linux-kernel - [PATCH 1/2] ARM: build ssi-fiq.S in ARM mode to prevent CONFIG_THUMB2

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Date:	Tue,  7 Aug 2012 17:45:13 -0500
From:	Matt Sealey <matt@...esi-usa.com>
To:	Linux ARM Kernel Mailing List 
	<linux-arm-kernel@...ts.infradead.org>
Cc:	Steev Klimaszewski <steev@...esi-usa.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Matt Sealey <matt@...esi-usa.com>,
	Shawn Guo <shawn.guo@...aro.org>,
	Dave Martin <dave.martin@...aro.org>,
	Anton Vorontsov <anton.vorontsov@...aro.org>,
	Mark Brown <broonie@...nsource.wolfsonmicro.com>,
	Sascha Hauer <kernel@...gutronix.de>
Subject: [PATCH 1/2] ARM: build ssi-fiq.S in ARM mode to prevent CONFIG_THUMB2_KERNEL build breakage

If i.MX SSI FIQ support is enabled then it is impossible to build a Thumb2
kernel image due to the code not being written with Thumb2 in mind (over-use
of registers). In order not to break Thumb2 kernels, compile this as ARM. All
the processors which require this support will run ARM code so there is no
problem at runtime in doing this, even if it does produce a strange mix of
code that may not be desired.

In theory this should only be needed on configs based on imx_v4_v5_defconfig
where CONFIG_THUMB2_KERNEL cannot be selected anyway since these SoCs do not
have ARM cores capable of running Thumb2 code. This also makes rewriting the
code as Thumb-compatible kind of redundant. But since one Eukrea board audio
driver needs it, and there is an i.MX51 CPU module for this board, it gets
pulled in for imx_v6_v7_defconfig too, making this a necessity.

Signed-off-by: Matt Sealey <matt@...esi-usa.com>
---
 arch/arm/plat-mxc/ssi-fiq.S |    1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/arm/plat-mxc/ssi-fiq.S b/arch/arm/plat-mxc/ssi-fiq.S
index 8397a2d..ac09af8 100644
--- a/arch/arm/plat-mxc/ssi-fiq.S
+++ b/arch/arm/plat-mxc/ssi-fiq.S
@@ -28,6 +28,7 @@
 #define SSI_SIER_RFF0_EN	(1 << 2)

 		.text
+		.arm
 		.global	imx_ssi_fiq_start
 		.global	imx_ssi_fiq_end
 		.global imx_ssi_fiq_base
-- 
1.7.9.5

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