This is a note to let you know that I've just added the patch titled
ARM: dts: lan966x: fix sys_clk frequency
to the 5.18-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
arm-dts-lan966x-fix-sys_clk-frequency.patch
and it can be found in the queue-5.18 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From ef0324b6415db6742bd632dc0dfbb8fbc111473b Mon Sep 17 00:00:00 2001
From: Michael Walle <michael@xxxxxxxx>
Date: Sat, 26 Mar 2022 20:40:28 +0100
Subject: ARM: dts: lan966x: fix sys_clk frequency
From: Michael Walle <michael@xxxxxxxx>
commit ef0324b6415db6742bd632dc0dfbb8fbc111473b upstream.
The sys_clk frequency is 165.625MHz. The register reference of the
Generic Clock controller lists the CPU clock as 600MHz, the DDR clock as
300MHz and the SYS clock as 162.5MHz. This is wrong. It was first
noticed during the fan driver development and it was measured and
verified via the CLK_MON output of the SoC which can be configured to
output sys_clk/64.
The core PLL settings (which drives the SYS clock) seems to be as
follows:
DIVF = 52
DIVQ = 3
DIVR = 1
With a refernce clock of 25MHz, this means we have a post divider clock
Fpfd = Fref / (DIVR + 1) = 25MHz / (1 + 1) = 12.5MHz
The resulting VCO frequency is then
Fvco = Fpfd * (DIVF + 1) * 2 = 12.5MHz * (52 + 1) * 2 = 1325MHz
And the output frequency is
Fout = Fvco / 2^DIVQ = 1325MHz / 2^3 = 165.625Mhz
This all adds up to the constrains of the PLL:
10MHz <= Fpfd <= 200MHz
20MHz <= Fout <= 1000MHz
1000MHz <= Fvco <= 2000MHz
Fixes: 290deaa10c50 ("ARM: dts: add DT for lan966 SoC and 2-port board pcb8291")
Signed-off-by: Michael Walle <michael@xxxxxxxx>
Reviewed-by: Kavyasree Kotagiri <kavyasree.kotagiri@xxxxxxxxxxxxx>
Signed-off-by: Claudiu Beznea <claudiu.beznea@xxxxxxxxxxxxx>
Link: https://lore.kernel.org/r/20220326194028.2945985-1-michael@xxxxxxxx
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
arch/arm/boot/dts/lan966x.dtsi | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/arch/arm/boot/dts/lan966x.dtsi b/arch/arm/boot/dts/lan966x.dtsi
index 3cb02fffe716..38e90a31d2dd 100644
--- a/arch/arm/boot/dts/lan966x.dtsi
+++ b/arch/arm/boot/dts/lan966x.dtsi
@@ -38,7 +38,7 @@ clocks {
sys_clk: sys_clk {
compatible = "fixed-clock";
#clock-cells = <0>;
- clock-frequency = <162500000>;
+ clock-frequency = <165625000>;
};
cpu_clk: cpu_clk {
--
2.37.1
Patches currently in stable-queue which might be from michael@xxxxxxxx are
queue-5.18/arm-dts-lan966x-fix-sys_clk-frequency.patch
