LADX: Fix getting old items over and over again in Bizhawk #2011
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zig-for
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ThePhar
added
the
is: bug/fix
wbsch
reviewed
Jul 23, 2023
| emu.frameadvance() | ||
| event.onmemoryexecute(on_vblank, 0x40, "ap_connector_vblank") | ||
|
|
||
| while true do |
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The emu.yield() loop should not be needed here, and is probably just burning cycles since there is now an event callback registered. Is there a reason for this I'm missing?
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It's needed on my machine and should have minimal perf impact
Berserker66
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Jul 27, 2023
FlySniper
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Nov 14, 2023
…goMW#2011) There was a bug that randomly after opening and closing the menu, some players on Bizhawk would get old items again. Tracking this down took multiple hours over the course of several weeks. The root cause turned out to be reading from the System Bus domain while an DMA copy was happening. Doing so is undefined behavior on GBC (though I'm sure some game relies on it). On Gambatte, you end up reading some garbage byte no matter what the read is (unsure what the providence of the byte is - some garbage, some register, the actual DMA data, who knows?). Normally, this isn't an issue, as Bizhawk callbacks only happen during vblank/halt, which is generally a state where we have valid WRAM to read from. However - a setting is being passed around the community for Bizhawk that changes the frame counter to go from "only when Vblank happens" to "whenever some number of audio samples have happened" which causes the bizhawk callbacks to happen....nearly whenever. Including during a DMA. You can tell this is happening if you print the `PC` register when reading memory - if it matches `FFXX` then you are executing in a routine in HRAM and likely doing a DMA. Additionally, the check items counter specifically is in WRAM Bank 1 which could be swapped out of - will have to keep an eye on this - generally LADX lives in Bank 1, but there are a few things that use the other banks (swap space for some objects??). This could be a problem on any platform - if we get more reports of bad items gets, that's probably why. Also, fixes some logging that was never getting reenabled.
kl3cks7r
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Dec 15, 2023
…goMW#2011) There was a bug that randomly after opening and closing the menu, some players on Bizhawk would get old items again. Tracking this down took multiple hours over the course of several weeks. The root cause turned out to be reading from the System Bus domain while an DMA copy was happening. Doing so is undefined behavior on GBC (though I'm sure some game relies on it). On Gambatte, you end up reading some garbage byte no matter what the read is (unsure what the providence of the byte is - some garbage, some register, the actual DMA data, who knows?). Normally, this isn't an issue, as Bizhawk callbacks only happen during vblank/halt, which is generally a state where we have valid WRAM to read from. However - a setting is being passed around the community for Bizhawk that changes the frame counter to go from "only when Vblank happens" to "whenever some number of audio samples have happened" which causes the bizhawk callbacks to happen....nearly whenever. Including during a DMA. You can tell this is happening if you print the `PC` register when reading memory - if it matches `FFXX` then you are executing in a routine in HRAM and likely doing a DMA. Additionally, the check items counter specifically is in WRAM Bank 1 which could be swapped out of - will have to keep an eye on this - generally LADX lives in Bank 1, but there are a few things that use the other banks (swap space for some objects??). This could be a problem on any platform - if we get more reports of bad items gets, that's probably why. Also, fixes some logging that was never getting reenabled.
Jouramie
pushed a commit
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that referenced
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Feb 28, 2024
…goMW#2011) There was a bug that randomly after opening and closing the menu, some players on Bizhawk would get old items again. Tracking this down took multiple hours over the course of several weeks. The root cause turned out to be reading from the System Bus domain while an DMA copy was happening. Doing so is undefined behavior on GBC (though I'm sure some game relies on it). On Gambatte, you end up reading some garbage byte no matter what the read is (unsure what the providence of the byte is - some garbage, some register, the actual DMA data, who knows?). Normally, this isn't an issue, as Bizhawk callbacks only happen during vblank/halt, which is generally a state where we have valid WRAM to read from. However - a setting is being passed around the community for Bizhawk that changes the frame counter to go from "only when Vblank happens" to "whenever some number of audio samples have happened" which causes the bizhawk callbacks to happen....nearly whenever. Including during a DMA. You can tell this is happening if you print the `PC` register when reading memory - if it matches `FFXX` then you are executing in a routine in HRAM and likely doing a DMA. Additionally, the check items counter specifically is in WRAM Bank 1 which could be swapped out of - will have to keep an eye on this - generally LADX lives in Bank 1, but there are a few things that use the other banks (swap space for some objects??). This could be a problem on any platform - if we get more reports of bad items gets, that's probably why. Also, fixes some logging that was never getting reenabled.
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What is this fixing or adding?
There was a bug that randomly after opening and closing the menu, some players on Bizhawk would get old items again. Tracking this down took multiple hours over the course of several weeks. The root cause turned out to be reading from the System Bus domain while an DMA copy was happening. Doing so is undefined behavior on GBC (though I'm sure some game relies on it). On Gambatte, you end up reading some garbage byte no matter what the read is (unsure what the providence of the byte is - some garbage, some register, the actual DMA data, who knows?). Normally, this isn't an issue, as Bizhawk callbacks only happen during vblank/halt, which is generally a state where we have valid WRAM to read from. However - a setting is being passed around the community for Bizhawk that changes the frame counter to go from "only when Vblank happens" to "whenever some number of audio samples have happened" which causes the bizhawk callbacks to happen....nearly whenever. Including during a DMA. You can tell this is happening if you print the
PCregister when reading memory - if it matchesFFXXthen you are executing in a routine in HRAM and likely doing a DMA.Additionally, the check items counter specifically is in WRAM Bank 1 which could be swapped out of - will have to keep an eye on this - generally LADX lives in Bank 1, but there are a few things that use the other banks (swap space for some objects??). This could be a problem on any platform - if we get more reports of bad items gets, that's probably why.
Also, fixes some logging that was never getting reenabled.
How was this tested?
Bizhawk 2.8, 2.9
If this makes graphical changes, please attach screenshots.
This shouldn't happen any more
