Comment 2 for bug 1906905

Per the "NCR89C105 Chip Specification" referenced in the header:

                  Chip-level Address Map

  ------------------------------------------------------------------
  | 1D0 0000 -> | Counter/Timers | W,D |
  | 1DF FFFF | | |
  ...

  The address map indicated the allowed accesses at each address.
  [...] W indicates a word access, and D indicates a double-word
  access.

The SLAVIO timer controller is implemented expecting 32-bit accesses.
Commit a3d12d073e1 restricted the memory accesses to 32-bit, while
the device allows 64-bit accesses.

This was not an issue until commit 5d971f9e67 which reverted
("memory: accept mismatching sizes in memory_region_access_valid").

Fix by renaming .valid MemoryRegionOps as .impl, and add the valid
access range (W -> 4, D -> 8).

Since commit 21786c7e598 ("memory: Log invalid memory accesses")
this class of bug can be quickly debugged displaying 'guest_errors'
accesses, as:

  $ qemu-system-sparc -M SS-20 -m 256 -bios ss20_v2.25_rom -serial stdio -d guest_errors

  Power-ON Reset
  Invalid access at addr 0x0, size 8, region 'timer-1', reason: invalid size (min:4 max:4)

  $ qemu-system-sparc -M SS-20 -m 256 -bios ss20_v2.25_rom -monitor stdio -S
  (qemu) info mtree
  address-space: memory
    0000000000000000-ffffffffffffffff (prio 0, i/o): system
      ...
      0000000ff1300000-0000000ff130000f (prio 0, i/o): timer-1
             ^^^^^^^^^ ^^^^^^^
                   \ memory region base address and name /

  (qemu) info qtree
  bus: main-system-bus
    dev: slavio_timer, id "" <-- device type name
      gpio-out "sysbus-irq" 17
      num_cpus = 1 (0x1)
      mmio 0000000ff1310000/0000000000000014
      mmio 0000000ff1300000/0000000000000010 <--- base address
      mmio 0000000ff1301000/0000000000000010
      mmio 0000000ff1302000/0000000000000010
      ...

Reported-by: Yap KV <email address hidden>
Buglink: https://bugs.launchpad.net/bugs/1906905
Fixes: a3d12d073e1 ("slavio_timer: convert to memory API")
Signed-off-by: Philippe Mathieu-Daudé <email address hidden>
---
Cc: Benoit Canet <email address hidden>
Cc: <email address hidden>
Signed-off-by: Philippe Mathieu-Daudé <email address hidden>
---
 hw/timer/slavio_timer.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/hw/timer/slavio_timer.c b/hw/timer/slavio_timer.c
index 5b2d20cb6a5..03e33fc5926 100644
--- a/hw/timer/slavio_timer.c
+++ b/hw/timer/slavio_timer.c
@@ -331,6 +331,10 @@ static const MemoryRegionOps slavio_timer_mem_ops = {
     .write = slavio_timer_mem_writel,
     .endianness = DEVICE_NATIVE_ENDIAN,
     .valid = {
+ .min_access_size = 4,
+ .max_access_size = 8,
+ },
+ .impl = {
         .min_access_size = 4,
         .max_access_size = 4,
     },
--
2.26.2