Re: [U-Boot] [PATCH] orion5x: optimize window size computation

-----Original Message----- From: u-boot-bounces@lists.denx.de [mailto:u-boot-bounces@lists.denx.de] On Behalf Of Albert Aribaud Sent: Tuesday, October 05, 2010 3:52 AM To: u-boot@lists.denx.de Subject: [U-Boot] [PATCH] orion5x: optimize window size computation

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.

This is wrong, you should be singed-off since you are posting and Chris can be contributor Or let him post the patch.

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;

BTW: How much this saves on size?

Regards.. Prafulla ..