linux-kernel - Re: [PATCH 15/19] ARM: mmp: add SMP support

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Date:   Fri, 16 Aug 2019 11:11:00 -0700
From:   Florian Fainelli <f.fainelli@...il.com>
To:     Lubomir Rintel <lkundrak@...sk>, Olof Johansson <olof@...om.net>
Cc:     Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Jason Cooper <jason@...edaemon.net>,
        Marc Zyngier <maz@...nel.org>,
        Kishon Vijay Abraham I <kishon@...com>,
        Russell King <linux@...linux.org.uk>,
        Michael Turquette <mturquette@...libre.com>,
        Stephen Boyd <sboyd@...nel.org>, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-clk@...r.kernel.org
Subject: Re: [PATCH 15/19] ARM: mmp: add SMP support

On 8/9/19 2:31 AM, Lubomir Rintel wrote:
> Used to bring up the second core on MMP3.
> 
> Signed-off-by: Lubomir Rintel <lkundrak@...sk>
> ---
>  arch/arm/mach-mmp/Makefile  |  3 +++
>  arch/arm/mach-mmp/platsmp.c | 32 ++++++++++++++++++++++++++++++++
>  2 files changed, 35 insertions(+)
>  create mode 100644 arch/arm/mach-mmp/platsmp.c
> 
> diff --git a/arch/arm/mach-mmp/Makefile b/arch/arm/mach-mmp/Makefile
> index 322c1c97dc900..7b3a7f979eece 100644
> --- a/arch/arm/mach-mmp/Makefile
> +++ b/arch/arm/mach-mmp/Makefile
> @@ -22,6 +22,9 @@ ifeq ($(CONFIG_PM),y)
>  obj-$(CONFIG_CPU_PXA910)	+= pm-pxa910.o
>  obj-$(CONFIG_CPU_MMP2)		+= pm-mmp2.o
>  endif
> +ifeq ($(CONFIG_SMP),y)
> +obj-$(CONFIG_MACH_MMP3_DT)	+= platsmp.o
> +endif
>  
>  # board support
>  obj-$(CONFIG_MACH_ASPENITE)	+= aspenite.o
> diff --git a/arch/arm/mach-mmp/platsmp.c b/arch/arm/mach-mmp/platsmp.c
> new file mode 100644
> index 0000000000000..255df640b5bc1
> --- /dev/null
> +++ b/arch/arm/mach-mmp/platsmp.c
> @@ -0,0 +1,32 @@
> +// SPDX-License-Identifier: GPL-2.0-or-later
> +/*
> + * Copyright (C) 2019 Lubomir Rintel <lkundrak@...sk>
> + */
> +#include <linux/io.h>
> +#include <asm/smp_scu.h>
> +#include <asm/smp.h>
> +#include "addr-map.h"
> +
> +#define SW_BRANCH_VIRT_ADDR	CIU_REG(0x24)
> +
> +static int mmp3_boot_secondary(unsigned int cpu, struct task_struct *idle)
> +{
> +	/*
> +	 * Apparently, the boot ROM on the second core spins on this
> +	 * register becoming non-zero and then jumps to the address written
> +	 * there. No IPIs involved.
> +	 */
> +	__raw_writel(virt_to_phys(secondary_startup), SW_BRANCH_VIRT_ADDR);

You would want to use __pa_symbol() here (which is equivalent, but will
avoid barfing on you with CONFIG_DEBUG_VIRTUAL).
-- 
Florian