Re: [PATCH] ARM: dts: Add missing CPU frequencies for Exynos5422/5800

[Javier Martinez Canillas <javier@osg.samsung.com>]

Hello Bartlomiej,

On 12/13/2016 01:52 PM, Bartlomiej Zolnierkiewicz wrote:
> Add missing 2000MHz & 1900MHz OPPs (for A15 cores) and 1400MHz OPP
> (for A7 cores).  Also update common Odroid-XU3 Lite/XU3/XU4 thermal
> cooling maps to account for new OPPs.
> 
> Since new OPPs are not available on all Exynos5422/5800 boards modify
> dts files for Odroid-XU3 Lite (limited to 1.8 GHz / 1.3 GHz) & Peach
> Pi (limited to 2.0 GHz / 1.3 GHz) accordingly.
> 
> Tested on Odroid-XU3 and XU3 Lite.
> 
> Cc: Doug Anderson <dianders@chromium.org>
> Cc: Javier Martinez Canillas <javier@osg.samsung.com>
> Cc: Andreas Faerber <afaerber@suse.de>
> Cc: Thomas Abraham <thomas.ab@samsung.com>
> Cc: Ben Gamari <ben@smart-cactus.org>
> Signed-off-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
> ---
>  arch/arm/boot/dts/exynos5422-odroidxu3-common.dtsi |   14 +++++++-------
>  arch/arm/boot/dts/exynos5422-odroidxu3-lite.dts    |   17 +++++++++++++++++
>  arch/arm/boot/dts/exynos5800-peach-pi.dts          |    4 ++++
>  arch/arm/boot/dts/exynos5800.dtsi                  |   15 +++++++++++++++
>  4 files changed, 43 insertions(+), 7 deletions(-)
> 
> Index: b/arch/arm/boot/dts/exynos5422-odroidxu3-common.dtsi
> ===================================================================
> --- a/arch/arm/boot/dts/exynos5422-odroidxu3-common.dtsi	2016-12-13 15:59:33.779763261 +0100
> +++ b/arch/arm/boot/dts/exynos5422-odroidxu3-common.dtsi	2016-12-13 15:59:33.775763261 +0100
> @@ -118,7 +118,7 @@
>  				/*
>  				 * When reaching cpu_alert3, reduce CPU
>  				 * by 2 steps. On Exynos5422/5800 that would
> -				 * be: 1600 MHz and 1100 MHz.
> +				 * (usually) be: 1800 MHz and 1200 MHz.
>  				 */
>  				map3 {
>  					trip = <&cpu_alert3>;
> @@ -131,16 +131,16 @@
>  
>  				/*
>  				 * When reaching cpu_alert4, reduce CPU
> -				 * further, down to 600 MHz (11 steps for big,
> -				 * 7 steps for LITTLE).
> +				 * further, down to 600 MHz (13 steps for big,
> +				 * 8 steps for LITTLE).
>  				 */
> -				map5 {
> +				cooling_map5: map5 {
>  					trip = <&cpu_alert4>;
> -					cooling-device = <&cpu0 3 7>;
> +					cooling-device = <&cpu0 3 8>;
>  				};
> -				map6 {
> +				cooling_map6: map6 {
>  					trip = <&cpu_alert4>;
> -					cooling-device = <&cpu4 3 11>;
> +					cooling-device = <&cpu4 3 13>;
>  				};
>  			};
>  		};
> Index: b/arch/arm/boot/dts/exynos5422-odroidxu3-lite.dts
> ===================================================================
> --- a/arch/arm/boot/dts/exynos5422-odroidxu3-lite.dts	2016-12-13 15:59:33.779763261 +0100
> +++ b/arch/arm/boot/dts/exynos5422-odroidxu3-lite.dts	2016-12-13 15:59:33.775763261 +0100
> @@ -21,6 +21,23 @@
>  	compatible = "hardkernel,odroid-xu3-lite", "samsung,exynos5800", "samsung,exynos5";
>  };
>  
> +&cluster_a15_opp_table {
> +	/delete-node/opp@2000000000;
> +	/delete-node/opp@1900000000;
> +};
> +
> +&cluster_a7_opp_table {
> +	/delete-node/opp@1400000000;
> +};
> +

I think that a comment in the DTS why these operating points aren't available
in this board will make more clear why the nodes are being deleted.

> +&cooling_map5 {
> +	cooling-device = <&cpu0 3 7>;
> +};
> +
> +&cooling_map6 {
> +	cooling-device = <&cpu4 3 11>;
> +};
> +
>  &pwm {
>  	/*
>  	 * PWM 0 -- fan
> Index: b/arch/arm/boot/dts/exynos5800-peach-pi.dts
> ===================================================================
> --- a/arch/arm/boot/dts/exynos5800-peach-pi.dts	2016-12-13 15:59:33.779763261 +0100
> +++ b/arch/arm/boot/dts/exynos5800-peach-pi.dts	2016-12-13 15:59:33.779763261 +0100
> @@ -146,6 +146,10 @@
>  	vdd-supply = <&ldo9_reg>;
>  };
>  
> +&cluster_a7_opp_table {
> +	/delete-property/opp@1400000000;
> +};
> +
>  &cpu0 {
>  	cpu-supply = <&buck2_reg>;
>  };
> Index: b/arch/arm/boot/dts/exynos5800.dtsi
> ===================================================================
> --- a/arch/arm/boot/dts/exynos5800.dtsi	2016-12-13 15:59:33.779763261 +0100
> +++ b/arch/arm/boot/dts/exynos5800.dtsi	2016-12-13 15:59:33.779763261 +0100
> @@ -24,6 +24,16 @@
>  };
>  
>  &cluster_a15_opp_table {
> +	opp@2000000000 {
> +		opp-hz = /bits/ 64 <2000000000>;
> +		opp-microvolt = <1250000>;
> +		clock-latency-ns = <140000>;
> +	};
> +	opp@1900000000 {
> +		opp-hz = /bits/ 64 <1900000000>;
> +		opp-microvolt = <1250000>;
> +		clock-latency-ns = <140000>;
> +	};
>  	opp@1700000000 {
>  		opp-microvolt = <1250000>;
>  	};
> @@ -85,6 +95,11 @@
>  };
>

AFAIK Thomas restricted the maximum OPP, because for A15 freqs > 1.8GHz the
INT rail would need to be scaled up as well since there's a maximum voltage
difference between the ARM and INT rails before the system becomes unstable:

http://lists.infradead.org/pipermail/linux-arm-kernel/2014-July/276766.html
https://lkml.org/lkml/2014/5/2/419

The ChromiumOS vendor tree uses a virtual regulator driver that makes sure
the maximum voltage skew is between a limit. But that never made to mainline:

https://chromium.googlesource.com/chromiumos/third_party/kernel/+/chromeos-3.8/arch/arm/boot/dts/exynos5420-peach-pit.dtsi#90
https://lkml.org/lkml/2014/4/29/28

Did that change and there's infrastructure in mainline now to cope with that?
If that's the case, I think it would be good to mention in the commit message.

Best regards,
-- 
Javier Martinez Canillas
Open Source Group
Samsung Research America