[PATCH 08/15] hw/intc: sifive_plic: Update "num-sources" property default value

[Bin Meng]

At present the default value of "num-sources" property is zero,
which does not make a lot of sense, as in sifive_plic_realize()
we see s->bitfield_words is calculated by:

  s->bitfield_words = (s->num_sources + 31) >> 5;

if the we don't configure "num-sources" property its default value
zero makes s->bitfield_words zero too, which isn't true because
interrupt source 0 still occupies one word.

Let's change the default value to 1 meaning that only interrupt
source 0 is supported by default and a sanity check in realize().

While we are here, add a comment to describe the exact meaning of
this property that the number should include interrupt source 0.
A wrong multi-line comment format is corrected too.

Signed-off-by: Bin Meng <bmeng@tinylab.org>
---

 hw/intc/sifive_plic.c | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/hw/intc/sifive_plic.c b/hw/intc/sifive_plic.c
index 5fd9a53569..2bd292410d 100644
--- a/hw/intc/sifive_plic.c
+++ b/hw/intc/sifive_plic.c
@@ -363,6 +363,11 @@ static void sifive_plic_realize(DeviceState *dev, Error 
**errp)
 
     parse_hart_config(s);
 
+    if (!s->num_sources) {
+        error_report("plic: invalid number of interrupt sources");
+        exit(1);
+    }
+
     s->bitfield_words = (s->num_sources + 31) >> 5;
     s->num_enables = s->bitfield_words * s->num_addrs;
     s->source_priority = g_new0(uint32_t, s->num_sources);
@@ -379,7 +384,8 @@ static void sifive_plic_realize(DeviceState *dev, Error 
**errp)
     s->m_external_irqs = g_malloc(sizeof(qemu_irq) * s->num_harts);
     qdev_init_gpio_out(dev, s->m_external_irqs, s->num_harts);
 
-    /* We can't allow the supervisor to control SEIP as this would allow the
+    /*
+     * We can't allow the supervisor to control SEIP as this would allow the
      * supervisor to clear a pending external interrupt which will result in
      * lost a interrupt in the case a PLIC is attached. The SEIP bit must be
      * hardware controlled when a PLIC is attached.
@@ -419,7 +425,8 @@ static const VMStateDescription vmstate_sifive_plic = {
 static Property sifive_plic_properties[] = {
     DEFINE_PROP_STRING("hart-config", SiFivePLICState, hart_config),
     DEFINE_PROP_UINT32("hartid-base", SiFivePLICState, hartid_base, 0),
-    DEFINE_PROP_UINT32("num-sources", SiFivePLICState, num_sources, 0),
+    /* number of interrupt sources including interrupt source 0 */
+    DEFINE_PROP_UINT32("num-sources", SiFivePLICState, num_sources, 1),
     DEFINE_PROP_UINT32("num-priorities", SiFivePLICState, num_priorities, 0),
     DEFINE_PROP_UINT32("priority-base", SiFivePLICState, priority_base, 0),
     DEFINE_PROP_UINT32("pending-base", SiFivePLICState, pending_base, 0),
-- 
2.34.1