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Re: [PATCH v3 4/8] hw/isa/vt82c686: Implement PCI IRQ routing

From: BALATON Zoltan
Subject: Re: [PATCH v3 4/8] hw/isa/vt82c686: Implement PCI IRQ routing
Date: Mon, 27 Feb 2023 13:57:51 +0100 (CET) 
On Mon, 27 Feb 2023, BALATON Zoltan wrote:

On Mon, 27 Feb 2023, BALATON Zoltan wrote:

On Mon, 27 Feb 2023, Bernhard Beschow wrote:
Am 26. Februar 2023 23:33:20 UTC schrieb BALATON Zoltan <balaton@eik.bme.hu>: 
On Sun, 26 Feb 2023, Bernhard Beschow wrote:
Am 25. Februar 2023 18:11:49 UTC schrieb BALATON Zoltan <balaton@eik.bme.hu>: 
From: Bernhard Beschow <shentey@gmail.com>
The real VIA south bridges implement a PCI IRQ router which is configured 
by the BIOS or the OS. In order to respect these configurations, QEMU
needs to implement it as well.
Note: The implementation was taken from piix4_set_irq() in hw/isa/piix4. 

Signed-off-by: Bernhard Beschow <shentey@gmail.com>
[balaton: declare gpio inputs instead of changing pci bus irqs so it can 
be connected in board code; remove some empty lines]
Signed-off-by: BALATON Zoltan <balaton@eik.bme.hu>
Tested-by: Rene Engel <ReneEngel80@emailn.de>
---
hw/isa/vt82c686.c | 39 +++++++++++++++++++++++++++++++++++++++
1 file changed, 39 insertions(+)

diff --git a/hw/isa/vt82c686.c b/hw/isa/vt82c686.c
index 3f9bd0c04d..4025f9bcdc 100644
--- a/hw/isa/vt82c686.c
+++ b/hw/isa/vt82c686.c
@@ -604,6 +604,44 @@ static void via_isa_request_i8259_irq(void *opaque, int irq, int level) 
    qemu_set_irq(s->cpu_intr, level);
}

+static int via_isa_get_pci_irq(const ViaISAState *s, int irq_num)
+{
+    switch (irq_num) {
+    case 0:
+        return s->dev.config[0x55] >> 4;
+    case 1:
+        return s->dev.config[0x56] & 0xf;
+    case 2:
+        return s->dev.config[0x56] >> 4;
+    case 3:
+        return s->dev.config[0x57] >> 4;
+    }
+    return 0;
+}
+
+static void via_isa_set_pci_irq(void *opaque, int irq_num, int level)
+{
+    ViaISAState *s = opaque;
+    PCIBus *bus = pci_get_bus(&s->dev);
+    int pic_irq;
+
+ /* now we change the pic irq level according to the via irq mappings */ 
+    /* XXX: optimize */
+    pic_irq = via_isa_get_pci_irq(s, irq_num);
+    if (pic_irq < ISA_NUM_IRQS) {
+        int i, pic_level;
+
+ /* The pic level is the logical OR of all the PCI irqs mapped to it. */ 
+        pic_level = 0;
+        for (i = 0; i < PCI_NUM_PINS; i++) {
+            if (pic_irq == via_isa_get_pci_irq(s, i)) {
+                pic_level |= pci_bus_get_irq_level(bus, i);
+            }
+        }
+        qemu_set_irq(s->isa_irqs[pic_irq], pic_level);
+    }
+}
+
static void via_isa_realize(PCIDevice *d, Error **errp)
{
    ViaISAState *s = VIA_ISA(d);
@@ -614,6 +652,7 @@ static void via_isa_realize(PCIDevice *d, Error **errp) 
    int i;

    qdev_init_gpio_out(dev, &s->cpu_intr, 1);
+ qdev_init_gpio_in_named(dev, via_isa_set_pci_irq, "pirq", PCI_NUM_PINS);
This line is a Pegasos2 specific addition for fixing its IRQ handling. Since this code must also work with the Fuloong2e board we should aim for a minimal changeset here which renders this line out of scope.
Let's keep the two series separate since now I need to watch two series for comments. Please use Based-on: tag next time instead.
Well, it's not. It's part of the QDev model for VT8231 that allows it to be connected by boards so I think this belongs here otherwise this won't even compile because the function you've added would be unused and bail on -Werror. Let's not make this more difficult than it is. I'm OK with reasonable changes but what's your goal now? You can't get rid of this line as it's how QDev can model it. Either I have to call into this model or have to export these pins as gpios.
Exporting the pins is a separate aspect on top of implementing PCI IRQ routing. To make this clear and obvious this should be a dedicated patch. In case either patch has an issue this would also ease and therefore acellerate discussions.
How would you do that? Introduce via_isa_set_pci_irq() as unused in this patch then have a one line patch to add connecting it to gpio pins? That just makes no sense. This is not modeling the chip with QDev and then the boatd 

This is now modeling...
can connect it as appropriate modeling the board that the chip is in. So if fuloon2e needs to do that then it should. I'll check that as I was focusing 

fuloong2e
I've checked fuloong2e and it still works as before. PCI bus is handled by bonito on that board so your patch would actually break it. The VIA chip is a PCIDevice. You're not supposed to replace the interrupts of the bus it's connected to from this model as that should be done by the pci-host or the board. Therefore modeling the chip's PIRQ/PINT pins as gpios which is the QDev concept for that is right and your usage of pci_set_irq here is wrong.
Please stop breaking my series. I had a working and tested series (still have that on my pegasos2 branch in case we end up chosing that) which was changed but you to something that is now conceptually wrong but still works because of guests don't change firmware defaults to share PCI interrupts with internal functions just to fulfill your assumption that internal functions are PCI devices (which now I have proof that they don't conform to that PCI standard doc, look at the comment in the last patch about PCI Command register in via-ac97 and compare that with the chip datasheet) but OK if this allows simlpler code in QEMU and still works I can accept that but don't push ideas that are wrong. 

Regards,
BALATON Zoltan
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