[PATCHv2 for soc 4/4] arm: socfpga: Add SMP support for actual socfpga harware

[Dinh Nguyen]

Hi Pavel,

> -----Original Message-----
> From: ZY - pavel
> Sent: Saturday, February 02, 2013 1:24 PM
> To: Dinh Nguyen
> Cc: Russell King - ARM Linux; olof at lixom.net; linux-arm-
> kernel at lists.infradead.org; arnd at arndb.de
> Subject: Re: [PATCHv2 for soc 4/4] arm: socfpga: Add SMP support for
> actual socfpga harware
>
> Hi!
>
> > > > > I actually thought about that... but could not think of non-
> ugly way
> > > > > of doing that. I hope dts will normally be "right" for any
> production
> > > > > system...
> > > >
> > > > I think a panic is better just for the reason that if someone is
> > > > expecting SMP, but missed the warning message, and later finds
> out that
> > > > the secondary core never came up, it would save some debugging
> time.
> > > >
> > > > Since I have to send out a v3 from the 1st patch anyways, let me
> verify
> > > > that I can get the early warning.
> > >
> > > The choice is between a panic() at a point where the only way to
> find
> > > out is to throw in printascii() or a working printk, and ending up
> with
> > > an unbootable kernel, vs continuing the boot and having an almost
> > > working system which can be logged into and the messages viewed.
> > >
> > > If you have an application which relies on the second CPU coming
> up,
> > > why not have it verify that the second CPU came up (it's quite easy
> > > to do - there's POSIX standard libc calls to get the number of
> online
> > > CPUs).
> >
> > Point taken...thanks Russell.
>
> Well, I don't think we normally check dtbs for validity with
> user-helpful error messages, but it is relatively easy in this case.
>
> ---cut here---
>
> Continue booting with second core disabled if cpu1-start-addr is not
> present in .dtb.
>
> Signed-off-by: Pavel Machek <pavel at denx.de>
>
> diff --git a/arch/arm/mach-socfpga/platsmp.c b/arch/arm/mach-
> socfpga/platsmp.c
> index 81e0da0..90facdd 100644
> --- a/arch/arm/mach-socfpga/platsmp.c
> +++ b/arch/arm/mach-socfpga/platsmp.c
> @@ -82,6 +82,9 @@ static void __init socfpga_smp_init_cpus(void)
>               ncores = 1;
>       }
>  #endif
> +     if (!cpu1start_addr)
> +             ncores = 1;
> +

This will not work because of commit 5587164eea4aad88fcb79d9b21dc8f14fea598cd
I sent out a V3 series of this patch, CPU1 will simply fail to come online if
cpu1-start-addr is not defined.

Dinh

>       for (i = 0; i < ncores; i++)
>               set_cpu_possible(i, true);
>
> diff --git a/arch/arm/mach-socfpga/socfpga.c b/arch/arm/mach-
> socfpga/socfpga.c
> index 334c330..c3cd88b 100644
> --- a/arch/arm/mach-socfpga/socfpga.c
> +++ b/arch/arm/mach-socfpga/socfpga.c
> @@ -74,10 +74,9 @@ static void __init socfpga_sysmgr_init(void)
>
>       np = of_find_compatible_node(NULL, NULL, "altr,sys-mgr");
>
> -     if (of_property_read_u32(np, "cpu1-start-addr", (u32 *)
> &cpu1start_addr)) {
> -             early_printk("Need cpu1-start-addr in device tree.\n");
> -             panic("Need cpu1-start-addr in device tree.\n");
> -     }
> +     if (of_property_read_u32(np, "cpu1-start-addr", (u32 *)
> &cpu1start_addr))
> +             printk(KERN_ALERT "Need cpu1-start-addr in device tree for
> SMP operation.\n");
> +
>       sys_manager_base_addr = of_iomap(np, 0);
>
>       np = of_find_compatible_node(NULL, NULL, "altr,rst-mgr");
>
> --
> (english) http://www.livejournal.com/~pavelmachek
> (cesky, pictures)
> http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html


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