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From:   Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
To:     linux-pm@vger.kernel.org, loongarch@lists.linux.dev,
        linux-acpi@vger.kernel.org, linux-arch@vger.kernel.org,
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        x86@kernel.org, acpica-devel@lists.linuxfoundation.org,
        linux-csky@vger.kernel.org, linux-doc@vger.kernel.org,
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Cc:     Salil Mehta <salil.mehta@huawei.com>,
        Jean-Philippe Brucker <jean-philippe@linaro.org>,
        jianyong.wu@arm.com, justin.he@arm.com,
        James Morse <james.morse@arm.com>
Subject: [PATCH RFC v3 01/21] ACPI: Only enumerate enabled (or functional)
 devices
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Message-Id: <E1rDOfs-00DvjY-HQ@rmk-PC.armlinux.org.uk>
Sender: Russell King <rmk@armlinux.org.uk>
Date:   Wed, 13 Dec 2023 12:49:16 +0000
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From: James Morse <james.morse@arm.com>

Today the ACPI enumeration code 'visits' all devices that are present.

This is a problem for arm64, where CPUs are always present, but not
always enabled. When a device-check occurs because the firmware-policy
has changed and a CPU is now enabled, the following error occurs:
| acpi ACPI0007:48: Enumeration failure

This is ultimately because acpi_dev_ready_for_enumeration() returns
true for a device that is not enabled. The ACPI Processor driver
will not register such CPUs as they are not 'decoding their resources'.

Change acpi_dev_ready_for_enumeration() to also check the enabled bit.
ACPI allows a device to be functional instead of maintaining the
present and enabled bit. Make this behaviour an explicit check with
a reference to the spec, and then check the present and enabled bits.
This is needed to avoid enumerating present && functional devices that
are not enabled.

Signed-off-by: James Morse <james.morse@arm.com>
Tested-by: Miguel Luis <miguel.luis@oracle.com>
Tested-by: Vishnu Pajjuri <vishnu@os.amperecomputing.com>
Tested-by: Jianyong Wu <jianyong.wu@arm.com>
Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
---
If this change causes problems on deployed hardware, I suggest an
arch opt-in: ACPI_IGNORE_STA_ENABLED, that causes
acpi_dev_ready_for_enumeration() to only check the present bit.

Changes since RFC v2:
 * Incorporate comment suggestion by Gavin Shan.
Other review comments from Jonathan Cameron not yet addressed.
---
 drivers/acpi/device_pm.c    |  2 +-
 drivers/acpi/device_sysfs.c |  2 +-
 drivers/acpi/internal.h     |  1 -
 drivers/acpi/property.c     |  2 +-
 drivers/acpi/scan.c         | 24 ++++++++++++++----------
 5 files changed, 17 insertions(+), 14 deletions(-)

diff --git a/drivers/acpi/device_pm.c b/drivers/acpi/device_pm.c
index 3b4d048c4941..e3c80f3b3b57 100644
--- a/drivers/acpi/device_pm.c
+++ b/drivers/acpi/device_pm.c
@@ -313,7 +313,7 @@ int acpi_bus_init_power(struct acpi_device *device)
 		return -EINVAL;
 
 	device->power.state = ACPI_STATE_UNKNOWN;
-	if (!acpi_device_is_present(device)) {
+	if (!acpi_dev_ready_for_enumeration(device)) {
 		device->flags.initialized = false;
 		return -ENXIO;
 	}
diff --git a/drivers/acpi/device_sysfs.c b/drivers/acpi/device_sysfs.c
index 23373faa35ec..a0256d2493a7 100644
--- a/drivers/acpi/device_sysfs.c
+++ b/drivers/acpi/device_sysfs.c
@@ -141,7 +141,7 @@ static int create_pnp_modalias(const struct acpi_device *acpi_dev, char *modalia
 	struct acpi_hardware_id *id;
 
 	/* Avoid unnecessarily loading modules for non present devices. */
-	if (!acpi_device_is_present(acpi_dev))
+	if (!acpi_dev_ready_for_enumeration(acpi_dev))
 		return 0;
 
 	/*
diff --git a/drivers/acpi/internal.h b/drivers/acpi/internal.h
index 866c7c4ed233..a1b45e345bcc 100644
--- a/drivers/acpi/internal.h
+++ b/drivers/acpi/internal.h
@@ -107,7 +107,6 @@ int acpi_device_setup_files(struct acpi_device *dev);
 void acpi_device_remove_files(struct acpi_device *dev);
 void acpi_device_add_finalize(struct acpi_device *device);
 void acpi_free_pnp_ids(struct acpi_device_pnp *pnp);
-bool acpi_device_is_present(const struct acpi_device *adev);
 bool acpi_device_is_battery(struct acpi_device *adev);
 bool acpi_device_is_first_physical_node(struct acpi_device *adev,
 					const struct device *dev);
diff --git a/drivers/acpi/property.c b/drivers/acpi/property.c
index 6979a3f9f90a..14d6948fd88a 100644
--- a/drivers/acpi/property.c
+++ b/drivers/acpi/property.c
@@ -1420,7 +1420,7 @@ static bool acpi_fwnode_device_is_available(const struct fwnode_handle *fwnode)
 	if (!is_acpi_device_node(fwnode))
 		return false;
 
-	return acpi_device_is_present(to_acpi_device_node(fwnode));
+	return acpi_dev_ready_for_enumeration(to_acpi_device_node(fwnode));
 }
 
 static const void *
diff --git a/drivers/acpi/scan.c b/drivers/acpi/scan.c
index 02bb2cce423f..728649a2a251 100644
--- a/drivers/acpi/scan.c
+++ b/drivers/acpi/scan.c
@@ -304,7 +304,7 @@ static int acpi_scan_device_check(struct acpi_device *adev)
 	int error;
 
 	acpi_bus_get_status(adev);
-	if (acpi_device_is_present(adev)) {
+	if (acpi_dev_ready_for_enumeration(adev)) {
 		/*
 		 * This function is only called for device objects for which
 		 * matching scan handlers exist.  The only situation in which
@@ -338,7 +338,7 @@ static int acpi_scan_bus_check(struct acpi_device *adev, void *not_used)
 	int error;
 
 	acpi_bus_get_status(adev);
-	if (!acpi_device_is_present(adev)) {
+	if (!acpi_dev_ready_for_enumeration(adev)) {
 		acpi_scan_device_not_enumerated(adev);
 		return 0;
 	}
@@ -1913,11 +1913,6 @@ static bool acpi_device_should_be_hidden(acpi_handle handle)
 	return true;
 }
 
-bool acpi_device_is_present(const struct acpi_device *adev)
-{
-	return adev->status.present || adev->status.functional;
-}
-
 static bool acpi_scan_handler_matching(struct acpi_scan_handler *handler,
 				       const char *idstr,
 				       const struct acpi_device_id **matchid)
@@ -2381,16 +2376,25 @@ EXPORT_SYMBOL_GPL(acpi_dev_clear_dependencies);
  * acpi_dev_ready_for_enumeration - Check if the ACPI device is ready for enumeration
  * @device: Pointer to the &struct acpi_device to check
  *
- * Check if the device is present and has no unmet dependencies.
+ * Check if the device is functional or enabled and has no unmet dependencies.
  *
- * Return true if the device is ready for enumeratino. Otherwise, return false.
+ * Return true if the device is ready for enumeration. Otherwise, return false.
  */
 bool acpi_dev_ready_for_enumeration(const struct acpi_device *device)
 {
 	if (device->flags.honor_deps && device->dep_unmet)
 		return false;
 
-	return acpi_device_is_present(device);
+	/*
+	 * ACPI 6.5's 6.3.7 "_STA (Device Status)" allows firmware to return
+	 * (!present && functional) for certain types of devices that should be
+	 * enumerated. Note that the enabled bit can't be sert until the present
+	 * bit is set.
+	 */
+	if (device->status.present)
+		return device->status.enabled;
+	else
+		return device->status.functional;
 }
 EXPORT_SYMBOL_GPL(acpi_dev_ready_for_enumeration);
 
-- 
2.30.2