RE: [PATCH v2 1/5] ARM: omap4: Correct definition of do_wfi() forCONFIG_THUMB2_KERNEL

[Santosh Shilimkar <santosh.shilimkar@ti.com>]

> -----Original Message-----
> From: Dave Martin [mailto:dave.martin@linaro.org]
> Sent: Friday, February 04, 2011 4:28 PM
> To: Santosh Shilimkar
> Cc: Russell King - ARM Linux; linux-arm-kernel@lists.infradead.org;
> Tony Lindgren; Nicolas Pitre; linux-omap@vger.kernel.org; Jean
> Pihet-XID
> Subject: Re: [PATCH v2 1/5] ARM: omap4: Correct definition of
> do_wfi() forCONFIG_THUMB2_KERNEL
>
> On Thu, Feb 3, 2011 at 7:30 PM, Santosh Shilimkar
> <santosh.shilimkar@ti.com> wrote:
> >> -----Original Message-----
[....]

> >> We actually have this:
> >>
> >> #if __LINUX_ARM_ARCH__ >= 7 ||          \
> >>         (__LINUX_ARM_ARCH__ == 6 && defined(CONFIG_CPU_32v6K))
> >> #define sev()   __asm__ __volatile__ ("sev" : : : "memory")
> >> #define wfe()   __asm__ __volatile__ ("wfe" : : : "memory")
> >> #define wfi()   __asm__ __volatile__ ("wfi" : : : "memory")
> >> #endif
> >>
> >> in asm/system.h, so maybe it should be using wfe() from
> asm/system.h
> >> ?
> > I assume you mean wfi here.
> > The problem is, omap2plus build breaks because it builds
> > CPU_32v6 and CPU_32v7 as well which doesn't support the wfi
> > instruction. Hence I used opcode directly to keep build
> > working.
>
> I guess that's right, OMAP2 is ARM1136 and doesn't have the K
> extensions.
>
> Would it make sense to have the v6 MCR equivalent as an altetnative?
> Something like:
>
> #elseif __LINUX_ARM_ARCH__ >= 6
> #define wfi()   __asm__ __volatile__ ( \
>     "mov     r0, #0\n\t" \
>     "mcr     p15, 0, r0, c7, c0, 4\n\t" \
>     ::: "r0"
> )
> #endif
>
> This MCR is a mandatory part of the architecture for v6, but it's
> not
> mandatory for older processors.
>
That should do as well.

Regards,
Santosh
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