[U-Boot] [PATCH] ARM: Rework and correct barrier definitions

[york sun]

On 08/01/2016 03:54 PM, Tom Rini wrote:
> As part of testing booting Linux kernels on Rockchip devices, it was
> discovered by Ziyuan Xu and Sandy Patterson that we had multiple and for
> some cases incomplete isb definitions.  This was causing a failure to
> boot of the Linux kernel.
>
> In order to solve this problem as well as cover any corner cases that we
> may also have had a number of changes are made in order to consolidate
> things.  First, <asm/barriers.h> now becomes the source of isb/dsb/dmb
> definitions.  This however introduces another complexity.  Due to
> needing to build SPL for 32bit tegra with -march=armv4 we need to borrow
> the __LINUX_ARM_ARCH__ logic from the Linux Kernel in a more complete
> form.  Move this from arch/arm/lib/Makefile to arch/arm/Makefile and add
> a comment about it.  Now that we can always know what the target CPU is
> capable off we can get always do the correct thing for the barrier.  The
> final part of this is that need to be consistent everywhere and call
> isb()/dsb()/dmb() and NOT call ISB/DSB/DMB in some cases and the
> function names in others.
>
> Reported-by: Ziyuan Xu <xzy.xu at rock-chips.com>
> Reported-by: Sandy Patterson <apatterson at sightlogix.com>
> Signed-off-by: Tom Rini <trini at konsulko.com>
> ---
> Good work on figuring this out guys.  Please test and ack this on your
> hardware as well.  I've given this a boot test on one of my platforms
> and built it for all ARM targets.
> ---

<snip>

>  arch/arm/include/asm/barriers.h            | 11 +++++++++--
>  arch/arm/include/asm/io.h                  |  4 ++--

<snip>

> diff --git a/arch/arm/include/asm/barriers.h b/arch/arm/include/asm/barriers.h
> index 37870f9..04784b7 100644
> --- a/arch/arm/include/asm/barriers.h
> +++ b/arch/arm/include/asm/barriers.h
> @@ -30,15 +30,22 @@
>
>  #endif /* !CONFIG_ARM64 */
>
> -#if defined(__ARM_ARCH_7A__) || defined(CONFIG_ARM64)
> +#if __LINUX_ARM_ARCH__ >= 7
>  #define ISB	asm volatile ("isb sy" : : : "memory")
>  #define DSB	asm volatile ("dsb sy" : : : "memory")
>  #define DMB	asm volatile ("dmb sy" : : : "memory")
> -#else
> +#elif __LINUX_ARM_ARCH__ == 6
>  #define ISB	CP15ISB
>  #define DSB	CP15DSB
>  #define DMB	CP15DMB
> +#else
> +#define ISB	asm volatile ("" : : : "memory")
> +#define DSB	CP15DSB
> +#define DMB	asm volatile ("" : : : "memory")
>  #endif
>
> +#define isb()	ISB
> +#define dsb()	DSB
> +#define dmb()	DMB
>  #endif	/* __ASSEMBLY__ */
>  #endif	/* __BARRIERS_H__ */
> diff --git a/arch/arm/include/asm/io.h b/arch/arm/include/asm/io.h
> index 6121f1d..5834f5b 100644
> --- a/arch/arm/include/asm/io.h
> +++ b/arch/arm/include/asm/io.h
> @@ -25,6 +25,7 @@
>  #include <linux/types.h>
>  #include <asm/byteorder.h>
>  #include <asm/memory.h>
> +#include <asm/barriers.h>
>  #if 0	/* XXX###XXX */
>  #include <asm/arch/hardware.h>
>  #endif	/* XXX###XXX */
> @@ -136,8 +137,7 @@ static inline void __raw_readsl(unsigned long addr, void *data, int longlen)
>   * TODO: The kernel offers some more advanced versions of barriers, it might
>   * have some advantages to use them instead of the simple one here.
>   */
> -#define mb()		asm volatile("dsb sy" : : : "memory")
> -#define dmb()		__asm__ __volatile__ ("" : : : "memory")
> +#define mb()		dsb()

Tom,

The replacement of dmb() broke ls2080ardb_nand, the spl boot part. I 
don't quite understand why dmb() was "", and why "dmb" is broken for spl.

York