[PATCH v2] ARM: mvebu: Disable CPU Idle on Armada 38x

[Thomas Petazzoni]

Dear Gregory CLEMENT,

On Wed, 25 Feb 2015 19:30:50 +0100, Gregory CLEMENT wrote:
> On Armada 38x SoCs, under heavy I/O load, the system hangs when CPU
> Idle is enabled. Waiting for a solution to this issue, this patch
> disables the CPU Idle support for this SoC.
> 
> As CPU Hot plug support also uses some of the CPU Idle functions it is
> also affected by the same issue. This patch disables it also for the
> Armada 38x SoCs.
> 
> Signed-off-by: Gregory CLEMENT <gregory.clement at free-electrons.com>
> Cc: <stable at vger.kernel.org> # v3.17 +

Tested-by: Thomas Petazzoni <thomas.petazzoni at free-electrons.com>

I tested on Armada 38x, and indeed CPU hotplug is properly disabled,
and it doesn't prevent suspend/resume (not supported yet in mainline,
but hopefully soon to be supported).

Some minor comments below.

> diff --git a/arch/arm/mach-mvebu/pmsu.c b/arch/arm/mach-mvebu/pmsu.c
> index 8b9f5e202ccf..2145f192662f 100644
> --- a/arch/arm/mach-mvebu/pmsu.c
> +++ b/arch/arm/mach-mvebu/pmsu.c
> @@ -415,6 +415,9 @@ static __init int armada_38x_cpuidle_init(void)
>  	void __iomem *mpsoc_base;
>  	u32 reg;
>  
> +	pr_warn("CPU Idle is currently broken on Armada 38x: disabling");

Idle -> idle

> +	return 0;
> +
>  	np = of_find_compatible_node(NULL, NULL,
>  				     "marvell,armada-380-coherency-fabric");
>  	if (!np)
> @@ -469,13 +472,23 @@ static __init int armada_xp_cpuidle_init(void)
>  static int __init mvebu_v7_cpu_pm_init(void)
>  {
>  	struct device_node *np;
> -	int ret;
> +	int ret = 0;

Not clear why this change is needed.

>  
>  	np = of_find_matching_node(NULL, of_pmsu_table);
>  	if (!np)
>  		return 0;
>  	of_node_put(np);
>  
> +	/*
> +	 * Currently the CPU Idle support for Armada 38x is broken, as
> +	 * the CPU Hotplug uses some of the CPU Idle functions it is
> +	 * broken too, so let's disable it
> +	 */
> +	if (of_machine_is_compatible("marvell,armada380")) {
> +		cpu_hotplug_disable();
> +		pr_warn("CPU Hotplug support is currently broken on Armada 38x: disabling");

Hotplug -> hotplug.

Thanks,

Thomas
-- 
Thomas Petazzoni, CTO, Free Electrons
Embedded Linux, Kernel and Android engineering
http://free-electrons.com