diff options
Diffstat (limited to 'pk/ppe42/ppe42_timebase.S')
| -rw-r--r-- | pk/ppe42/ppe42_timebase.S | 60 |
1 files changed, 47 insertions, 13 deletions
diff --git a/pk/ppe42/ppe42_timebase.S b/pk/ppe42/ppe42_timebase.S index 16c59529..43d64bb4 100644 --- a/pk/ppe42/ppe42_timebase.S +++ b/pk/ppe42/ppe42_timebase.S @@ -23,7 +23,43 @@ pk_timebase_get(void); .global ppe42_tb_data .global_function pk_timebase_get -//Use the DEC for our timebase until we have a real timebase register (uses 9 instructions) +#ifdef APPCFG_USE_DEC_FOR_TIMEBASE + + /// Note that it is ok to use this function in a fast interrupt + /// context + .align 5 + .global_function pk_timebase32_get +pk_timebase32_get: + + //load the decrementer start time and change tag + lvd %r4, ppe42_tb_data@sda21(0) + + //load the lower 32 bits of the 64bit timebase accumulator + lwz %r3, ppe42_64bit_timebase+4@sda21(0) + + //load the current decrementer value + mfdec %r0 + + //load the change tag again (should already be in the cache) + lwz %r6, ppe42_tb_data+4@sda21(0) + + //loop until the change tag is the same (typically should be same) + cmplwbne %r5, %r6, pk_timebase32_get + + //calculate how much time has passed since the decrementer was started and store in r6 + subf %r5, %r0, %r4 + + //add the 32bit difference to our 32bit timebase accumulator + add %r3, %r5, %r3 + + blr + + +/// Use the DEC for our timebase until we have a real timebase register (uses +/// 9 instructions). +/// Note: It is not ok to use this function in a fast interrupt context due to +/// its use of r7 + .align 5 pk_timebase_get: //load the decrementer start time and change tag @@ -40,9 +76,7 @@ pk_timebase_get: lwz %r7, ppe42_tb_data+4@sda21(0) //loop until the change tag is the same - //cmplwbne %r6, %r7, pk_timebase_get - cmplw %r6, %r7 - bne pk_timebase_get + cmplwbne %r6, %r7, pk_timebase_get //calculate how much time has passed since the decrementer was started and store in r6 subf %r6, %r0, %r5 @@ -54,28 +88,28 @@ pk_timebase_get: blr //enable this once we have a local timebase register in the model -#if 0 +#else // use the local timebase register to keep more accurate time with just 6 instructions // in the common case and 7 otherwise. + .align 5 pk_timebase_get: - //load the timebase local 32bit register address - lwz r5, timebase_local_reg@sda21(0) - //load the 64bit timebase accumulator - lvd r3, ppe42_64bit_timebase@sda21(0) + lvd r3, ppe42_64bit_timebase@sda21(0) - //read the local timebase register - lwz r5, 0(r5) + //read the local timebase register (2 instructions) + _pk_timebase32_get r5, r5 //increment the upper 32 bits if the lower 32 bits have flipped cmplwbgt r5, r4, update_lower_32 - addi r3, 1 //update upper 32 + + //increment the upper 32 bits + addi r3, r3, 1 update_lower_32: //replace the lower 32bits with what we read from the local timebase register - mr r4, r6 + mr r4, r5 blr #endif |
