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author | Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk> | 2021-11-18 18:18:34 +0000 |
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committer | Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk> | 2021-11-21 09:56:52 +0000 |
commit | c29cd47e82df0bc7385cdd49a158d838314daa9e (patch) | |
tree | e17b19d26b3694212bc4babee384ba119053e968 /hw/char | |
parent | 8627edfb3f1fca24a96a0954148885c3241c10f8 (diff) | |
download | qemu-c29cd47e82df0bc7385cdd49a158d838314daa9e.zip qemu-c29cd47e82df0bc7385cdd49a158d838314daa9e.tar.gz qemu-c29cd47e82df0bc7385cdd49a158d838314daa9e.tar.bz2 |
escc: always set STATUS_TXEMPTY in R_STATUS on device reset
The "Transmit Interrupts and Transmit Buffer Empty Bit" section of the ESCC
datasheet states the following about the STATUS_TXEMPTY bit: "After a hardware
reset (including a hardware reset by software), or a channel reset, this bit
is set to 1".
Update escc_reset() to set the STATUS_TXEMPTY bit in the R_STATUS register
on device reset as described which fixes a regression whereby the Sun PROM
checks this bit early on startup and gets stuck in an infinite loop if it is
not set.
Signed-off-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>
Message-Id: <20211118181835.18497-2-mark.cave-ayland@ilande.co.uk>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Diffstat (limited to 'hw/char')
-rw-r--r-- | hw/char/escc.c | 11 |
1 files changed, 11 insertions, 0 deletions
diff --git a/hw/char/escc.c b/hw/char/escc.c index 0fce4f6..a7d9050 100644 --- a/hw/char/escc.c +++ b/hw/char/escc.c @@ -354,6 +354,17 @@ static void escc_reset(DeviceState *d) cs->rregs[j] = 0; cs->wregs[j] = 0; } + + /* + * ...but there is an exception. The "Transmit Interrupts and Transmit + * Buffer Empty Bit" section on page 50 of the ESCC datasheet says of + * the STATUS_TXEMPTY bit in R_STATUS: "After a hardware reset + * (including a hardware reset by software), or a channel reset, this + * bit is set to 1". The Sun PROM checks this bit early on startup and + * gets stuck in an infinite loop if it is not set. + */ + cs->rregs[R_STATUS] |= STATUS_TXEMPTY; + escc_reset_chn(cs); } } |