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Diffstat (limited to 'arch/arm/cpu/arm926ejs/orion5x/cpu.c')
-rw-r--r--arch/arm/cpu/arm926ejs/orion5x/cpu.c32
1 files changed, 21 insertions, 11 deletions
diff --git a/arch/arm/cpu/arm926ejs/orion5x/cpu.c b/arch/arm/cpu/arm926ejs/orion5x/cpu.c
index c36d7bfef..1894b52fb 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.
+ * 64 KiB granularity (e.g., a value of 0x00FF specifies 256 = 16 MiB).
+ * NOTES:
+ * 1) A sizeval equal to 0x0 specifies 4 GiB.
+ * 2) A return value of 0x0 specifies 64 KiB.
*/
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;
}
/*