Work around a dcache issue by preventing the game from doing
something pointless.
The game's DVD read function writes 0x87654321 to the entire read
buffer and 0x12345678 to the last 4 bytes. It then calls DVDReadAsync()
and without waiting for the read to complete at all, it checks if the
last 4 bytes are still 0x12345678. If they are, then the game fails.
The check always passes on console because DVDReadAsync() calls
issueCommand(), which calls DCInvalidateRange(read_buffer) (dcbi).
Dolphin cannot emulate this without an extremely significant
performance hit.
This commit changes devices to always return IPCCommandResult rather
than just a return code for Open() and Close() in order to be able
to better emulate reply timing.
In hindsight, I should have considered we would want to emulate
timing when I cleaned up the device interface, but alas.
This rectifies that mistake.
There is code below that assumes the presence of those macros (by #undef'ing them), but none of the included headers provided them.
This fixes a build failure on OpenBSD where the undef'd macros _do_ get picked up later on in a compilation unit (through which include, I don't know), and thus shadow the Common::swap* functions.
tl;dr: This PR speedups dolphin on mobiles with the Mali GPU and ES 3.2
drivers by a factor of 10 by using the method with the biggest overhead.
Please keep care not to buy this shit!
The ARM driver team seems to care very well about their customers. But
bad luck, users and open source developers are *not* their customers. So
even device-independent feature requests are just ignored for *years*:
https://community.arm.com/graphics/f/discussions/4645/gl_ext_buffer_storage-support
The bad point, they neither implement any of the other common ways to
stream dynamic content in unextented GL:
- They just ignore the GL_MAP_UNSYNCHRONIZED_BIT flag
- They don't support on-device buffer updates and just stall with
glBufferSubData
It seems like no benchmark is using any dynamic content - and like no
customer cares about anything but benchmarks, or users...
We have a flag to disable the glBufferSubData way, this PR adds the flag
to also disable the unsychronized mapping way. The second one is
available since their ES 3.2 update, but slow as hell.
So how to continue? The last remaining technical way to stream dynamic
content at all is to alloc a new buffer per draw call with glBufferData.
This is very gross, but still a factor 10 speedup compared to stalling
the GPU. Small tests shows that you can expect another 3-5 times speedup
with EXT_buffer_data, so Mali would be on pair with Adreno here. So if
you have bought such a device unfortunately, please try to make noise on
your vendor forums/support and ask for this extension. If you are going
to buy a new mobile, I'd recormend to avoid *any* mobile with a Mali GPU
in it.
Léo Lam