linux-kernel - Re: [PATCH 2/3] ARM: sun8i: Add SMP support for the Allwinner A23

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Message-ID: <20150318102939.GP4638@lukather>
Date:	Wed, 18 Mar 2015 11:29:39 +0100
From:	Maxime Ripard <maxime.ripard@...e-electrons.com>
To:	Chen-Yu Tsai <wens@...e.org>
Cc:	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	linux-sunxi@...glegroups.com, Marc Zyngier <marc.zyngier@....com>
Subject: Re: [PATCH 2/3] ARM: sun8i: Add SMP support for the Allwinner A23

On Wed, Mar 18, 2015 at 11:24:01AM +0800, Chen-Yu Tsai wrote:
> The A23 is a dual Cortex-A7. Add the logic to use the IPs used to
> control the CPU configuration and the CPU power so that we can
> bring up secondary CPUs at boot.
> 
> Signed-off-by: Chen-Yu Tsai <wens@...e.org>
> ---
> 
> We can't use of_io_request_and_map() here, as it will conflict
> with PRCM, and leave us without a serial console.
> 
> I think a proper way to solve this would be a syscon device or
> something like the mfd-simple device posted by Arnd.
> 
> ---
>  Documentation/devicetree/bindings/arm/cpus.txt |  1 +
>  arch/arm/mach-sunxi/platsmp.c                  | 69 ++++++++++++++++++++++++++
>  2 files changed, 70 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/arm/cpus.txt b/Documentation/devicetree/bindings/arm/cpus.txt
> index 8b9e0a95de31..40202d85b132 100644
> --- a/Documentation/devicetree/bindings/arm/cpus.txt
> +++ b/Documentation/devicetree/bindings/arm/cpus.txt
> @@ -188,6 +188,7 @@ nodes to be present and contain the properties described below.
>  			# On ARM 32-bit systems this property is optional and
>  			  can be one of:
>  			    "allwinner,sun6i-a31"
> +			    "allwinner,sun8i-a23"
>  			    "arm,psci"
>  			    "brcm,brahma-b15"
>  			    "marvell,armada-375-smp"
> diff --git a/arch/arm/mach-sunxi/platsmp.c b/arch/arm/mach-sunxi/platsmp.c
> index 587b0468efcc..e8483ec79d67 100644
> --- a/arch/arm/mach-sunxi/platsmp.c
> +++ b/arch/arm/mach-sunxi/platsmp.c
> @@ -121,3 +121,72 @@ static struct smp_operations sun6i_smp_ops __initdata = {
>  	.smp_boot_secondary	= sun6i_smp_boot_secondary,
>  };
>  CPU_METHOD_OF_DECLARE(sun6i_a31_smp, "allwinner,sun6i-a31", &sun6i_smp_ops);
> +
> +static void __init sun8i_smp_prepare_cpus(unsigned int max_cpus)
> +{
> +	struct device_node *node;
> +
> +	node = of_find_compatible_node(NULL, NULL, "allwinner,sun8i-a23-prcm");
> +	if (!node) {
> +		pr_err("Missing A23 PRCM node in the device tree\n");
> +		return;
> +	}
> +
> +	prcm_membase = of_iomap(node, 0);
> +	if (!prcm_membase) {
> +		pr_err("Couldn't map A23 PRCM registers\n");
> +		return;
> +	}
> +
> +	node = of_find_compatible_node(NULL, NULL,
> +				       "allwinner,sun8i-a23-cpuconfig");
> +	if (!node) {
> +		pr_err("Missing A23 CPU config node in the device tree\n");
> +		return;
> +	}
> +
> +	cpucfg_membase = of_iomap(node, 0);
> +	if (!cpucfg_membase)
> +		pr_err("Couldn't map A23 CPU config registers\n");
> +
> +}
> +
> +static int sun8i_smp_boot_secondary(unsigned int cpu,
> +				    struct task_struct *idle)
> +{
> +	u32 reg;
> +
> +	if (!(prcm_membase && cpucfg_membase))
> +		return -EFAULT;
> +
> +	spin_lock(&cpu_lock);
> +
> +	/* Set CPU boot address */
> +	writel(virt_to_phys(secondary_startup),
> +	       cpucfg_membase + CPUCFG_PRIVATE0_REG);

One question I couldn't find any answer to is that does the SMP bit is
set in secondary_startup?

I couldn't find where it was set, but it still looks like the right
thing to do, so I would expect the code to do that.

Thanks!
Maxime

-- 
Maxime Ripard, Free Electrons
Embedded Linux, Kernel and Android engineering
http://free-electrons.com

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