[4.4-rc][PATCH] ARM: dts: am4372: fix clock source for arm twd and global timers
Tero Kristo
t-kristo at ti.com
Mon Nov 30 00:25:56 PST 2015
On 11/27/2015 09:44 PM, Grygorii Strashko wrote:
> ARM TWD and Global timer are clocked by PERIPHCLK which is MPU_CLK/2.
> But now they are clocked by dpll_mpu_m2_ck == MPU_CLK and, as result.
> Timekeeping core misbehaves. For example, execution of command
> "sleep 5" will take 10 sec instead of 5.
>
> Hence, fix it by adding mpu_periphclk ("fixed-factor-clock") and use
> it for clocking ARM TWD and Global timer (same way as on OMAP4).
>
> Cc: Tony Lindgren <tony at atomide.com>
> Cc: Felipe Balbi <balbi at ti.com>
> Cc: Tero Kristo <t-kristo at ti.com>
> Fixes:commit 8cbd4c2f6a99 ("arm: boot: dts: am4372: add ARM timers and SCU nodes")
> Signed-off-by: Grygorii Strashko <grygorii.strashko at ti.com>
> ---
> arch/arm/boot/dts/am4372.dtsi | 4 ++--
> arch/arm/boot/dts/am43xx-clocks.dtsi | 8 ++++++++
> 2 files changed, 10 insertions(+), 2 deletions(-)
>
> diff --git a/arch/arm/boot/dts/am4372.dtsi b/arch/arm/boot/dts/am4372.dtsi
> index d83ff9c..de8791a 100644
> --- a/arch/arm/boot/dts/am4372.dtsi
> +++ b/arch/arm/boot/dts/am4372.dtsi
> @@ -74,7 +74,7 @@
> reg = <0x48240200 0x100>;
> interrupts = <GIC_PPI 11 IRQ_TYPE_LEVEL_HIGH>;
> interrupt-parent = <&gic>;
> - clocks = <&dpll_mpu_m2_ck>;
> + clocks = <&mpu_periphclk>;
> };
>
> local_timer: timer at 48240600 {
> @@ -82,7 +82,7 @@
> reg = <0x48240600 0x100>;
> interrupts = <GIC_PPI 13 IRQ_TYPE_LEVEL_HIGH>;
> interrupt-parent = <&gic>;
> - clocks = <&dpll_mpu_m2_ck>;
> + clocks = <&mpu_periphclk>;
> };
>
> l2-cache-controller at 48242000 {
> diff --git a/arch/arm/boot/dts/am43xx-clocks.dtsi b/arch/arm/boot/dts/am43xx-clocks.dtsi
> index cc88728..2ff58b1 100644
> --- a/arch/arm/boot/dts/am43xx-clocks.dtsi
> +++ b/arch/arm/boot/dts/am43xx-clocks.dtsi
> @@ -259,6 +259,14 @@
> ti,invert-autoidle-bit;
> };
>
> + mpu_periphclk: mpu_periphclk {
> + #clock-cells = <0>;
> + compatible = "fixed-factor-clock";
> + clocks = <&dpll_mpu_ck>;
I don't think this is correct, ARM core is fed dpll_mpu_m2_ck, where the
divisor value can potentially differ from 1. If you feed this clock
directly from dpll_mpu_ck, you bypass this divisor.
Did you check what is the impact of cpufreq on the ARM TWD/timers?
-Tero
> + clock-mult = <1>;
> + clock-div = <2>;
> + };
> +
> dpll_ddr_ck: dpll_ddr_ck {
> #clock-cells = <0>;
> compatible = "ti,am3-dpll-clock";
>
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