Re: [PATCH 1/2] ARM: dts: imx6q-cm-fx6: fix the operation points

Hi Fabio,

thanks for your review!

On 06/12/2016 03:43 PM, Fabio Estevam wrote:

Hi Christopher,

On Sun, Jun 12, 2016 at 10:20 AM,  [off-list ref] wrote:

quoted

From: Valentin Raevsky <valentin-UTxiZqZC01RS1MOuV/RT9w@public.gmane.org>

Fix the cm-fx6 operation points. Remove settings for 1.2GHz.
The current ldo settings do not allow 1.2GHz cpu frequency.

Signed-off-by: Valentin Raevsky <valentin-UTxiZqZC01RS1MOuV/RT9w@public.gmane.org>
[christopher.spinrath-vA1bhqPz9FBZXbeN9DUtxg@public.gmane.org: rebased on upstream and adapted
 commit title]
Signed-off-by: Christopher Spinrath <redacted>
---
 arch/arm/boot/dts/imx6q-cm-fx6.dts | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/arch/arm/boot/dts/imx6q-cm-fx6.dts b/arch/arm/boot/dts/imx6q-cm-fx6.dts
index 6d8d5e9..c912d58 100644
--- a/arch/arm/boot/dts/imx6q-cm-fx6.dts
+++ b/arch/arm/boot/dts/imx6q-cm-fx6.dts

@@ -91,6 +91,23 @@
        };
 };

+&cpu0 {
+       operating-points = <
+               /* kHz  uV */
+               996000  1250000
+               852000  1250000
+               792000  1150000
+               396000  975000
+       >;
+       fsl,soc-operating-points = <
+               /* ARM kHz      SOC-PU uV */
+               996000          1250000
+               852000          1250000
+               792000          1175000
+               396000          1175000
+       >;

These operating points do not match the ones from imx6q.dtsi.

Indeed, the voltage for 792000kHz is not the same. Thanks for pointing
that out.

In order to avoid 1.2GHz operation we have
imx6q_opp_check_speed_grading() inside arch/arm/mach-imx/mach-imx6q.c.
This function checks if the mx6q is capable of running at 1.2GHz or
not, depending on the fuse reading and then it will skip the 1.2GHz
operating point if it detects it can't run at such frequency.

These operating points are defined at the SoC dtsi and we don't have
any board dts that define them locally like this patch proposes, so I
recommend we keep using the operating points from imx6q.dtsi.

Well, without this patch the SoC runs at 1.2GHz so it seems like the
fuse indicates that it is possible. But with a fair amount of IPs
enabled and high load the board becomes unstable (display
flickering/blanks, ethernet package drops, ...). I guess CompuLab
allowed 1.2GHz at first and then realized that it is a bad idea (at
least for some boards).

Is there any way to influence the fuse (e.g. from the
firmware/bootloader) or do you have another proposal on how to fix this
issue?

Cheers,
Christopher
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