Build error: versatile express

[Dave.Martin@arm.com (Dave Martin)]

On Mon, Aug 12, 2013 at 12:55:23PM -0400, Nicolas Pitre wrote:
> On Mon, 12 Aug 2013, Dave Martin wrote:
> 
> > On Mon, Aug 12, 2013 at 11:28:04AM +0100, Russell King - ARM Linux wrote:
> > > arch/arm/mach-vexpress/tc2_pm.c: In function 'tc2_pm_down.clone.0':
> > > arch/arm/mach-vexpress/tc2_pm.c:200:1: error: fp cannot be used in asm here
> > > 
> > > This is caused by the assembly code in this file clobbering R11, which
> > > is incompatible with having CONFIG_FRAME_POINTER=y.
> > 
> > Is there any reason not to fix this just by pushing/popping r11 inside
> > the asm and removing it from the clobber list?
> 
> That's most likely the best fix.  What about this?

Were we replacing these instances with the macro, or is that still in
flight?

Anyway, if useful:

Reviewed-by: Dave Martin <Dave.Martin@arm.com>

Cheers
---Dave

> 
> ---- >8
> 
> From: Nicolas Pitre <nicolas.pitre@linaro.org>
> Date: Mon, 12 Aug 2013 12:47:13 -0400
> Subject: [PATCH] ARM: vexpress/MCPM: fix cache disable sequence when
>  CONFIG_FRAME_POINTER=y
> 
> If CONFIG_FRAME_POINTER=y we hget the following error:
> 
> arch/arm/mach-vexpress/tc2_pm.c: In function 'tc2_pm_down':
> arch/arm/mach-vexpress/tc2_pm.c:200:1: error: fp cannot be used in asm here
> 
> Let's fix that by explicitly preserving r11 on the stack and removing it
> from the clobber list.
> 
> Reported-by: Russell King <linux@arm.linux.org.uk>
> Signed-off-by: Nicolas Pitre <nico@linaro.org>
> 
> diff --git a/arch/arm/mach-vexpress/dcscb.c b/arch/arm/mach-vexpress/dcscb.c
> index 85fffa702f..3a6384c6c4 100644
> --- a/arch/arm/mach-vexpress/dcscb.c
> +++ b/arch/arm/mach-vexpress/dcscb.c
> @@ -144,8 +144,13 @@ static void dcscb_power_down(void)
>  		 * Let's do it in the safest possible way i.e. with
>  		 * no memory access within the following sequence
>  		 * including to the stack.
> +		 *
> +		 * Note: fp is preserved to the stack explicitly prior doing
> +		 * this since adding it to the clobber list is incompatible
> +		 * with having CONFIG_FRAME_POINTER=y.
>  		 */
>  		asm volatile(
> +		"str	fp, [sp, #-4]! \n\t"
>  		"mrc	p15, 0, r0, c1, c0, 0	@ get CR \n\t"
>  		"bic	r0, r0, #"__stringify(CR_C)" \n\t"
>  		"mcr	p15, 0, r0, c1, c0, 0	@ set CR \n\t"
> @@ -156,9 +161,10 @@ static void dcscb_power_down(void)
>  		"bic	r0, r0, #(1 << 6)	@ disable local coherency \n\t"
>  		"mcr	p15, 0, r0, c1, c0, 1	@ set AUXCR \n\t"
>  		"isb	\n\t"
> -		"dsb	"
> +		"dsb	\n\t"
> +		"ldr	fp, [sp], #4"
>  		: : : "r0","r1","r2","r3","r4","r5","r6","r7",
> -		      "r9","r10","r11","lr","memory");
> +		      "r9","r10","lr","memory");
>  
>  		/*
>  		 * This is a harmless no-op.  On platforms with a real
> @@ -182,6 +188,7 @@ static void dcscb_power_down(void)
>  		 * Let's do it in the safest possible way as above.
>  		 */
>  		asm volatile(
> +		"str	fp, [sp, #-4]! \n\t"
>  		"mrc	p15, 0, r0, c1, c0, 0	@ get CR \n\t"
>  		"bic	r0, r0, #"__stringify(CR_C)" \n\t"
>  		"mcr	p15, 0, r0, c1, c0, 0	@ set CR \n\t"
> @@ -192,9 +199,10 @@ static void dcscb_power_down(void)
>  		"bic	r0, r0, #(1 << 6)	@ disable local coherency \n\t"
>  		"mcr	p15, 0, r0, c1, c0, 1	@ set AUXCR \n\t"
>  		"isb	\n\t"
> -		"dsb	"
> +		"dsb	\n\t"
> +		"ldr	fp, [sp], #4"
>  		: : : "r0","r1","r2","r3","r4","r5","r6","r7",
> -		      "r9","r10","r11","lr","memory");
> +		      "r9","r10","lr","memory");
>  	}
>  
>  	__mcpm_cpu_down(cpu, cluster);
> diff --git a/arch/arm/mach-vexpress/tc2_pm.c b/arch/arm/mach-vexpress/tc2_pm.c
> index dfb55d45b6..9419b1550a 100644
> --- a/arch/arm/mach-vexpress/tc2_pm.c
> +++ b/arch/arm/mach-vexpress/tc2_pm.c
> @@ -139,8 +139,13 @@ static void tc2_pm_down(u64 residency)
>  		 * Let's do it in the safest possible way i.e. with
>  		 * no memory access within the following sequence
>  		 * including the stack.
> +		 *
> +		 * Note: fp is preserved to the stack explicitly prior doing
> +		 * this since adding it to the clobber list is incompatible
> +		 * with having CONFIG_FRAME_POINTER=y.
>  		 */
>  		asm volatile(
> +		"str	fp, [sp, #-4]! \n\t"
>  		"mrc	p15, 0, r0, c1, c0, 0	@ get CR \n\t"
>  		"bic	r0, r0, #"__stringify(CR_C)" \n\t"
>  		"mcr	p15, 0, r0, c1, c0, 0	@ set CR \n\t"
> @@ -151,9 +156,10 @@ static void tc2_pm_down(u64 residency)
>  		"bic	r0, r0, #(1 << 6)	@ disable local coherency \n\t"
>  		"mcr	p15, 0, r0, c1, c0, 1	@ set AUXCR \n\t"
>  		"isb	\n\t"
> -		"dsb	"
> +		"dsb	\n\t"
> +		"ldr	fp, [sp], #4"
>  		: : : "r0","r1","r2","r3","r4","r5","r6","r7",
> -		      "r9","r10","r11","lr","memory");
> +		      "r9","r10","lr","memory");
>  
>  		cci_disable_port_by_cpu(mpidr);
>  
> @@ -174,6 +180,7 @@ static void tc2_pm_down(u64 residency)
>  		 * Let's do it in the safest possible way as above.
>  		 */
>  		asm volatile(
> +		"str	fp, [sp, #-4]! \n\t"
>  		"mrc	p15, 0, r0, c1, c0, 0	@ get CR \n\t"
>  		"bic	r0, r0, #"__stringify(CR_C)" \n\t"
>  		"mcr	p15, 0, r0, c1, c0, 0	@ set CR \n\t"
> @@ -184,9 +191,10 @@ static void tc2_pm_down(u64 residency)
>  		"bic	r0, r0, #(1 << 6)	@ disable local coherency \n\t"
>  		"mcr	p15, 0, r0, c1, c0, 1	@ set AUXCR \n\t"
>  		"isb	\n\t"
> -		"dsb	"
> +		"dsb	\n\t"
> +		"ldr	fp, [sp], #4"
>  		: : : "r0","r1","r2","r3","r4","r5","r6","r7",
> -		      "r9","r10","r11","lr","memory");
> +		      "r9","r10","lr","memory");
>  	}
>  
>  	__mcpm_cpu_down(cpu, cluster);
> 
> 
> > 
> > Since there are no "m" constraints or similar, there should be no
> > implicit references to fp or sp inside the asm which would be disrupted
> > by that.
> > 
> > We could #ifdef it on CONFIG_FRAME_POINTER, but that probably just
> > uglifies the code for no real benefit.
> > 
> > 
> > FRAME_POINTER depends on !THUMB2_KERNEL, so we shouldn't hit the same
> > issue with r7 in Thumb-2.
> > 
> > Cheers
> > ---Dave
> > 
> 
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