[RFC 1/3] serial: Enable MSI capablity and option

[Atish Patra]

The seria-pci device doesn't support MSI. Enable the device to provide
MSI so that any platform with MSI support only can also use
this serial device. MSI can be enabled by enabling the newly introduced
device property. This will be disabled by default preserving the current
behavior of the seria-pci device.

Signed-off-by: Atish Patra <atishp@rivosinc.com>
---
 hw/char/serial-pci.c | 36 +++++++++++++++++++++++++++++++++---
 1 file changed, 33 insertions(+), 3 deletions(-)

diff --git a/hw/char/serial-pci.c b/hw/char/serial-pci.c
index 93d6f9924425..ca93c2ce2776 100644
--- a/hw/char/serial-pci.c
+++ b/hw/char/serial-pci.c
@@ -31,6 +31,7 @@
 #include "hw/char/serial.h"
 #include "hw/irq.h"
 #include "hw/pci/pci.h"
+#include "hw/pci/msi.h"
 #include "hw/qdev-properties.h"
 #include "migration/vmstate.h"
 #include "qom/object.h"
@@ -39,26 +40,54 @@ struct PCISerialState {
     PCIDevice dev;
     SerialState state;
     uint8_t prog_if;
+    bool msi_enabled;
 };
 
 #define TYPE_PCI_SERIAL "pci-serial"
 OBJECT_DECLARE_SIMPLE_TYPE(PCISerialState, PCI_SERIAL)
 
+
+static void msi_irq_handler(void *opaque, int irq_num, int level)
+{
+    PCIDevice *pci_dev = opaque;
+
+    assert(level == 0 || level == 1);
+
+    if (msi_enabled(pci_dev)) {
+        msi_notify(pci_dev, 0);
+    }
+}
+
 static void serial_pci_realize(PCIDevice *dev, Error **errp)
 {
     PCISerialState *pci = DO_UPCAST(PCISerialState, dev, dev);
     SerialState *s = &pci->state;
+    Error *err = NULL;
+    int ret;
 
     if (!qdev_realize(DEVICE(s), NULL, errp)) {
         return;
     }
 
     pci->dev.config[PCI_CLASS_PROG] = pci->prog_if;
-    pci->dev.config[PCI_INTERRUPT_PIN] = 0x01;
-    s->irq = pci_allocate_irq(&pci->dev);
-
+    if (pci->msi_enabled) {
+        pci->dev.config[PCI_INTERRUPT_PIN] = 0x00;
+        s->irq = qemu_allocate_irq(msi_irq_handler, &pci->dev, 100);
+    } else {
+        pci->dev.config[PCI_INTERRUPT_PIN] = 0x01;
+        s->irq = pci_allocate_irq(&pci->dev);
+    }
     memory_region_init_io(&s->io, OBJECT(pci), &serial_io_ops, s, "serial", 8);
     pci_register_bar(&pci->dev, 0, PCI_BASE_ADDRESS_SPACE_IO, &s->io);
+
+    if (!pci->msi_enabled) {
+        return;
+    }
+
+    ret = msi_init(&pci->dev, 0, 1, true, false, &err);
+    if (ret == -ENOTSUP) {
+        fprintf(stdout, "MSIX INIT FAILED\n");
+    }
 }
 
 static void serial_pci_exit(PCIDevice *dev)
@@ -83,6 +112,7 @@ static const VMStateDescription vmstate_pci_serial = {
 
 static Property serial_pci_properties[] = {
     DEFINE_PROP_UINT8("prog_if",  PCISerialState, prog_if, 0x02),
+    DEFINE_PROP_BOOL("msi",  PCISerialState, msi_enabled, false),
     DEFINE_PROP_END_OF_LIST(),
 };
 
-- 
2.25.1