[PATCH 3/5] hw/pci-host/bonito: Allow PCI config accesses smaller than 32-bit

["Philippe Mathieu-Daudé" <f4bug@amsat.org>]

When running the official PMON firmware for the Fuloong 2E, we see
8-bit and 16-bit accesses to PCI config space:

  $ qemu-system-mips64el -M fuloong2e -bios pmon_2e.bin \
    -trace -trace bonito\* -trace pci_cfg\*

  pci_cfg_write vt82c686b-pm 05:4 @0x90 <- 0xeee1
  bonito_spciconf_small_access PCI config address is smaller then 32-bit, addr: 0x4d2, size: 2
  pci_cfg_write vt82c686b-pm 05:4 @0xd2 <- 0x1
  pci_cfg_write vt82c686b-pm 05:4 @0x4 <- 0x1
  pci_cfg_write vt82c686b-isa 05:0 @0x4 <- 0x7
  bonito_spciconf_small_access PCI config address is smaller then 32-bit, addr: 0x81, size: 1
  pci_cfg_read vt82c686b-isa 05:0 @0x81 -> 0x0
  bonito_spciconf_small_access PCI config address is smaller then 32-bit, addr: 0x81, size: 1
  pci_cfg_write vt82c686b-isa 05:0 @0x81 <- 0x80
  bonito_spciconf_small_access PCI config address is smaller then 32-bit, addr: 0x83, size: 1
  pci_cfg_write vt82c686b-isa 05:0 @0x83 <- 0x89
  bonito_spciconf_small_access PCI config address is smaller then 32-bit, addr: 0x85, size: 1
  pci_cfg_write vt82c686b-isa 05:0 @0x85 <- 0x3
  bonito_spciconf_small_access PCI config address is smaller then 32-bit, addr: 0x5a, size: 1
  pci_cfg_write vt82c686b-isa 05:0 @0x5a <- 0x7
  bonito_spciconf_small_access PCI config address is smaller then 32-bit, addr: 0x85, size: 1
  pci_cfg_write vt82c686b-isa 05:0 @0x85 <- 0x1

Also this is what the Linux kernel does since it supports the Bonito
north bridge:
https://elixir.bootlin.com/linux/v2.6.15/source/arch/mips/pci/ops-bonito64.c#L85

So it seems safe to assume the datasheet is incomplete or outdated
regarding the address constraints.

This problem was exposed by commit 911629e6d3773a8adeab48b
("vt82c686: Fix SMBus IO base and configuration registers").

Reported-by: BALATON Zoltan <balaton@eik.bme.hu>
Suggested-by: Jiaxun Yang <jiaxun.yang@flygoat.com>
Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
---
 hw/pci-host/bonito.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/hw/pci-host/bonito.c b/hw/pci-host/bonito.c
index 751fdcec689..3c10608c9a2 100644
--- a/hw/pci-host/bonito.c
+++ b/hw/pci-host/bonito.c
@@ -187,7 +187,7 @@ FIELD(BONGENCFG, PCIQUEUE,      12, 1)
 #define BONITO_PCICONF_FUN_MASK        0x700    /* [10:8] */
 #define BONITO_PCICONF_FUN_OFFSET      8
 #define BONITO_PCICONF_REG_MASK_DS     (~3)         /* Per datasheet */
-#define BONITO_PCICONF_REG_MASK        0xFC
+#define BONITO_PCICONF_REG_MASK_HW     0xff         /* As seen on hardware */
 #define BONITO_PCICONF_REG_OFFSET      0
 
 
@@ -466,7 +466,7 @@ static uint32_t bonito_sbridge_pciaddr(void *opaque, hwaddr addr)
              BONITO_PCICONF_IDSEL_OFFSET;
     devno = ctz32(idsel);
     funno = (cfgaddr & BONITO_PCICONF_FUN_MASK) >> BONITO_PCICONF_FUN_OFFSET;
-    regno = (cfgaddr & BONITO_PCICONF_REG_MASK) >> BONITO_PCICONF_REG_OFFSET;
+    regno = (cfgaddr & BONITO_PCICONF_REG_MASK_HW) >> BONITO_PCICONF_REG_OFFSET;
 
     if (idsel == 0) {
         error_report("error in bonito pci config address 0x" TARGET_FMT_plx
-- 
2.31.1