Sojus07/hackrf
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

Don't load M0 byte count from memory.

Browse Source 
This count is only written by the M0, so there's no need to reload it
when the current value is already retained in a register.

Removing this load saves two cycles in all code paths.
This commit is contained in:
Martin Ling
2021-12-24 14:50:22 +00:00
parent 4e205994e3
commit 0e99419be2
1 changed files with 7 additions and 7 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

14
firmware/hackrf_usb/sgpio_m0.s
View File

@ -66,10 +66,10 @@ shadow registers.
There are four key code paths, with the following worst-case timings:
RX, normal: 145 cycles
RX, overrun: 74 cycles
TX, normal: 134 cycles
TX, underrun: 141 cycles
RX, normal: 143 cycles
RX, overrun: 72 cycles
TX, normal: 132 cycles
TX, underrun: 139 cycles
Design
======
@ -161,6 +161,7 @@ buf_ptr .req r4
str zero, [state, #NUM_SHORTFALLS] // state.num_shortfalls = zero // 2
str zero, [state, #LONGEST_SHORTFALL] // state.longest_shortfall = zero // 2
mov shortfall_length, zero // shortfall_length = zero // 1
mov count, zero // count = zero // 1
.endm
.macro await_sgpio name
@ -196,7 +197,6 @@ buf_ptr .req r4
.macro update_buf_ptr
// Update the address of the buffer segment we want to write to / read from.
ldr count, [state, #M0_COUNT] // count = state.m0_count // 2
mov buf_ptr, buf_mask // buf_ptr = buf_mask // 1
and buf_ptr, count // buf_ptr &= count // 1
add buf_ptr, buf_base // buf_ptr += buf_base // 1
@ -311,7 +311,7 @@ tx_loop:
await_sgpio tx // await_sgpio() // 34
// Update buffer pointer.
update_buf_ptr // update_buf_ptr() // 5
update_buf_ptr // update_buf_ptr() // 3
// Load mode, and return to idle if requested.
mode .req r3
@ -392,7 +392,7 @@ rx_loop:
await_sgpio rx // await_sgpio() // 34
// Update buffer pointer.
update_buf_ptr // update_buf_ptr() // 5
update_buf_ptr // update_buf_ptr() // 3
// Load mode, and return to idle if requested.
mode .req r3