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Re: [PATCH v2 04/13] vt82c686: Fix up power management io base and confi

From: BALATON Zoltan
Subject: Re: [PATCH v2 04/13] vt82c686: Fix up power management io base and config
Date: Sat, 20 Feb 2021 23:33:00 +0100 (CET)

On Sat, 20 Feb 2021, Philippe Mathieu-Daudé wrote:
On 1/9/21 9:16 PM, BALATON Zoltan wrote:
Similar to the SMBus io registers there is a power management io range
that is set via similar base address reg and enable bit. Some handling
of this was already there but with several problems: using the wrong
registers and bits, wrong size range, not acually updating mapping and
handling reset correctly, nor emulating any of the actual io
registers. Some of these errors are fixed up here.

After this patch we use the correct base address register, enable bit
and region size and allow guests to map/unmap this region and
correctly reset all registers to default values on reset but we still
don't emulate any of the registers in this range.

^^ One change,

vv Another change.

This again is just two hunks and a bit from this patch that is fairly trivial so I did not think that would need a separate patch but in this case maybe simplifies the main patch so you don't have to mentally ignore the pm_io_ops parts while reviewing it.

Previously just an empty RAM region was mapped on realize, now we add
an empty io range logging access instead. I think the pm timer should
be hooked up here but not sure guests need it. PMON on fuloong2e sets
a base address but does not seem to enable region; the pegasos2
firmware pokes some regs but continues anyway so don't know if
anything would make use of these facilities. Therefore this is just a
clean up of previous state for now and not intending to fully
implement missing functionality which could be done later if some
guests need it.

I split your patch in 2.

Thanks again.

Signed-off-by: BALATON Zoltan <balaton@eik.bme.hu>
 hw/isa/trace-events |  2 ++
 hw/isa/vt82c686.c   | 56 ++++++++++++++++++++++++++++++++-------------
 2 files changed, 42 insertions(+), 16 deletions(-)

diff --git a/hw/isa/trace-events b/hw/isa/trace-events
index d267d3e652..641d69eedf 100644
--- a/hw/isa/trace-events
+++ b/hw/isa/trace-events
@@ -17,5 +17,7 @@ apm_io_write(uint8_t addr, uint8_t val) "write addr=0x%x 
 # vt82c686.c
 via_isa_write(uint32_t addr, uint32_t val, int len) "addr 0x%x val 0x%x len 
 via_pm_write(uint32_t addr, uint32_t val, int len) "addr 0x%x val 0x%x len 
+via_pm_io_read(uint32_t addr, uint32_t val, int len) "addr 0x%x val 0x%x len 
+via_pm_io_write(uint32_t addr, uint32_t val, int len) "addr 0x%x val 0x%x len 
 via_superio_read(uint8_t addr, uint8_t val) "addr 0x%x val 0x%x"
 via_superio_write(uint8_t addr, uint32_t val) "addr 0x%x val 0x%x"
diff --git a/hw/isa/vt82c686.c b/hw/isa/vt82c686.c
index 9c4d153022..fc2a1f4430 100644
--- a/hw/isa/vt82c686.c
+++ b/hw/isa/vt82c686.c
@@ -39,14 +39,11 @@ struct VT686PMState {

 static void pm_io_space_update(VT686PMState *s)
-    uint32_t pm_io_base;
-    pm_io_base = pci_get_long(s->dev.config + 0x40);
-    pm_io_base &= 0xffc0;
+    uint32_t pmbase = pci_get_long(s->dev.config + 0x48) & 0xff80UL;

0x48 is Power Management I/O Base,
0xff80UL is mask for Power Management I/O Register Base Address,

-    memory_region_set_enabled(&s->io, s->dev.config[0x80] & 1);
-    memory_region_set_address(&s->io, pm_io_base);
+    memory_region_set_address(&s->io, pmbase);
+    memory_region_set_enabled(&s->io, s->dev.config[0x41] & BIT(7));

0x41 is General Configuration 1,
bit 7 is I/O Enable for ACPI I/O Base,


@@ -92,6 +89,13 @@ static void pm_write_config(PCIDevice *d, uint32_t addr, 
uint32_t val, int len)

     trace_via_pm_write(addr, val, len);
     pci_default_write_config(d, addr, val, len);
+    if (ranges_overlap(addr, len, 0x48, 4)) {
+        uint32_t v = pci_get_long(s->dev.config + 0x48);
+        pci_set_long(s->dev.config + 0x48, (v & 0xff80UL) | 1);

bit 0 is always set, OK.

+    }
+    if (range_covers_byte(addr, len, 0x41)) {

Access to General Configuration. Why not use both registers?

      if (ranges_overlap(addr, len, 0x40, 2)) {

Hmm, not sure, I've forgotten by now. I think we only have to do anything if the memory region is enabled or disabled which is the bit in 0x41 so if other parts of the reg are written we don't have to call pm_io_space_update(). We just store the value in the reg in that case but only need to update the region when the enable bit is changed.

+        pm_io_space_update(s);
+    }
     if (ranges_overlap(addr, len, 0x90, 4)) {
         uint32_t v = pci_get_long(s->dev.config + 0x90);
         pci_set_long(s->dev.config + 0x90, (v & 0xfff0UL) | 1);
@@ -102,6 +106,27 @@ static void pm_write_config(PCIDevice *d, uint32_t addr, 
uint32_t val, int len)

+static void pm_io_write(void *op, hwaddr addr, uint64_t data, unsigned size)
+    trace_via_pm_io_write(addr, data, size);
+static uint64_t pm_io_read(void *op, hwaddr addr, unsigned size)
+    trace_via_pm_io_read(addr, 0, size);
+    return 0;
+static const MemoryRegionOps pm_io_ops = {
+    .read = pm_io_read,
+    .write = pm_io_write,
+    .endianness = DEVICE_NATIVE_ENDIAN,
+    .impl = {
+        .min_access_size = 1,
+        .max_access_size = 1,
+    },
 static void pm_update_sci(VT686PMState *s)
     int sci_level, pmsts;
@@ -128,35 +153,34 @@ static void vt82c686b_pm_reset(DeviceState *d)
     VT686PMState *s = VT82C686B_PM(d);

+    memset(s->dev.config + PCI_CONFIG_HEADER_SIZE, 0,
+    /* Power Management IO base */
+    pci_set_long(s->dev.config + 0x48, 1);

bit 1 always set, OK.

     /* SMBus IO base */
     pci_set_long(s->dev.config + 0x90, 1);
-    s->dev.config[0xd2] = 0;

+    pm_io_space_update(s);

 static void vt82c686b_pm_realize(PCIDevice *dev, Error **errp)
     VT686PMState *s = VT82C686B_PM(dev);
-    uint8_t *pci_conf;

-    pci_conf = s->dev.config;
-    pci_set_word(pci_conf + PCI_COMMAND, 0);
-    pci_set_word(pci_conf + PCI_STATUS, PCI_STATUS_FAST_BACK |
+    pci_set_word(dev->config + PCI_STATUS, PCI_STATUS_FAST_BACK |

-    /* 0x48-0x4B is Power Management I/O Base */
-    pci_set_long(pci_conf + 0x48, 0x00000001);
     pm_smbus_init(DEVICE(s), &s->smb, false);
     memory_region_add_subregion(pci_address_space_io(dev), 0, &s->smb.io);
     memory_region_set_enabled(&s->smb.io, false);

     apm_init(dev, &s->apm, NULL, s);

-    memory_region_init(&s->io, OBJECT(dev), "vt82c686-pm", 64);
+    memory_region_init_io(&s->io, OBJECT(dev), &pm_io_ops, s,
+                          "vt82c686-pm", 0x100);

Section "Configuration Space Power Management Registers" describes:

 4B-48: Power Mgmt I/O Base (256 Bytes)

Section "Offset 4B-48 – Power Management I/O Base" describes:

 Port Address for the base of the 128-byte Power
 Management I/O Register block, corresponding to

At least we are sure 64 bytes isn't enough indeed, but is it 128 or 256?

The regs in this range for 82c686b go up to 0x4C so it's definitely over 64 but seems to be less than 128. The vt8231 docs also say 128 byte here so maybe this was a typo and 128 bytes length would be enough.

+    memory_region_add_subregion(pci_address_space_io(dev), 0, &s->io);
     memory_region_set_enabled(&s->io, false);
-    memory_region_add_subregion(get_system_io(), 0, &s->io);

     acpi_pm_tmr_init(&s->ar, pm_tmr_timer, &s->io);
     acpi_pm1_evt_init(&s->ar, pm_tmr_timer, &s->io);

TBH it took me almost 1h to review this single patch.

Yes, sorry but these kinds of patches need reading the chip docs which takes some time. It took me a few days to write this simgle patch though because I had to learn how the chip works and understand the code already there and testing with guests so reviewing it is still less than that. ;-)

Thanks for your efforts, I hope to get this series in so I can submit the remaining ones adding pegasos2 emulation so it can get in for the next release. Let me know if I can help your review by whatever changes you would need in other patches.


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