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arch-x86: Implement count latching with the PIT read back command.

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This command can trigger count latching for any of the PIT channels
together with a single command, and can also latch a status byte. The
status byte is not implemented here, but there is already functionality
for latching the count which this can use.

Change-Id: Ic2ad7c73d0c521fdd6fe5f62cb478c6718f3b90c
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/55283
Reviewed-by: Gabe Black <gabe.black@gmail.com>
Maintainer: Gabe Black <gabe.black@gmail.com>
Tested-by: kokoro <noreply+kokoro@google.com>
This commit is contained in:
Gabe Black
2022-01-09 17:54:38 -08:00
parent 3a19fa4d8d
commit 946edc794f
2 changed files with 28 additions and 4 deletions
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20
src/dev/intel_8254_timer.cc
View File

@@ -58,12 +58,24 @@ Intel8254Timer::writeControl(const CtrlReg data)
{
int sel = data.sel;
if (sel == ReadBackCommand)
panic("PITimer Read-Back Command is not implemented.\n");
if (sel == ReadBackCommand) {
ReadBackCommandVal rb_val = static_cast<uint8_t>(data);
if (data.rw == LatchCommand)
panic_if(!rb_val.status,
"Latching the PIT status byte is not implemented.");
if (!rb_val.count) {
for (auto &cnt: counter) {
if (bits((uint8_t)rb_val.select, cnt->index()))
cnt->latchCount();
}
}
return;
}
if (data.rw == LatchCommand) {
counter[sel]->latchCount();
else {
} else {
counter[sel]->setRW(data.rw);
counter[sel]->setMode(data.mode);
counter[sel]->setBCD(data.bcd);

12
src/dev/intel_8254_timer.hh
View File

@@ -53,6 +53,16 @@ class Intel8254Timer : public EventManager
Bitfield<0> bcd;
EndBitUnion(CtrlReg)
BitUnion8(ReadBackCommandVal)
Bitfield<4> status; // Active low.
Bitfield<5> count; // Active low.
SubBitUnion(select, 3, 1)
Bitfield<3> cnt2;
Bitfield<2> cnt1;
Bitfield<1> cnt0;
EndSubBitUnion(select)
EndBitUnion(ReadBackCommandVal)
enum SelectVal
{
SelectCounter0,
@@ -152,6 +162,8 @@ class Intel8254Timer : public EventManager
public:
Counter(Intel8254Timer *p, const std::string &name, unsigned int num);
unsigned int index() const { return num; }
/** Latch the current count (if one is not already latched) */
void latchCount();