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Re: [PATCH 3/3] ARM: imx: add SMP support for i.MX7D

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  Re: [PATCH 3/3] ARM: imx: add SMP support for i.MX7D Arnd Bergmann <arnd@arndb.de> - 2016-08-26 11:10 +0200
    RE: [PATCH 3/3] ARM: imx: add SMP support for i.MX7D Yongcai Huang <anson.huang@nxp.com> - 2016-08-26 12:50 +0200

#1470606 — Re: [PATCH 3/3] ARM: imx: add SMP support for i.MX7D

On Friday, August 26, 2016 7:12:51 PM CEST Anson Huang wrote:
> i.MX7D has 2 cortex-a7 ARM core, add support for
> booting up SMP kernel with 2 CPUs.
> 
> The existing i.MX SMP code is designed for i.MX6
> series SoCs which have cortex-a9 ARM core, but i.MX7D
> has 2 cortex-a7 ARM core, so we need to add runtime
> check for those differences between cortex-a9 and
> cortex-a7.
> 
> Signed-off-by: Anson Huang <Anson.Huang@nxp.com>
> 

Can't you just point i.MX7D to start from secondary_startup
rather than v7_secondary_startup?

 ENTRY(v7_secondary_startup)
+       .word   0xc070                  @ 0xc07 is cortex-a7 id
+       .word   0xfff0                  @ mask for core type
+

This looks like you are trying to execute instructions that are
actually data. Does this work?

On a side note, could you rename v7_secondary_startup to
imx6_secondary_startup? The name sounds overly generic
on a multiplatform kernel.

	Arnd

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#1470653

Best Regards!
Anson Huang



> -----Original Message-----
> From: Arnd Bergmann [mailto:arnd@arndb.de]
> Sent: 2016-08-26 4:59 PM
> To: Yongcai Huang <anson.huang@nxp.com>
> Cc: linux-arm-kernel@lists.infradead.org; devicetree@vger.kernel.org; linux-
> kernel@vger.kernel.org; shawnguo@kernel.org; kernel@pengutronix.de;
> Fabio Estevam <fabio.estevam@nxp.com>; robh+dt@kernel.org;
> mark.rutland@arm.com; linux@armlinux.org.uk
> Subject: Re: [PATCH 3/3] ARM: imx: add SMP support for i.MX7D
> 
> On Friday, August 26, 2016 7:12:51 PM CEST Anson Huang wrote:
> > i.MX7D has 2 cortex-a7 ARM core, add support for booting up SMP kernel
> > with 2 CPUs.
> >
> > The existing i.MX SMP code is designed for i.MX6 series SoCs which
> > have cortex-a9 ARM core, but i.MX7D has 2 cortex-a7 ARM core, so we
> > need to add runtime check for those differences between cortex-a9 and
> > cortex-a7.
> >
> > Signed-off-by: Anson Huang <Anson.Huang@nxp.com>
> >
> 
> Can't you just point i.MX7D to start from secondary_startup rather than
> v7_secondary_startup?
> 
>  ENTRY(v7_secondary_startup)
> +       .word   0xc070                  @ 0xc07 is cortex-a7 id
> +       .word   0xfff0                  @ mask for core type
> +
> 
> This looks like you are trying to execute instructions that are actually data. Does
> this work?
> 
> On a side note, could you rename v7_secondary_startup to
> imx6_secondary_startup? The name sounds overly generic on a multiplatform
> kernel.
> 
> 	Arnd


Thanks for review, yes, I made a mistake here, the data should put in another place,
but it accidently can work and boot up secondary CPU (see below the objdump),
 and also, I can just use  secondary_startup for i.MX7D. So I will
leave this file untouched, will verify the function next Mon and send out a V2 patch.

10 00000004 <v7_secondary_startup>:
 11    4:   0000c070        andeq   ip, r0, r0, ror r0
 12    8:   0000fff0        strdeq  pc, [r0], -r0

Anson.

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