[U-Boot-Users] [PATCH 2/8] SPARC: SPARC cfi-flash support for 64-bit reads

[U-Boot-Users] [PATCH 2/8] SPARC: SPARC cfi-flash support for 64-bit reads

[Daniel Hellstrom]

For current SPARC architectures (LEON2 and LEON3) each read from the
FLASH must lead to a cache miss. This is because FLASH can not be set
non-cacheable since program code resides there, and alternatively disabling
cache is poor from performance view, or doing a cache flush between each 
read
is even poorer.

Forcing a cache miss on a SPARC is done by a special instruction "lda" -
load alternative space, the alternative space number (ASI) is processor
implementation spcific and can be found by including <asm/processor.h>.

SPARC has implemented __raw_readq, it reads 64-bit from any 32-bit address.

Best Regards,
Daniel Hellstrom


 drivers/mtd/cfi_flash.c |    4 ++++
 1 files changed, 4 insertions(+), 0 deletions(-)


diff --git a/drivers/mtd/cfi_flash.c b/drivers/mtd/cfi_flash.c
index 439c950..6fc6bc4 100644
--- a/drivers/mtd/cfi_flash.c
+++ b/drivers/mtd/cfi_flash.c
@@ -241,8 +241,12 @@ static u32 flash_read32(void *addr)
 
 static u64 flash_read64(void *addr)
 {
+#ifdef CONFIG_SPARC
+    return __raw_readq(addr);
+#else
     /* No architectures currently implement __raw_readq() */
     return *(volatile u64 *)addr;
+#endif
 }
 
 /*-----------------------------------------------------------------------

[U-Boot-Users] [PATCH 2/8] SPARC: SPARC cfi-flash support for 64-bit reads

[Wolfgang Denk]

In message <47D8F62A.2000108@gaisler.com> you wrote:
> For current SPARC architectures (LEON2 and LEON3) each read from the
> FLASH must lead to a cache miss. This is because FLASH can not be set
> non-cacheable since program code resides there, and alternatively disabling
> cache is poor from performance view, or doing a cache flush between each 
> read
> is even poorer.
> 
> Forcing a cache miss on a SPARC is done by a special instruction "lda" -
> load alternative space, the alternative space number (ASI) is processor
> implementation spcific and can be found by including <asm/processor.h>.
> 
> SPARC has implemented __raw_readq, it reads 64-bit from any 32-bit address.
> 
> Best Regards,
> Daniel Hellstrom
> 
> 
>  drivers/mtd/cfi_flash.c |    4 ++++
>  1 files changed, 4 insertions(+), 0 deletions(-)
> 
> 
> diff --git a/drivers/mtd/cfi_flash.c b/drivers/mtd/cfi_flash.c
> index 439c950..6fc6bc4 100644
> --- a/drivers/mtd/cfi_flash.c
> +++ b/drivers/mtd/cfi_flash.c
> @@ -241,8 +241,12 @@ static u32 flash_read32(void *addr)
>  
>  static u64 flash_read64(void *addr)
>  {
> +#ifdef CONFIG_SPARC
> +    return __raw_readq(addr);
> +#else
>      /* No architectures currently implement __raw_readq() */
>      return *(volatile u64 *)addr;
> +#endif
>  }

Instead of #ifdef'fing this code,  you  should  implement  a  private
(SPARC  specific)  version  of  flash_read64()  and probably make the
existing  one  "weak"  so  it  can  be  overwritten  by  such  custom
definitions.

Best regards,

Wolfgang Denk

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