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mac_via: workaround NetBSD ADB bus enumeration issue

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NetBSD assumes it can send its first ADB command after sending the ADB_BUSRESET
command in ADB_STATE_NEW without changing the state back to ADB_STATE_IDLE
first as detailed in the ADB protocol.

Add a workaround to detect this condition at the start of ADB enumeration
and send the next command written to SR after a ADB_BUSRESET onto the bus
regardless, even if we don't detect a state transition to ADB_STATE_NEW.

Signed-off-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>
Reviewed-by: Laurent Vivier <laurent@vivier.eu>
Message-ID: <20231004083806.757242-16-mark.cave-ayland@ilande.co.uk>
Signed-off-by: Laurent Vivier <laurent@vivier.eu>
This commit is contained in:
Mark Cave-Ayland 2023-10-04 09:38:01 +01:00 committed by Laurent Vivier
parent 366d27796c
commit 2006904938
2 changed files with 35 additions and 0 deletions
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34
hw/misc/mac_via.c
View File

@ -1001,6 +1001,8 @@ static void mos6522_q800_via1_write(void *opaque, hwaddr addr, uint64_t val,
{
MOS6522Q800VIA1State *v1s = MOS6522_Q800_VIA1(opaque);
MOS6522State *ms = MOS6522(v1s);
int oldstate, state;
int oldsr = ms->sr;
addr = (addr >> 9) & 0xf;
@ -1016,6 +1018,38 @@ static void mos6522_q800_via1_write(void *opaque, hwaddr addr, uint64_t val,
v1s->last_b = ms->b;
break;
case VIA_REG_SR:
{
/*
* NetBSD assumes it can send its first ADB command after sending
* the ADB_BUSRESET command in ADB_STATE_NEW without changing the
* state back to ADB_STATE_IDLE first as detailed in the ADB
* protocol.
*
* Add a workaround to detect this condition at the start of ADB
* enumeration and send the next command written to SR after a
* ADB_BUSRESET onto the bus regardless, even if we don't detect a
* state transition to ADB_STATE_NEW.
*
* Note that in my tests the NetBSD state machine takes one ADB
* operation to recover which means the probe for an ADB device at
* address 1 always fails. However since the first device is at
* address 2 then this will work fine, without having to come up
* with a more complicated and invasive solution.
*/
oldstate = (v1s->last_b & VIA1B_vADB_StateMask) >>
VIA1B_vADB_StateShift;
state = (ms->b & VIA1B_vADB_StateMask) >> VIA1B_vADB_StateShift;
if (oldstate == ADB_STATE_NEW && state == ADB_STATE_NEW &&
(ms->acr & VIA1ACR_vShiftOut) &&
oldsr == 0 /* ADB_BUSRESET */) {
trace_via1_adb_netbsd_enum_hack();
adb_via_send(v1s, state, ms->sr);
}
}
break;
}
}

1
hw/misc/trace-events
View File

@ -271,6 +271,7 @@ via1_rtc_cmd_pram_sect_write(int sector, int offset, int addr, int value) "secto
via1_adb_send(const char *state, uint8_t data, const char *vadbint) "state %s data=0x%02x vADBInt=%s"
via1_adb_receive(const char *state, uint8_t data, const char *vadbint, int status, int index, int size) "state %s data=0x%02x vADBInt=%s status=0x%x index=%d size=%d"
via1_adb_poll(uint8_t data, const char *vadbint, int status, int index, int size) "data=0x%02x vADBInt=%s status=0x%x index=%d size=%d"
via1_adb_netbsd_enum_hack(void) "using NetBSD enum hack"
via1_auxmode(int mode) "setting auxmode to %d"
via1_timer_hack_state(int state) "setting timer_hack_state to %d"