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[Qemu-devel] qemu serial: lost tx irqs (affectig FreeBSD's new uart(4) d
From: |
Juergen Lock |
Subject: |
[Qemu-devel] qemu serial: lost tx irqs (affectig FreeBSD's new uart(4) driver) |
Date: |
Fri, 11 Sep 2009 23:35:08 +0200 |
User-agent: |
Mutt/1.5.20 (2009-06-14) |
Hi!
I got a report of FreeBSD guest's new uart(4) driver misbehaving in
qemu again(?) (output stopping for no apparent reason), and now found
out the problem is tx irqs (UART_IIR_THRI) are getting lost because
serial_update_irq() checks for the rx condtion,
... if ((s->ier & UART_IER_RDI) && (s->lsr & UART_LSR_DR))
first before checking for the tx irq condition,
... if ((s->ier & UART_IER_THRI) && s->thr_ipending)
which at least in this case (FreeBSD 8 guest after doing
set console="comconsole"
at the loader prompt or when simply echo'ing text to /dev/ttyu0
or typing to the serial port from cu(1) on a `regular' vga console)
causes the second condition (.. && s->thr_ipending) to be never
reached anymore, or only after a very long delay. Moving that
condition up so it is checked first like this,
Index: qemu/hw/serial.c
@@ -189,7 +188,9 @@ static void serial_update_irq(SerialStat
{
uint8_t tmp_iir = UART_IIR_NO_INT;
- if ((s->ier & UART_IER_RLSI) && (s->lsr & UART_LSR_INT_ANY)) {
+ if ((s->ier & UART_IER_THRI) && s->thr_ipending) {
+ tmp_iir = UART_IIR_THRI;
+ } else if ((s->ier & UART_IER_RLSI) && (s->lsr & UART_LSR_INT_ANY)) {
tmp_iir = UART_IIR_RLSI;
} else if ((s->ier & UART_IER_RDI) && s->timeout_ipending) {
/* Note that(s->ier & UART_IER_RDI) can mask this interrupt,
@@ -202,8 +203,6 @@ static void serial_update_irq(SerialStat
} else if (s->recv_fifo.count >= s->recv_fifo.itl) {
tmp_iir = UART_IIR_RDI;
}
- } else if ((s->ier & UART_IER_THRI) && s->thr_ipending) {
- tmp_iir = UART_IIR_THRI;
} else if ((s->ier & UART_IER_MSI) && (s->msr & UART_MSR_ANY_DELTA)) {
tmp_iir = UART_IIR_MSI;
}
...fixes the issue for me, but I'm not 100% sure if this might cause
rx irqs to come (too?) late when a guest keeps sending while its
receiving at the same time. Anyone care to comment? :)
Thanx,
Juergen
- [Qemu-devel] qemu serial: lost tx irqs (affectig FreeBSD's new uart(4) driver),
Juergen Lock <=
- [Qemu-devel] Re: qemu serial: lost tx irqs (affectig FreeBSD's new uart(4) driver), Jan Kiszka, 2009/09/12
- [Qemu-devel] Re: qemu serial: lost tx irqs (affectig FreeBSD's new uart(4) driver), Juergen Lock, 2009/09/12
- [Qemu-devel] Re: qemu serial: lost tx irqs (affectig FreeBSD's new uart(4) driver), Jan Kiszka, 2009/09/12
- Re: [Qemu-devel] Re: qemu serial: lost tx irqs (affectig FreeBSD's new uart(4) driver), Stefano Stabellini, 2009/09/14
- Re: [Qemu-devel] Re: qemu serial: lost tx irqs (affectig FreeBSD's new uart(4) driver), Aurelien Jarno, 2009/09/16
- Re: [Qemu-devel] Re: qemu serial: lost tx irqs (affectig FreeBSD's new uart(4) driver), Juergen Lock, 2009/09/23
- Re: [Qemu-devel] Re: qemu serial: lost tx irqs (affectig FreeBSD's new uart(4) driver), Aurelien Jarno, 2009/09/24
- Re: [Qemu-devel] Re: qemu serial: lost tx irqs (affectig FreeBSD's new uart(4) driver), Juergen Lock, 2009/09/24
[Qemu-devel] Re: qemu serial: lost tx irqs (affectig FreeBSD's new uart(4) driver), Olivier Cochard-Labbé, 2009/09/12