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

Free up two registers by accessing SGPIO in two 16-byte chunks.

Browse Source 
The current code does reads and writes in two chunks: one of
6 words, followed by one of 2.

Instead, use two chunks of 4 words each. This takes the same number of
total cycles, but frees up two registers for other uses.

Note that we can't do things in one chunk, because we'd need eight
registers to hold the data, plus a ninth to hold the buffer pointer. The
ldm/stm instructions can only use the eight low registers, r0-r7.

So we have to use two chunks, and the most register-efficient way to do
that is to use two equal chunks.
This commit is contained in:
Martin Ling
2021-12-20 12:21:06 +00:00
parent c6362381d1
commit 9206a8b752
1 changed files with 12 additions and 12 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

24
firmware/hackrf_usb/sgpio_m0.s
View File

@ -179,17 +179,17 @@ loop:
direction_tx:
ldm buf_ptr!, {r0-r5} // 7
ldm buf_ptr!, {r0-r3} // 5
str r0, [sgpio_data, #SLICE0] // 8
str r1, [sgpio_data, #SLICE1] // 8
str r2, [sgpio_data, #SLICE2] // 8
str r3, [sgpio_data, #SLICE3] // 8
str r4, [sgpio_data, #SLICE4] // 8
str r5, [sgpio_data, #SLICE5] // 8
ldm buf_ptr!, {r0-r1} // 3
str r0, [sgpio_data, #SLICE6] // 8
str r1, [sgpio_data, #SLICE7] // 8
ldm buf_ptr!, {r0-r3} // 5
str r0, [sgpio_data, #SLICE4] // 8
str r1, [sgpio_data, #SLICE5] // 8
str r2, [sgpio_data, #SLICE6] // 8
str r3, [sgpio_data, #SLICE7] // 8
b done // 3
@ -199,13 +199,13 @@ direction_rx:
ldr r1, [sgpio_data, #SLICE1] // 10
ldr r2, [sgpio_data, #SLICE2] // 10
ldr r3, [sgpio_data, #SLICE3] // 10
ldr r4, [sgpio_data, #SLICE4] // 10
ldr r5, [sgpio_data, #SLICE5] // 10
stm buf_ptr!, {r0-r5} // 7
stm buf_ptr!, {r0-r3} // 5
ldr r0, [sgpio_data, #SLICE6] // 10
ldr r1, [sgpio_data, #SLICE7] // 10
stm buf_ptr!, {r0-r1} // 3
ldr r0, [sgpio_data, #SLICE4] // 10
ldr r1, [sgpio_data, #SLICE5] // 10
ldr r2, [sgpio_data, #SLICE6] // 10
ldr r3, [sgpio_data, #SLICE7] // 10
stm buf_ptr!, {r0-r3} // 5
done: