[v3,1/3] via-ide: Fix legacy mode emulation

The initial value for BARs were set in reset method for emulating
legacy mode at start but this does not work because PCI code resets
BARs after calling device reset method. Remove this ineffective
default to avoid confusion.

Instead move setting the BARs to a callback on writing the PCI config
regsiter that sets legacy mode (which firmwares needing this mode seem
to do). This does not fully emulate what the data sheet says (which is
not very clear on this) but it implements enough to allow both modes
as used by firmwares and guests on machines we emulate.

Signed-off-by: BALATON Zoltan <balaton@eik.bme.hu>
---
 hw/ide/via.c | 41 ++++++++++++++++++++++++++++++++++++-----
 1 file changed, 36 insertions(+), 5 deletions(-)

On 14/10/2023 20:37, BALATON Zoltan wrote:

> The initial value for BARs were set in reset method for emulating
> legacy mode at start but this does not work because PCI code resets
> BARs after calling device reset method. Remove this ineffective
> default to avoid confusion.
> 
> Instead move setting the BARs to a callback on writing the PCI config
> regsiter that sets legacy mode (which firmwares needing this mode seem
> to do). This does not fully emulate what the data sheet says (which is
> not very clear on this) but it implements enough to allow both modes
> as used by firmwares and guests on machines we emulate.
> 
> Signed-off-by: BALATON Zoltan <balaton@eik.bme.hu>
> ---
>   hw/ide/via.c | 41 ++++++++++++++++++++++++++++++++++++-----
>   1 file changed, 36 insertions(+), 5 deletions(-)
> 
> diff --git a/hw/ide/via.c b/hw/ide/via.c
> index fff23803a6..ca9a3b8f49 100644
> --- a/hw/ide/via.c
> +++ b/hw/ide/via.c
> @@ -132,11 +132,6 @@ static void via_ide_reset(DeviceState *dev)
>       pci_set_word(pci_conf + PCI_STATUS, PCI_STATUS_FAST_BACK |
>                    PCI_STATUS_DEVSEL_MEDIUM);
>   
> -    pci_set_long(pci_conf + PCI_BASE_ADDRESS_0, 0x000001f0);
> -    pci_set_long(pci_conf + PCI_BASE_ADDRESS_1, 0x000003f4);
> -    pci_set_long(pci_conf + PCI_BASE_ADDRESS_2, 0x00000170);
> -    pci_set_long(pci_conf + PCI_BASE_ADDRESS_3, 0x00000374);
> -    pci_set_long(pci_conf + PCI_BASE_ADDRESS_4, 0x0000cc01); /* BMIBA: 20-23h */
>       pci_set_long(pci_conf + PCI_INTERRUPT_LINE, 0x0000010e);
>   
>       /* IDE chip enable, IDE configuration 1/2, IDE FIFO Configuration*/
> @@ -159,6 +154,41 @@ static void via_ide_reset(DeviceState *dev)
>       pci_set_long(pci_conf + 0xc0, 0x00020001);
>   }
>   
> +static void via_ide_cfg_write(PCIDevice *pd, uint32_t addr,
> +                              uint32_t val, int len)
> +{
> +    pci_default_write_config(pd, addr, val, len);
> +    /*
> +     * Bits 0 and 2 of the PCI programming interface register are documented to
> +     * select between legacy and native mode for the two IDE channels. when the
> +     * guest selects legacy mode we reset the PCI BARs to legacy ports which is
> +     * their default value. We don't care about setting each channel separately
> +     * as no guest is known to do or need that. Also only do this when BARs are
> +     * unset when writing this register as logs from real hardware show that
> +     * setting legacy mode after BARs were set will still use ports set by BARs
> +     * not ISA ports (e.g. pegasos2 Linux does this after firmware set native
> +     * mode and programmed BARs). But if 0x8a is written righr after reset
> +     * without setting BARs then we want legacy ports (this is done by the
> +     * AmigaOne firmware). We can't set these in via_ide_reset() because PCI
> +     * code clears BARs after calling device reset method.
> +     */
> +    if (addr == PCI_CLASS_PROG && val == 0x8a &&
> +        pci_get_long(pd->config + PCI_BASE_ADDRESS_0) ==
> +        PCI_BASE_ADDRESS_SPACE_IO) {
> +        pci_set_long(pd->config + PCI_BASE_ADDRESS_0, 0x1f0
> +                     | PCI_BASE_ADDRESS_SPACE_IO);
> +        pci_set_long(pd->config + PCI_BASE_ADDRESS_1, 0x3f4
> +                     | PCI_BASE_ADDRESS_SPACE_IO);
> +        pci_set_long(pd->config + PCI_BASE_ADDRESS_2, 0x170
> +                     | PCI_BASE_ADDRESS_SPACE_IO);
> +        pci_set_long(pd->config + PCI_BASE_ADDRESS_3, 0x374
> +                     | PCI_BASE_ADDRESS_SPACE_IO);
> +        /* BMIBA: 20-23h */
> +        pci_set_long(pd->config + PCI_BASE_ADDRESS_4, 0xcc00
> +                     | PCI_BASE_ADDRESS_SPACE_IO);
> +    }
> +}
> +
>   static void via_ide_realize(PCIDevice *dev, Error **errp)
>   {
>       PCIIDEState *d = PCI_IDE(dev);
> @@ -221,6 +251,7 @@ static void via_ide_class_init(ObjectClass *klass, void *data)
>       /* Reason: only works as function of VIA southbridge */
>       dc->user_creatable = false;
>   
> +    k->config_write = via_ide_cfg_write;
>       k->realize = via_ide_realize;
>       k->exit = via_ide_exitfn;
>       k->vendor_id = PCI_VENDOR_ID_VIA;

Just posting the references to the v2 thread with the portio_list*() PoC explaining 
how this better models real hardware and how it forms the basis of future 
improvements so it can be found against v3 in Patchew:

https://lists.gnu.org/archive/html/qemu-devel/2023-10/msg04448.html
https://lists.gnu.org/archive/html/qemu-devel/2023-10/msg04449.html


ATB,

Mark.