X-Git-Url: http://git.mutantstargoat.com/user/nuclear/?p=rpikern;a=blobdiff_plain;f=doc%2Fnotes.md;h=5a372d8dc344fc148c63871e1c4fa8e1df4b2211;hp=0d4e804551d7cc0fdcf460bcd8f15fb9116108c6;hb=99bdc8838f189f79ba77bfbbf41d7f1b4839ce0f;hpb=6da291dc416a718164b5596aa16b1901f2770732

diff --git a/doc/notes.md b/doc/notes.md
index 0d4e804..5a372d8 100644
--- a/doc/notes.md
+++ b/doc/notes.md
@@ -1,6 +1,18 @@
 Raspberry Pi2 notes
 ===================
-The following is not all confirmed.
+Accessing different peripherals migh return results out of order. See bcm2835
+spec section 1.3. Use memory barriers as follows:
+ - place write barrier before the first write to a peripheral
+ - place read barrier after the last read of a peripheral
+
+Multiple accesses to the same peripheral in a row do not require barriers.
+
+Interrupt handlers should have a read barrier before their first read, and end
+with a write barrier.
+
+Cache clean and invalidate operations are also needed before the GPU can see our
+command buffers... see:
+https://github.com/rsta2/uspi/blob/38eaff4f715643a9/lib/synchronize.c
 
 Memory map
 ----------