linux-kernel - Re: [PATCH 1/2] ARM: uniphier: fix up cache ops broadcast of ACTLR

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Message-ID: <20160329100308.GW19428@n2100.arm.linux.org.uk>
Date:	Tue, 29 Mar 2016 11:03:09 +0100
From:	Russell King - ARM Linux <linux@....linux.org.uk>
To:	Masahiro Yamada <yamada.masahiro@...ionext.com>
Cc:	arm@...nel.org, linux-arm-kernel@...ts.infradead.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] ARM: uniphier: fix up cache ops broadcast of ACTLR

On Tue, Mar 29, 2016 at 10:38:23AM +0900, Masahiro Yamada wrote:
> The Boot ROM of the UniPhier ARMv7 SoCs sets ACTLR (Auxiliary Control
> Register) to different values for different secure states:
> 
> [1] Set ACTLR to 0x41 for Non-secure boot
> [2] Set ACTLR to 0x40 for Secure boot
> 
> [1] is okay, but [2] is a problem.  Because of commit 1b3a02eb4523
> ("ARMv7: Check whether the SMP/nAMP mode was already enabled"),
> if bit 6 (SMP bit) is already set, the kernel skips the ACTLR setting.
> In that case, bit 0 (FW bit) is never set, so cache ops is not
> broadcasted, causing a cache coherency problem.
> 
> To solve the problem, this commit sets the bit 0 of ACTLR if the bit 4
> has already been set.  This change is harmless for [1] because the
> Boot ROM has already set NSACR (Non-secure Access Control Register)
> bit 18 (NS_SMP bit) before switching to Non-secure state in order to
> allow write access to the ACTLR.

The test in proc-v7.S is too weak, we should probably tighten it to
prevent these kinds of problems, iow:

 arch/arm/mm/proc-v7.S | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/arch/arm/mm/proc-v7.S b/arch/arm/mm/proc-v7.S
index 0f8963a7e7d9..6fcaac8e200f 100644
--- a/arch/arm/mm/proc-v7.S
+++ b/arch/arm/mm/proc-v7.S
@@ -281,12 +281,12 @@ __v7_ca17mp_setup:
 	bl      v7_invalidate_l1
 	ldmia	r12, {r1-r6, lr}
 #ifdef CONFIG_SMP
+	orr	r10, r10, #(1 << 6)		@ Enable SMP/nAMP mode
 	ALT_SMP(mrc	p15, 0, r0, c1, c0, 1)
-	ALT_UP(mov	r0, #(1 << 6))		@ fake it for UP
-	tst	r0, #(1 << 6)			@ SMP/nAMP mode enabled?
-	orreq	r0, r0, #(1 << 6)		@ Enable SMP/nAMP mode
-	orreq	r0, r0, r10			@ Enable CPU-specific SMP bits
-	mcreq	p15, 0, r0, c1, c0, 1
+	ALT_UP(mov	r0, r10)		@ fake it for UP
+	orr	r10, r10, r0			@ Set required bits
+	teq	r10, r0				@ Were they already set?
+	mcrne	p15, 0, r10, c1, c0, 1		@ No, update register
 #endif
 	b	__v7_setup_cont
 


-- 
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