[PATCH 4/6] arm/imx6q: add smp and cpu hotplug support

[Shawn Guo]

On Tue, Sep 06, 2011 at 08:53:07PM +0200, Arnd Bergmann wrote:
> On Tuesday 06 September 2011 17:58:38 Shawn Guo wrote:
> > It adds smp and cpu hotplug support for imx6q.
> > +static u32 twd_saved_regs[4];
> > +static int twd_irq;
> > +
> > +/*
> > + * Resuming from ARM Dormant/Shutdown mode, the boot procedure will
> > + * re-setup local timer for secondary cores.  For primary core, it
> > + * has to take care of itself with the following pair of functions
> > + * during suspend/resume.
> > + */
> > +void imx_local_timer_pre_suspend(void)
> > +{
> > +	twd_saved_regs[0] = __raw_readl(twd_base + TWD_TIMER_LOAD);
> > +	twd_saved_regs[1] = __raw_readl(twd_base + TWD_TIMER_COUNTER);
> > +	twd_saved_regs[2] = __raw_readl(twd_base + TWD_TIMER_CONTROL);
> > +	twd_saved_regs[3] = __raw_readl(twd_base + TWD_TIMER_INTSTAT);
> > +}
> > +
> > +void imx_local_timer_post_resume(void)
> > +{
> > +	__raw_writel(twd_saved_regs[0], twd_base + TWD_TIMER_LOAD);
> > +	__raw_writel(twd_saved_regs[1], twd_base + TWD_TIMER_COUNTER);
> > +	__raw_writel(twd_saved_regs[2], twd_base + TWD_TIMER_CONTROL);
> > +	__raw_writel(twd_saved_regs[3], twd_base + TWD_TIMER_INTSTAT);
> > +
> > +	gic_enable_ppi(twd_irq);
> > +}
> 
> readl_relaxed()?
> 
Ok.  You get the best judgement on this.

> > +extern void v7_secondary_startup(void);
> > +
> > +#define IMX_SCU_VIRT_BASE	0xf4a00000
> > +
> > +static void __iomem *scu_base = ((void __iomem *)(IMX_SCU_VIRT_BASE));
> 
> It's a little bit silly to have a variable for the base and then initialize
> it statically. Not sure what the best solution is here.
> 
I have to admit that this scu mapping code was cloned from highbank :)

> > +static struct map_desc scu_io_desc __initdata = {
> > +	.virtual	= IMX_SCU_VIRT_BASE,
> > +	.pfn		= 0, /* run-time */
> > +	.length		= SZ_4K,
> > +	.type		= MT_DEVICE,
> > +};
> > +
> > +void __init imx_scu_map_io(void)
> > +{
> > +	unsigned long base;
> > +
> > +	/* Get SCU base */
> > +	asm("mrc p15, 4, %0, c15, c0, 0" : "=r" (base));
> > +
> > +	scu_io_desc.pfn = __phys_to_pfn(base);
> > +	iotable_init(&scu_io_desc, 1);
> > +}
> 
> Maybe we can simply define a platform-independent where the SCU gets mapped?
> That would get rid of most of the platform specific SCU code, at least for
> those platforms that can reliably read the scu base.
> 
Yes, if we can find a virtual base working for all platforms.  The scu
virtual base needs to be available before dynamic mapping gets ready,
so it has to be static mapping.

> > +/*
> > + * Initialise the CPU possible map early - this describes the CPUs
> > + * which may be present or become present in the system.
> > + */
> > +void __init smp_init_cpus(void)
> > +{
> > +	int i, ncores;
> > +
> > +	ncores = scu_get_core_count(scu_base);
> > +
> > +	for (i = 0; i < ncores; i++)
> > +		set_cpu_possible(i, true);
> > +
> > +	set_smp_cross_call(gic_raise_softirq);
> > +}
> > +
> > +void imx_smp_prepare(void)
> > +{
> > +	scu_enable(scu_base);
> > +}
> > +
> > +void __init platform_smp_prepare_cpus(unsigned int max_cpus)
> > +{
> > +	imx_smp_prepare();
> > +}
> 
> Then these functions could also be moved into the smp_scu file as generic
> helpers that can be used by all similar platforms.
> 

-- 
Regards,
Shawn