Re: [PATCH v2] PCI: Call _REG when saving/restoring PCI state
From: Limonciello, Mario
Date: Tue Jun 06 2023 - 15:41:54 EST
On 6/6/2023 2:23 PM, Bjorn Helgaas wrote:
On Tue, Jun 06, 2023 at 11:23:21AM -0500, Mario Limonciello wrote:
ASMedia PCIe GPIO controllers fail functional tests after returning from
suspend (S3 or s2idle). This is because the BIOS checks whether the
OSPM has called the `_REG` method to determine whether it can interact with
the OperationRegion assigned to the device.
As described in 6.5.4 in the APCI spec, `_REG` is used to inform the AML
code on the availability of an operation region.
To fix this issue, call acpi_evaluate_reg() when saving and restoring the
state of PCI devices.
Link: https://uefi.org/htmlspecs/ACPI_Spec_6_4_html/06_Device_Configuration/Device_Configuration.html#reg-region
Signed-off-by: Mario Limonciello <mario.limonciello@xxxxxxx>
---
v1->v2:
* Handle case of no CONFIG_ACPI
* Rename function
* Update commit message
* Move ACPI calling code into pci-acpi.c instead
* Cite the ACPI spec
Thanks for the spec reference (s/APCI/ACPI/ and add the revision if
you rev this (r6.5 is the latest, AFAIK) if you rev this).
I don't see text in that section that connects S3 with _REG. If it's
there, you might have to quote the relevant sentence or two in the
commit log.
I don't think there is anything the spec connecting this
with S3. At least from my perspective S3 is the reason
this was exposed but there is a deficiency that exists
that _REG is not being called by Linux.
I intend to re-word the commit message something to the
effect of explaining what _REG does and why _REG should be
called, along with citations.
Then in another paragraph "Fixing this resolves an issue ...".
You mentioned _REG being sort of a mutex to synchronize OSPM vs
platform access; if there's spec language to that effect, let's cite
it.
That sentence I included was cited from the spec.
Ideally we should have been able to read the PCI and ACPI specs and
implement this without tripping over problem on this particular
hardware. I'm looking for the text that enables that "clean-room"
implementation. If the spec doesn't have that text, it's either a
hole in the spec or a BIOS defect that depends on something the spec
doesn't require.
IMO both the spec and BIOS are correct, it's a Linux
issue that _REG wasn't used.
Hopefully disconnecting the issue as just an example
will achieve what you're looking for.
Doing this in pci_save_state() still seems wrong to me. For example,
e1000_probe() calls pci_save_state(), but this is not part of suspend.
IIUC, this patch will disconnect the opregion when we probe an e1000
NIC. Is that what you intend?
Thanks for pointing this one out. I was narrowly focused
on callers in PCI core. This was a caller I wasn't
aware of; I agree it doesn't make sense.
I think pci_set_power_state() might be another good
candidate to use. What do you think of this?
Or can you suggest another call site? I'm hesitant
to put this into PCI suspend/resume code, because
I think this same issue could happen at runtime too.
---
drivers/pci/pci-acpi.c | 10 ++++++++++
drivers/pci/pci.c | 14 ++++++++++++++
drivers/pci/pci.h | 2 ++
3 files changed, 26 insertions(+)
diff --git a/drivers/pci/pci-acpi.c b/drivers/pci/pci-acpi.c
index 1698205dd73c..abc8bcfc2c71 100644
--- a/drivers/pci/pci-acpi.c
+++ b/drivers/pci/pci-acpi.c
@@ -1209,6 +1209,16 @@ void acpi_pci_remove_bus(struct pci_bus *bus)
acpi_pci_slot_remove(bus);
}
+void acpi_pci_set_register_access(struct pci_dev *dev, bool enable)
+{
+ int val = enable ? ACPI_REG_CONNECT : ACPI_REG_DISCONNECT;
+ int ret = acpi_evaluate_reg(ACPI_HANDLE(&dev->dev),
+ ACPI_ADR_SPACE_PCI_CONFIG, val);
+ if (ret)
+ pci_dbg(dev, "ACPI _REG %s evaluation failed (%d)\n",
+ val ? "connect" : "disconnect", ret);
+}
+
/* ACPI bus type */
diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index e38c2f6eebd4..b2f1f603ec62 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -1068,6 +1068,14 @@ static inline bool platform_pci_bridge_d3(struct pci_dev *dev)
return acpi_pci_bridge_d3(dev);
}
+static inline void platform_set_register_access(struct pci_dev *dev, bool en)
+{
+ if (pci_use_mid_pm())
+ return;
+
+ acpi_pci_set_register_access(dev, en);
+}
+
/**
* pci_update_current_state - Read power state of given device and cache it
* @dev: PCI device to handle.
@@ -1645,6 +1653,9 @@ static void pci_restore_ltr_state(struct pci_dev *dev)
int pci_save_state(struct pci_dev *dev)
{
int i;
+
+ platform_set_register_access(dev, false);
+
/* XXX: 100% dword access ok here? */
for (i = 0; i < 16; i++) {
pci_read_config_dword(dev, i * 4, &dev->saved_config_space[i]);
@@ -1790,6 +1801,8 @@ void pci_restore_state(struct pci_dev *dev)
pci_enable_acs(dev);
pci_restore_iov_state(dev);
+ platform_set_register_access(dev, true);
+
dev->state_saved = false;
}
EXPORT_SYMBOL(pci_restore_state);
@@ -3203,6 +3216,7 @@ void pci_pm_init(struct pci_dev *dev)
pci_read_config_word(dev, PCI_STATUS, &status);
if (status & PCI_STATUS_IMM_READY)
dev->imm_ready = 1;
+ platform_set_register_access(dev, true);
}
static unsigned long pci_ea_flags(struct pci_dev *dev, u8 prop)
diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h
index ffccb03933e2..78961505aae2 100644
--- a/drivers/pci/pci.h
+++ b/drivers/pci/pci.h
@@ -703,6 +703,7 @@ void acpi_pci_refresh_power_state(struct pci_dev *dev);
int acpi_pci_wakeup(struct pci_dev *dev, bool enable);
bool acpi_pci_need_resume(struct pci_dev *dev);
pci_power_t acpi_pci_choose_state(struct pci_dev *pdev);
+void acpi_pci_set_register_access(struct pci_dev *dev, bool enable);
#else
static inline int pci_dev_acpi_reset(struct pci_dev *dev, bool probe)
{
@@ -742,6 +743,7 @@ static inline pci_power_t acpi_pci_choose_state(struct pci_dev *pdev)
{
return PCI_POWER_ERROR;
}
+static inline void acpi_pci_set_register_access(struct pci_dev *dev, bool enable) {}
#endif
#ifdef CONFIG_PCIEASPM
--
2.34.1