Signed-off-by: Chris Moore moore@free.fr ---
This is a simple optimization of the orion5x window size computation. This code was contributed by Chris Moore so I put his Signed-off-by rather than mine.
See http://www.mail-archive.com/u-boot@lists.denx.de/msg37075.html
arch/arm/cpu/arm926ejs/orion5x/cpu.c | 30 ++++++++++++++++++++---------- 1 files changed, 20 insertions(+), 10 deletions(-)
diff --git a/arch/arm/cpu/arm926ejs/orion5x/cpu.c b/arch/arm/cpu/arm926ejs/orion5x/cpu.c index c36d7bf..5c443fe 100644 --- a/arch/arm/cpu/arm926ejs/orion5x/cpu.c +++ b/arch/arm/cpu/arm926ejs/orion5x/cpu.c @@ -48,24 +48,34 @@ void reset_cpu(unsigned long ignored) }
/* - * Window Size + * Compute Window Size field value from size expressed in bytes * Used with the Base register to set the address window size and location. * Must be programmed from LSB to MSB as sequence of ones followed by * sequence of zeros. The number of ones specifies the size of the window in * 64 KByte granularity (e.g., a value of 0x00FF specifies 256 = 16 MByte). - * NOTE: A value of 0x0 specifies 64-KByte size. + * NOTES: + * 1) A sizeval equal to 0x0 specifies 4 TB. + * 2) A return value of 0x0 specifies 64 KB. */ unsigned int orion5x_winctrl_calcsize(unsigned int sizeval) { - int i; - unsigned int j = 0; - u32 val = sizeval >> 1; + /* + * Calculate the number of 64 KiB blocks needed minus one (rounding up). + * For sizeval > 0 this is equivalent to: + * sizeval = (u32) ceil((double) sizeval / 65536.0) - 1 + */ + sizeval = (sizeval - 1) >> 16;
- for (i = 0; val >= 0x10000; i++) { - j |= (1 << i); - val = val >> 1; - } - return 0x0000ffff & j; + /* + * Propagate 'one' bits to the right by 'oring' them. + * We need only treat bits 15-0. + */ + sizeval |= sizeval >> 1; /* 'Or' bit 15 onto bit 14 */ + sizeval |= sizeval >> 2; /* 'Or' bits 15-14 onto bits 13-12 */ + sizeval |= sizeval >> 4; /* 'Or' bits 15-12 onto bits 11-8 */ + sizeval |= sizeval >> 8; /* 'Or' bits 15-8 onto bits 7-0*/ + + return sizeval; }
/*