[U-Boot-Users] [PATCH 2/8] SPARC: SPARC cfi-flash support for 64-bit reads
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 }
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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
participants (2)
-
Daniel Hellstrom -
Wolfgang Denk