Re: [Qemu-devel] [PATCH v2 1/3] lsi53c895a: hide 53c895a registers in 53c810

[Mark Cave-Ayland]

On 04/05/2019 22:02, Artyom Tarasenko wrote:

> AIX/PReP does access to the aliased IO registers of 53810.
> Implement aliasing to make the AIX driver work.
> 
> Signed-off-by: Artyom Tarasenko <address@hidden>
> ---
>  hw/scsi/lsi53c895a.c | 17 ++++++++++++++---
>  1 file changed, 14 insertions(+), 3 deletions(-)
> 
> diff --git a/hw/scsi/lsi53c895a.c b/hw/scsi/lsi53c895a.c
> index da7239d..6b95699 100644
> --- a/hw/scsi/lsi53c895a.c
> +++ b/hw/scsi/lsi53c895a.c
> @@ -2271,6 +2271,9 @@ static void lsi_scsi_realize(PCIDevice *dev, Error 
> **errp)
>      LSIState *s = LSI53C895A(dev);
>      DeviceState *d = DEVICE(dev);
>      uint8_t *pci_conf;
> +    uint64_t mmio_size;
> +    MemoryRegion *mr;
> +    uint16_t type = PCI_DEVICE_GET_CLASS(dev)->device_id;
>  
>      pci_conf = dev->config;
>  
> @@ -2279,13 +2282,21 @@ static void lsi_scsi_realize(PCIDevice *dev, Error 
> **errp)
>      /* Interrupt pin A */
>      pci_conf[PCI_INTERRUPT_PIN] = 0x01;
>  
> -    memory_region_init_io(&s->mmio_io, OBJECT(s), &lsi_mmio_ops, s,
> -                          "lsi-mmio", 0x400);
>      memory_region_init_io(&s->ram_io, OBJECT(s), &lsi_ram_ops, s,
>                            "lsi-ram", 0x2000);
>      memory_region_init_io(&s->io_io, OBJECT(s), &lsi_io_ops, s,
>                            "lsi-io", 256);
> -
> +    if (type == PCI_DEVICE_ID_LSI_53C895A) {
> +        mmio_size = 0x400;
> +    } else {
> +        mr = g_new(MemoryRegion, 1);

In general these days it's worth keeping the reference to the MemoryRegion 
within
LSIState since then its lifecycle is more clearly defined.

> +        memory_region_init_alias(mr, OBJECT(d), "lsi-io-alias", &s->io_io,
> +                                 0, 0x80);
> +        memory_region_add_subregion_overlap(&s->io_io, 0x80, mr, -1);
> +        mmio_size = 0x80;

This feels a little strange - is it possible to see from the datasheets that the
53C895A has 0x400 bytes MMIO whilst the 53C810 has 0x80 bytes MMIO? It's not 
clear to
me where the aliasing is happening.

> +    }
> +    memory_region_init_io(&s->mmio_io, OBJECT(s), &lsi_mmio_ops, s,
> +                          "lsi-mmio", mmio_size);
>      address_space_init(&s->pci_io_as, pci_address_space_io(dev), 
> "lsi-pci-io");
>      qdev_init_gpio_out(d, &s->ext_irq, 1);
>  
> 


ATB,

Mark.