linux-kernel - Re: [PATCH 1/5] ARM: Add platform support for LSI AXM55xx SoC

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Date:	Thu, 24 Apr 2014 10:04:44 +0100
From:	Russell King - ARM Linux <linux@....linux.org.uk>
To:	Anders Berg <anders.berg@....com>
Cc:	arnd@...db.de, olof@...om.net, mturquette@...aro.org,
	mark.rutland@....com, dbaryshkov@...il.com,
	linus.walleij@...aro.org, linux-arm-kernel@...ts.infradead.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/5] ARM: Add platform support for LSI AXM55xx SoC

On Tue, Apr 15, 2014 at 02:06:10PM +0200, Anders Berg wrote:
> +	adr	r4, 2f
> +	ldmia	r4, {r5, r6}
> +	sub	r4, r4, r5
> +	add	r6, r6, r4
> +1:	ldr	r7, [r6]
> +	cmp	r7, r0
> +	wfene
> +	bne	1b
...
> +2:	.long	.
> +	.long	pen_release
> diff --git a/arch/arm/mach-axxia/platsmp.c b/arch/arm/mach-axxia/platsmp.c
...
> +/*
> + * Write pen_release in a way that is guaranteed to be visible to all
> + * observers, irrespective of whether they're taking part in coherency
> + * or not.  This is necessary for the hotplug code to work reliably.
> + */
> +static void write_pen_release(int val)
> +{
> +	pen_release = val;
> +	/* Make sure this store is visible to other CPUs */
> +	smp_wmb();
> +	__cpuc_flush_dcache_area((void *)&pen_release, sizeof(pen_release));
> +}

Do you /really/ need to do this pen_release thing on your platform?

> +static void __init axxia_smp_prepare_cpus(unsigned int max_cpus)
> +{
...
> +		/*
> +		 * Release all physical cpus when not in hyp mode since we
> +		 * might want to bring them online later.
> +		 *
> +		 * Also we need to get the execution into kernel code (it's
> +		 * currently executing in u-boot).  u-boot releases the cores
> +		 * from reset in hyp mode.
> +		 */
> +		if (!is_hyp_mode_available()) {
> +			if (cpu != 0) {
> +				u32 tmp = readl(syscon + 0x1010);
> +				writel(0xab, syscon + 0x1000);
> +				tmp &= ~(1 << cpu);
> +				writel(tmp, syscon + 0x1010);
> +			}

As this implies that you can control the release of each CPU from u-boot
individually.

-- 
FTTC broadband for 0.8mile line: now at 9.7Mbps down 460kbps up... slowly
improving, and getting towards what was expected from it.
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/