linux-kernel - Re: [RFC 00/19] Add interconnect and devfreq support for i.MX8MQ

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Date:   Fri, 24 Sep 2021 12:20:26 +0200
From:   Martin Kepplinger <martin.kepplinger@...i.sm>
To:     abel.vesa@....com
Cc:     a.fatoum@...gutronix.de, adrian.hunter@...el.com,
        aisheng.dong@....com, catalin.marinas@....com,
        cw00.choi@...sung.com, devicetree@...r.kernel.org,
        djakov@...nel.org, festevam@...il.com, kernel@...gutronix.de,
        kyungmin.park@...sung.com, linux-arm-kernel@...ts.infradead.org,
        linux-imx@....com, linux-kernel@...r.kernel.org,
        linux-pm@...r.kernel.org, linux-serial@...r.kernel.org,
        myungjoo.ham@...sung.com, robh@...nel.org, s.hauer@...gutronix.de,
        shawnguo@...nel.org, ulf.hansson@...aro.org, will.deacon@....com,
        Martin Kepplinger <martin.kepplinger@...i.sm>
Subject: Re: [RFC 00/19] Add interconnect and devfreq support for i.MX8MQ

hi Abel,

thank you for the update (this is actually v2 of this RFC right?)!

all in all this runs fine on the imx8mq (Librem 5 and devkit) I use. For all
the pl301 nodes I'm not yet sure what I can actually test / switch frequencies.

But I still have one problem: lcdif/mxfb already has the interconnect dram
DT property and I use the following call to request bandwidth:
https://source.puri.sm/martin.kepplinger/linux-next/-/commit/d690e4c021293f938eb2253607f92f5a64f15688
(mainlining this is on our todo list).

With your patchset, I get:

[    0.792960] genirq: Flags mismatch irq 30. 00000004 (mxsfb-drm) vs. 00000004 (mxsfb-drm)
[    0.801143] mxsfb 30320000.lcd-controller: Failed to install IRQ handler
[    0.808058] mxsfb: probe of 30320000.lcd-controller failed with error -16

so the main devfreq user (mxsfb) is not there :) why?

and when I remove the interconnect property from the lcdif DT node, mxsfb
probes again, but of course it doesn't lower dram freq as needed.

Do I do the icc calls wrong in mxsfb despite it working without your
patchset, or may there be something wrong on your side that breaks
the mxsfb IRQ?

again thanks a lot for working on this! I'm always happy to test.

                          martin

---
 .../boot/dts/freescale/imx8mq-librem5.dtsi    | 20 -------------------
 1 file changed, 20 deletions(-)

diff --git a/arch/arm64/boot/dts/freescale/imx8mq-librem5.dtsi b/arch/arm64/boot/dts/freescale/imx8mq-librem5.dtsi
index 6fac6676f412..8496a90f23bf 100644
--- a/arch/arm64/boot/dts/freescale/imx8mq-librem5.dtsi
+++ b/arch/arm64/boot/dts/freescale/imx8mq-librem5.dtsi
@@ -381,26 +381,6 @@ &A53_3 {
 	cpu-supply = <&buck2_reg>;
 };

-&ddrc {
-	operating-points-v2 = <&ddrc_opp_table>;
-
-	ddrc_opp_table: ddrc-opp-table {
-		compatible = "operating-points-v2";
-
-		opp-25M {
-			opp-hz = /bits/ 64 <25000000>;
-		};
-
-		opp-100M {
-			opp-hz = /bits/ 64 <100000000>;
-		};
-
-		opp-800M {
-			opp-hz = /bits/ 64 <800000000>;
-		};
-	};
-};
-
 &dphy {
 	status = "okay";
 };
-- 
2.30.2