE_LOW>;
>         status = "okay";
>  };
> -
> -&cpu0 {
> -       cpu0-supply = <&vdd_dvfs>;
> -};

The role of the DT is to describe the hardware.
Not using DVS because the effect of power consumption is low or non-existent
is a software policy.

So perhaps it should be kept?

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds

Re: [PATCH 3/7] ARM: shmobile: Disable DVS support for r8a7790

[Gaku Inami]

Hi Geert

Thank you for your feedback.

> The role of the DT is to describe the hardware.
> Not using DVS because the effect of power consumption is low or non-existent
> is a software policy.
>
> So perhaps it should be kept?

I understand what you mean. I will keep the setting of VDD into DT, 
and consider to disable DVS in a different way.

Re: [PATCH 3/7] ARM: shmobile: Disable DVS support for r8a7790

[Benoit Cousson]

Hi,

On 02/06/2014 05:14, Gaku Inami wrote:
> Hi Geert
>
> Thank you for your feedback.
>
>> The role of the DT is to describe the hardware.
>> Not using DVS because the effect of power consumption is low or non-existent
>> is a software policy.
>>
>> So perhaps it should be kept?
>
> I understand what you mean. I will keep the setting of VDD into DT,
> and consider to disable DVS in a different way.
>

Indeed, the line "cpu0-supply = <&vdd_dvfs>;" does just provide the name 
of the power rail that supply the ca15 cluster.

The postfix _dvfs is a little bit misleading in this case, I do agree.

If you do no want voltage scaling, it is just a matter of keeping the 
same voltage in the OPP table. This is what I have done in the series I 
sent a while back.

That being said, what is the exact voltage range supported by the CPU?
AFAIR, with 28nm process some SoCs are able to scale down to 0.9v.

Thanks,
Benoit

-- 
Benoît Cousson
BayLibre
Embedded Linux Technology Lab
www.baylibre.com

Re: [PATCH 3/7] ARM: shmobile: Disable DVS support for r8a7790

[Gaku Inami]

Hi Benoit

Thank you for your feedback.

> Indeed, the line "cpu0-supply = <&vdd_dvfs>;" does just provide the name of the power rail that supply the ca15 cluster.
>
> The postfix _dvfs is a little bit misleading in this case, I do agree.
>
> If you do no want voltage scaling, it is just a matter of keeping the same voltage in the OPP table. This is what I have done in the series I sent a while back.
>
When I tested, the voltage scaling is not disabled with only 
voltage setting of OPP table. The regulator side(da9210) must
also be set to the same voltage.
(When voltage scaling is activated, the environment will be unstable.)

I will post the fixed patch later.

> That being said, what is the exact voltage range supported by the CPU?
> AFAIR, with 28nm process some SoCs are able to scale down to 0.9v.
>

I do not have this information.