[Qemu-devel] [PATCH] hw/9118.c: Implement active-low interrupt support

[Peter Maydell]

The 9118 ethernet controller interrupt line is active low unless
the IRQ config register is programmed to set both the IRQ_POL
(polarity: active-high) and IRQ_TYPE (type: push-pull) bits:
implement support for inverting the irq output in other configurations.
This also requires that we support setting the bits in the first
place, and that we correctly preserve them across software reset.

Signed-off-by: Peter Maydell <address@hidden>
---
The motivation for this patch is actually an omap3 platform (overo)
which uses the active-low configuration; the platforms in QEMU
mainline which use it (vexpress and realview) both configure the
chip to active-high, which is why this bug hasn't come to light
before. I've tested that (a) my overo platform works with the
change and (b) it doesn't regress vexpress.

 hw/lan9118.c |   12 +++++++++---
 1 files changed, 9 insertions(+), 3 deletions(-)

diff --git a/hw/lan9118.c b/hw/lan9118.c
index 4c42fe9..3f3c05d 100644
--- a/hw/lan9118.c
+++ b/hw/lan9118.c
@@ -228,6 +228,12 @@ static void lan9118_update(lan9118_state *s)
     if ((s->irq_cfg & IRQ_EN) == 0) {
         level = 0;
     }
+    if ((s->irq_cfg & (IRQ_TYPE | IRQ_POL)) != (IRQ_TYPE | IRQ_POL)) {
+        /* Interrupt is active low unless we're configured as
+         * active-high polarity, push-pull type.
+         */
+        level = !level;
+    }
     qemu_set_irq(s->irq, level);
 }
 
@@ -294,8 +300,7 @@ static void phy_reset(lan9118_state *s)
 static void lan9118_reset(DeviceState *d)
 {
     lan9118_state *s = FROM_SYSBUS(lan9118_state, sysbus_from_qdev(d));
-
-    s->irq_cfg &= ~(IRQ_TYPE | IRQ_POL);
+    s->irq_cfg &= (IRQ_TYPE | IRQ_POL);
     s->int_sts = 0;
     s->int_en = 0;
     s->fifo_int = 0x48000000;
@@ -904,7 +909,8 @@ static void lan9118_writel(void *opaque, target_phys_addr_t 
offset,
     switch (offset) {
     case CSR_IRQ_CFG:
         /* TODO: Implement interrupt deassertion intervals.  */
-        s->irq_cfg = (s->irq_cfg & IRQ_INT) | (val & IRQ_EN);
+        val &= (IRQ_EN | IRQ_POL | IRQ_TYPE);
+        s->irq_cfg = (s->irq_cfg & IRQ_INT) | val;
         break;
     case CSR_INT_STS:
         s->int_sts &= ~val;
-- 
1.7.1