Re: [PATCH v2 09/13] hw/ppc/e500: Implement pflash handling

[Philippe Mathieu-Daudé]

On 3/10/22 22:31, Bernhard Beschow wrote:
> Allows e500 boards to have their root file system reside on flash using
> only builtin devices located in the eLBC memory region.
>
> Note that the flash memory area is only created when a -pflash argument is
> given, and that the size is determined by the given file. The idea is to
> put users into control.
>
> Signed-off-by: Bernhard Beschow <shentey@gmail.com>
> ---
>   docs/system/ppc/ppce500.rst | 12 ++++++
>   hw/ppc/Kconfig              |  1 +
>   hw/ppc/e500.c               | 76 +++++++++++++++++++++++++++++++++++++
>   3 files changed, 89 insertions(+)

> @@ -856,6 +892,7 @@ void ppce500_init(MachineState *machine)
>       unsigned int pci_irq_nrs[PCI_NUM_PINS] = {1, 2, 3, 4};
>       IrqLines *irqs;
>       DeviceState *dev, *mpicdev;
> +    DriveInfo *dinfo;
>       CPUPPCState *firstenv = NULL;
>       MemoryRegion *ccsr_addr_space;
>       SysBusDevice *s;
> @@ -1024,6 +1061,45 @@ void ppce500_init(MachineState *machine)
>                                   pmc->platform_bus_base,
>                                   &pms->pbus_dev->mmio);
>   
> +    dinfo = drive_get(IF_PFLASH, 0, 0);
> +    if (dinfo) {
> +        BlockBackend *blk = blk_by_legacy_dinfo(dinfo);
> +        BlockDriverState *bs = blk_bs(blk);
> +        uint64_t size = bdrv_getlength(bs);
> +        uint64_t mmio_size = pms->pbus_dev->mmio.size;
> +        uint32_t sector_len = 64 * KiB;
> +
> +        if (ctpop64(size) != 1) {
> +            error_report("Size of pflash file must be a power of two.");

This is a PFLASH restriction (which you already fixed in the previous
patch), not a board one.

> +            exit(1);
> +        }
> +
> +        if (size > mmio_size) {
> +            error_report("Size of pflash file must not be bigger than %" PRIu64
> +                         " bytes.", mmio_size);

There is no hardware limitation here, you can wire flash bigger than the
memory aperture. What is above the aperture will simply be ignored.

Should we display a warning here instead of a fatal error?

> +            exit(1);
> +        }
> +
> +        assert(QEMU_IS_ALIGNED(size, sector_len));

Similarly, this doesn't seem a problem the board code should worry
about: better to defer it to PFLASH realize().

> +        dev = qdev_new(TYPE_PFLASH_CFI01);
> +        qdev_prop_set_drive(dev, "drive", blk);
> +        qdev_prop_set_uint32(dev, "num-blocks", size / sector_len);
> +        qdev_prop_set_uint64(dev, "sector-length", sector_len);
> +        qdev_prop_set_uint8(dev, "width", 2);
> +        qdev_prop_set_bit(dev, "big-endian", true);
> +        qdev_prop_set_uint16(dev, "id0", 0x89);
> +        qdev_prop_set_uint16(dev, "id1", 0x18);
> +        qdev_prop_set_uint16(dev, "id2", 0x0000);
> +        qdev_prop_set_uint16(dev, "id3", 0x0);
> +        qdev_prop_set_string(dev, "name", "e500.flash");
> +        s = SYS_BUS_DEVICE(dev);
> +        sysbus_realize_and_unref(s, &error_fatal);
> +
> +        memory_region_add_subregion(&pms->pbus_dev->mmio, 0,
> +                                    sysbus_mmio_get_region(s, 0));
> +    }
> +
>       /*
>        * Smart firmware defaults ahead!
>        *