Subject: [PATCH] ARM: mvebu: convert secondary CPU clock sync to hotplug state

From: [email-masked] (Gregory CLEMENT)
Date: Wed, 27 Jun 2018 11:19:52 +0200

Hi Lucas,
 
 On lun., juin 18 2018, Lucas Stach <[email-masked]> wrote:

> The current call site in boot_secondary is causing sleep in invalid context
> warnings, as this part of the code is running with interrrupts disabled and
> some of the calls into the clock framework might sleep on a mutex.
>
> Convert the secondary CPU clock sync to a hotplug state, which allows to
> call it from a sleepable context.
>
> Signed-off-by: Lucas Stach <[email-masked]>

Tested on Aramda XP DB and applied on mvebu/arm

Thanks,

Gregory

> ---
>  arch/arm/mach-mvebu/platsmp.c | 49 ++++++++++++++++-------------------
>  include/linux/cpuhotplug.h    |  1 +
>  2 files changed, 24 insertions(+), 26 deletions(-)
>
> diff --git a/arch/arm/mach-mvebu/platsmp.c b/arch/arm/mach-mvebu/platsmp.c
> index 4ffbbd217e82..c130497dc6cc 100644
> --- a/arch/arm/mach-mvebu/platsmp.c
> +++ b/arch/arm/mach-mvebu/platsmp.c
> @@ -35,6 +35,8 @@
>  #define AXP_BOOTROM_BASE 0xfff00000
>  #define AXP_BOOTROM_SIZE 0x100000
>  
> +static struct clk *boot_cpu_clk;
> +
>  static struct clk *get_cpu_clk(int cpu)
>  {
>  	struct clk *cpu_clk;
> @@ -48,30 +50,6 @@ static struct clk *get_cpu_clk(int cpu)
>  	return cpu_clk;
>  }
>  
> -static void set_secondary_cpu_clock(unsigned int cpu)
> -{
> -	int thiscpu;
> -	unsigned long rate;
> -	struct clk *cpu_clk;
> -
> -	thiscpu = get_cpu();
> -
> -	cpu_clk = get_cpu_clk(thiscpu);
> -	if (!cpu_clk)
> -		goto out;
> -	clk_prepare_enable(cpu_clk);
> -	rate = clk_get_rate(cpu_clk);
> -
> -	cpu_clk = get_cpu_clk(cpu);
> -	if (!cpu_clk)
> -		goto out;
> -	clk_set_rate(cpu_clk, rate);
> -	clk_prepare_enable(cpu_clk);
> -
> -out:
> -	put_cpu();
> -}
> -
>  static int armada_xp_boot_secondary(unsigned int cpu, struct task_struct *idle)
>  {
>  	int ret, hw_cpu;
> @@ -79,7 +57,6 @@ static int armada_xp_boot_secondary(unsigned int cpu, struct task_struct *idle)
>  	pr_info("Booting CPU %d\n", cpu);
>  
>  	hw_cpu = cpu_logical_map(cpu);
> -	set_secondary_cpu_clock(hw_cpu);
>  	mvebu_pmsu_set_cpu_boot_addr(hw_cpu, armada_xp_secondary_startup);
>  
>  	/*
> @@ -122,6 +99,19 @@ static void __init armada_xp_smp_init_cpus(void)
>  		panic("Invalid number of CPUs in DT\n");
>  }
>  
> +static int armada_xp_sync_secondary_clk(unsigned int cpu)
> +{
> +	struct clk *cpu_clk = get_cpu_clk(cpu);
> +
> +	if (!cpu_clk || !boot_cpu_clk)
> +		return 0;
> +
> +	clk_prepare_enable(cpu_clk);
> +	clk_set_rate(cpu_clk, clk_get_rate(boot_cpu_clk));
> +
> +	return 0;
> +}
> +
>  static void __init armada_xp_smp_prepare_cpus(unsigned int max_cpus)
>  {
>  	struct device_node *node;
> @@ -131,6 +121,14 @@ static void __init armada_xp_smp_prepare_cpus(unsigned int max_cpus)
>  	flush_cache_all();
>  	set_cpu_coherent();
>  
> +	boot_cpu_clk = get_cpu_clk(smp_processor_id());
> +	if (boot_cpu_clk) {
> +		clk_prepare_enable(boot_cpu_clk);
> +		cpuhp_setup_state_nocalls(CPUHP_AP_ARM_MVEBU_SYNC_CLOCKS,
> +					  "arm/mvebu/sync_clocks:online",
> +					  armada_xp_sync_secondary_clk, NULL);
> +	}
> +
>  	/*
>  	 * In order to boot the secondary CPUs we need to ensure
>  	 * the bootROM is mapped at the correct address.
> @@ -223,7 +221,6 @@ static int mv98dx3236_boot_secondary(unsigned int cpu, struct task_struct *idle)
>  	int ret, hw_cpu;
>  
>  	hw_cpu = cpu_logical_map(cpu);
> -	set_secondary_cpu_clock(hw_cpu);
>  	mv98dx3236_resume_set_cpu_boot_addr(hw_cpu,
>  					    armada_xp_secondary_startup);
>  
> diff --git a/include/linux/cpuhotplug.h b/include/linux/cpuhotplug.h
> index 8796ba387152..fa54e5fbea38 100644
> --- a/include/linux/cpuhotplug.h
> +++ b/include/linux/cpuhotplug.h
> @@ -143,6 +143,7 @@ enum cpuhp_state {
>  	CPUHP_AP_SMPBOOT_THREADS,
>  	CPUHP_AP_X86_VDSO_VMA_ONLINE,
>  	CPUHP_AP_IRQ_AFFINITY_ONLINE,
> +	CPUHP_AP_ARM_MVEBU_SYNC_CLOCKS,
>  	CPUHP_AP_PERF_ONLINE,
>  	CPUHP_AP_PERF_X86_ONLINE,
>  	CPUHP_AP_PERF_X86_UNCORE_ONLINE,
> -- 
> 2.17.1
>

-- 
Gregory Clement, Bootlin (formerly Free Electrons)
Embedded Linux and Kernel engineering
http://bootlin.com