[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
[off-list ref] wrote:

quoted

-----Original Message-----
From: Russell King - ARM Linux [mailto:linux at arm.linux.org.uk]
Sent: Friday, February 04, 2011 12:38 AM
To: Santosh Shilimkar
Cc: Dave Martin; linux-arm-kernel at lists.infradead.org; Tony
Lindgren; Nicolas Pitre; linux-omap at vger.kernel.org; Jean Pihet-XID
Subject: Re: [PATCH v2 1/5] ARM: omap4: Correct definition of
do_wfi() forCONFIG_THUMB2_KERNEL

On Fri, Feb 04, 2011 at 12:09:34AM +0530, Santosh Shilimkar wrote:

quoted

quoted

-----Original Message-----
From: Dave Martin [mailto:dave.martin at linaro.org]
Sent: Thursday, February 03, 2011 11:33 PM
To: linux-arm-kernel at lists.infradead.org
Cc: Dave Martin; Tony Lindgren; Santosh Shilimkar; Jean Pihet;
linux-omap at vger.kernel.org; Nicolas Pitre
Subject: [PATCH v2 1/5] ARM: omap4: Correct definition of

do_wfi()

quoted

quoted

for CONFIG_THUMB2_KERNEL

For the Thumb-2 case, the "wfi" mnemonic is used, since in this
case the tools will necessarily be new enough to support it.

Signed-off-by: Dave Martin <redacted>

I guess, we discussed this patch in your previous post.
Acked-by: Santosh Shilimkar <redacted>

quoted

---
?arch/arm/mach-omap2/include/mach/omap4-common.h | ? ?5 +++++
?1 files changed, 5 insertions(+), 0 deletions(-)

diff --git a/arch/arm/mach-omap2/include/mach/omap4-common.h

b/arch/arm/mach-omap2/include/mach/omap4-common.h
index 5b0270b..68ce058 100644

--- a/arch/arm/mach-omap2/include/mach/omap4-common.h
+++ b/arch/arm/mach-omap2/include/mach/omap4-common.h

@@ -17,8 +17,13 @@

? * wfi used in low power code. Directly opcode is used instead
? * of instruction to avoid mulit-omap build break
? */
+#ifdef CONFIG_THUMB2_KERNEL
+#define do_wfi() ? ? ? ? ? ? ? ? \
+ ? ? ? ? __asm__ __volatile__ ("wfi" : : : "memory")
+#else
?#define do_wfi() ? ? ? ? ? ? ? ? \
? ? ? ? ? __asm__ __volatile__ (".word ? ?0xe320f003" : : :
"memory")
+#endif

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.

Cheers
---Dave