acpi_pci: Add quirk for PSTAT_PME-before-detach

In order to signal to Graviton [123] systems that a device is ready
to be "ejected" (after a detach request is made via the EC2 API) we
need to set PCIM_PSTAT_PME to 1 and PCIM_PSTAT_PMEENABLE to 0.  We are
not aware of any rationale for this requirement beyond "another OS
kernel happens to do this", i.e. this is effectively bug-for-bug
compatibility.

Arguably this should be done by the ACPI _EJ0 method on these systems,
but it is not.

Create a new ACPI_Q_CLEAR_PME_ON_DETACH quirk and set it in EC2 AMIs,
and add the PCI register write to acpi_pci_device_notify_handler when
that quirk is set.

Reviewed by:	jhb
MFC after:	1 month
Sponsored by:	Amazon
Differential Revision:	https://reviews.freebsd.org/D49146

3 files changed, 17 insertions, 2 deletions

diff --git a/release/tools/ec2.conf b/release/tools/ec2.conf
index b5a91d47decf..a8fc3854a0e2 100644
--- a/release/tools/ec2.conf
+++ b/release/tools/ec2.conf
@@ -72,8 +72,11 @@ ec2_common() {
 
 	# Graviton 1 through Graviton 4 have a bug in their ACPI where they
 	# mark the PL061's pins as needing to be configured in PullUp mode
-	# (in fact the PL061 has no pullup/pulldown resistors).
-	echo 'debug.acpi.quirks="8"' >> ${DESTDIR}/boot/loader.conf
+	# (in fact the PL061 has no pullup/pulldown resistors).  Graviton 1
+	# through Graviton 3 have non-functional PCI _EJ0 and need a value
+	# written to the PCI power status register in order to eject a
+	# device.
+	echo 'debug.acpi.quirks="24"' >> ${DESTDIR}/boot/loader.conf
 
 	# Load the kernel module for the Amazon "Elastic Network Adapter"
 	echo 'if_ena_load="YES"' >> ${DESTDIR}/boot/loader.conf
diff --git a/sys/dev/acpica/acpi_pci.c b/sys/dev/acpica/acpi_pci.c
index 6411af02ee58..97704111839b 100644
--- a/sys/dev/acpica/acpi_pci.c
+++ b/sys/dev/acpica/acpi_pci.c
@@ -391,6 +391,8 @@ acpi_pci_device_notify_handler(ACPI_HANDLE h, UINT32 notify, void *context)
 {
 	device_t child, dev;
 	ACPI_STATUS status;
+	int pmc;
+	uint16_t pmstat;
 	int error;
 
 	dev = context;
@@ -416,6 +418,13 @@ acpi_pci_device_notify_handler(ACPI_HANDLE h, UINT32 notify, void *context)
 			    device_get_nameunit(child), error);
 			return;
 		}
+		if ((acpi_quirks & ACPI_Q_CLEAR_PME_ON_DETACH) &&
+		    (pci_find_cap(child, PCIY_PMG, &pmc) == 0)) {
+			pmstat = pci_read_config(child, pmc + PCIR_POWER_STATUS, 2);
+			pmstat &= ~PCIM_PSTAT_PMEENABLE;
+			pmstat |= PCIM_PSTAT_PME;
+			pci_write_config(child, pmc + PCIR_POWER_STATUS, pmstat, 2);
+		}
 		status = acpi_SetInteger(h, "_EJ0", 1);
 		if (ACPI_FAILURE(status)) {
 			bus_topo_unlock();
diff --git a/sys/dev/acpica/acpivar.h b/sys/dev/acpica/acpivar.h
index 668d0b51a1f3..830764434f48 100644
--- a/sys/dev/acpica/acpivar.h
+++ b/sys/dev/acpica/acpivar.h
@@ -230,6 +230,8 @@ extern struct mtx			acpi_mutex;
  *	compatible flag and ignoring overrides that redirect IRQ 0 to pin 2.
  * ACPI_Q_AEI_NOPULL: Specifies that _AEI objects incorrectly designate pins
  *	as "PullUp" and they should be treated as "NoPull" instead.
+ * ACPI_Q_CLEAR_PME_ON_DETACH: Specifies that PCIM_PSTAT_(PME & ~PMEENABLE)
+ *	should be written to the power status register as part of ACPI Eject.
  */
 extern int	acpi_quirks;
 #define ACPI_Q_OK		0
@@ -237,6 +239,7 @@ extern int	acpi_quirks;
 #define ACPI_Q_TIMER		(1 << 1)
 #define ACPI_Q_MADT_IRQ0	(1 << 2)
 #define ACPI_Q_AEI_NOPULL	(1 << 3)
+#define ACPI_Q_CLEAR_PME_ON_DETACH	(1 << 4)
 
 #if defined(__amd64__) || defined(__i386__)
 /*