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Date: Thu, 15 Dec 2016 16:52:58 -0800
From: Doug Anderson <dianders@...omium.org>
To: Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>
Cc: Javier Martinez Canillas <javier@....samsung.com>,
Arjun K V <arjun.kv@...sung.com>,
Krzysztof Kozlowski <krzk@...nel.org>,
Kukjin Kim <kgene@...nel.org>,
Rob Herring <robh+dt@...nel.org>,
Mark Rutland <mark.rutland@....com>,
Russell King <linux@...linux.org.uk>,
Andreas Faerber <afaerber@...e.de>,
Thomas Abraham <thomas.ab@...sung.com>,
Ben Gamari <ben@...rt-cactus.org>,
linux-samsung-soc <linux-samsung-soc@...r.kernel.org>,
"linux-arm-kernel@...ts.infradead.org"
<linux-arm-kernel@...ts.infradead.org>,
"linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
Alim <alim.akhtar@...sung.com>
Subject: Re: [PATCH] ARM: dts: Add missing CPU frequencies for Exynos5422/5800
Hi,
On Wed, Dec 14, 2016 at 5:28 AM, Bartlomiej Zolnierkiewicz
<b.zolnierkie@...sung.com> wrote:
>
> On Tuesday, December 13, 2016 04:18:05 PM Javier Martinez Canillas wrote:
>> Hello Bartlomiej,
>
> Hi,
>
>> 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@...omium.org>
>> > Cc: Javier Martinez Canillas <javier@....samsung.com>
>> > Cc: Andreas Faerber <afaerber@...e.de>
>> > Cc: Thomas Abraham <thomas.ab@...sung.com>
>> > Cc: Ben Gamari <ben@...rt-cactus.org>
>> > Signed-off-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.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@...0000000;
>> > + /delete-node/opp@...0000000;
>> > +};
>> > +
>> > +&cluster_a7_opp_table {
>> > + /delete-node/opp@...0000000;
>> > +};
>> > +
>>
>> 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.
>
> Ok, I will add these comments in the next patch revision.
>
>> > +&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@...0000000;
>> > +};
>> > +
>> > &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@...0000000 {
>> > + opp-hz = /bits/ 64 <2000000000>;
>> > + opp-microvolt = <1250000>;
>> > + clock-latency-ns = <140000>;
>> > + };
>> > + opp@...0000000 {
>> > + opp-hz = /bits/ 64 <1900000000>;
>> > + opp-microvolt = <1250000>;
>> > + clock-latency-ns = <140000>;
>> > + };
>> > opp@...0000000 {
>> > 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.
>
> I was not aware of this limitation and AFAIK mainline has currently
> no code to handle it. I also cannot find any code to handle this in
> Hardkernel's vendor kernel for Odroid-XU3 board.
>
> Do you know whether this problem exists also on Exynos5422/5800
> SoCs or only on Exynos5420 one? I see that ChromiumOS uses virtual
> regulator code also on Exynos5800 SoC based Peach Pi board but was
> the problem actually present on this board?
This was a long time ago and my memory is quite fuzzy. ...and I think
others have answered some of this already...
...but from my memory:
* This problem was said to exist on all Exynos 5420/5422/5800 SoCs.
* Samsung's original proposal included using the QoS subsystem to
enforce these constraints. I don't know where the Hardkernel source
is offhand, but you could check if that solution was used there? I
see one comment that links to these CLs:
https://chromium-review.googlesource.com/#/c/187420/
https://chromium-review.googlesource.com/#/c/187231/2
https://chromium-review.googlesource.com/#/c/184439/7
https://chromium-review.googlesource.com/#/c/184460/10
https://chromium-review.googlesource.com/#/c/186804/4
https://chromium-review.googlesource.com/#/c/186805/4
https://chromium-review.googlesource.com/#/c/186806/3
https://chromium-review.googlesource.com/#/c/186353/6
* Before using the voltage locker, we used an interrim solution of
bumping the INT frequency up to 500 MHz. See
<https://chromium-review.googlesource.com/#/c/187992/> and
<https://chromium-review.googlesource.com/#/c/187888/>. Perhaps this
is something that's happening upstream?
> [ I added Arjun to Cc:, maybe he can help in explaining this issue
> (unfortunately Inderpal's email is no longer working). ]
>
> Please also note that on Exynos5422/5800 SoCs the same ARM rail
> voltage is used for 1.9 GHz & 2.0 GHz OPPs as for the 1.8 GHz one.
> IOW if the problem exists it is already present in the mainline
> kernel.
Interesting. In the ChromeOS tree I see significantly higher voltages
needed... Note that one might naively look at
<https://chromium.googlesource.com/chromiumos/third_party/kernel/+/chromeos-3.8/drivers/cpufreq/exynos5420-cpufreq.c#178>.
1362500, /* L0 2100 */
1312500, /* L1 2000 */
..but, amazingly enough those voltages aren't used at all. Surprise!
I believe that the above numbers are actually not used and the ASV
numbers are used instead. See
<https://chromium.googlesource.com/chromiumos/third_party/kernel/+/chromeos-3.8/arch/arm/mach-exynos/include/mach/asv-exynos542x.h#452>
{ 2100000,
1350000, 1350000, 1350000, 1350000, 1350000,
1337500, 1325000, 1312500, 1300000, 1287500,
1275000, 1262500, 1250000, 1237500 },
I believe that interpretation there is: some bins of the CPU can run
at 2.1 GHz just fine at 1.25 V but others need up to 1.35V.
...so if you're running at 2.1 GHz at 1.25V then perhaps you're just
running on a CPU from a nice bin?
---
Anyway, I'm not setup at the moment to do a whole lot on exynos boards
(I'd have to go and dig some out and set them up again), so not sure
I'll be terribly useful in this discussion. ...but I can try to dig
up history, anyway.
-Doug
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