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DMA: Determine slice size based on whether pad is transmitting

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Plenty of games seem to suffer from this issue where they have
a linked list DMA going while polling the controller. Using a
too-large slice size will result in the serial timing being off,
and the game thinking the controller is disconnected. So we
don't hurt performance too much for the general case, we reduce
this to equal CPU and DMA time when the controller is
transferring, but otherwise leave it at the higher size.
This commit is contained in:
Connor McLaughlin
2021-01-06 00:00:56 +10:00
parent 98a4e59f52
commit 845cd37835
3 changed files with 39 additions and 8 deletions
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37
src/core/dma.cpp
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@ -9,6 +9,7 @@
#include "gpu.h"
#include "interrupt_controller.h"
#include "mdec.h"
#include "pad.h"
#include "spu.h"
#include "system.h"
#ifdef WITH_IMGUI
@ -253,6 +254,34 @@ void DMA::UpdateIRQ()
}
}
// Plenty of games seem to suffer from this issue where they have a linked list DMA going while polling the
// controller. Using a too-large slice size will result in the serial timing being off, and the game thinking
// the controller is disconnected. So we don't hurt performance too much for the general case, we reduce this
// to equal CPU and DMA time when the controller is transferring, but otherwise leave it at the higher size.
enum : u32
{
SLICE_SIZE_WHEN_TRANSMITTING_PAD = 100,
HALT_TICKS_WHEN_TRANSMITTING_PAD = 100
};
TickCount DMA::GetTransferSliceTicks() const
{
#ifdef _DEBUG
if (g_pad.IsTransmitting())
{
Log_DebugPrintf("DMA transfer while transmitting pad - using lower slice size of %u vs %u",
SLICE_SIZE_WHEN_TRANSMITTING_PAD, m_max_slice_ticks);
}
#endif
return g_pad.IsTransmitting() ? SLICE_SIZE_WHEN_TRANSMITTING_PAD : m_max_slice_ticks;
}
TickCount DMA::GetTransferHaltTicks() const
{
return g_pad.IsTransmitting() ? HALT_TICKS_WHEN_TRANSMITTING_PAD : m_halt_ticks;
}
bool DMA::TransferChannel(Channel channel)
{
ChannelState& cs = m_state[static_cast<u32>(channel)];
@ -294,7 +323,7 @@ bool DMA::TransferChannel(Channel channel)
current_address & ADDRESS_MASK);
u8* ram_pointer = Bus::g_ram;
TickCount remaining_ticks = m_max_slice_ticks;
TickCount remaining_ticks = GetTransferSliceTicks();
while (cs.request && remaining_ticks > 0)
{
u32 header;
@ -330,7 +359,7 @@ bool DMA::TransferChannel(Channel channel)
if (cs.request)
{
// stall the transfer for a bit if we ran for too long
HaltTransfer(m_halt_ticks);
HaltTransfer(GetTransferHaltTicks());
return false;
}
else
@ -350,7 +379,7 @@ bool DMA::TransferChannel(Channel channel)
const u32 block_size = cs.block_control.request.GetBlockSize();
u32 blocks_remaining = cs.block_control.request.GetBlockCount();
TickCount ticks_remaining = m_max_slice_ticks;
TickCount ticks_remaining = GetTransferSliceTicks();
if (copy_to_device)
{
@ -391,7 +420,7 @@ bool DMA::TransferChannel(Channel channel)
{
// we got halted
if (!m_unhalt_event->IsActive())
HaltTransfer(m_halt_ticks);
HaltTransfer(GetTransferHaltTicks());
return false;
}