Re: [PATCH v5 RESEND 3/6] firmware: smccc: lfa: Register ACPI notification
From: Vedashree Vidwans
Date: Wed Nov 04 2026 - 22:33:28 EST
Hi Andre
On 11/4/26 12:03, Nirmoy Das wrote:
Hi AndreThe kobject references protect the snapshot objects from being freed, but do not guarantee that the components remain in the firmware inventory.
On 02.11.26 17:54, Andre Przywara wrote:
From: Vedashree Vidwans <vvidwans@xxxxxxxxxx>
The Arm LFA spec describes an ACPI notification mechanism, where the
platform (firmware) can notify an LFA client about newly available
firmware imag updates ("pending images" in LFA terms).
Add a faux device after discovering the existence of an LFA agent via
the SMCCC discovery mechnism, and use that device to check for the ACPI
notification description. Register this when one is provided.
The notification just conveys the fact that at least one firmware image
has now a pending update, it doesn't say which, also there could be more
than one pending. Loop through all images to find every which needs to
be activated, and trigger the activation. We need to do this is a loop,
since an activation might change the number and the status of available
images.
Signed-off-by: Vedashree Vidwans <vvidwans@xxxxxxxxxx>
[Andre: convert from platform driver to smccc bus]
Signed-off-by: Andre Przywara <andre.przywar@xxxxxxx>
---
drivers/firmware/smccc/lfa_fw.c | 154 +++++++++++++++++++++++++++++++-
1 file changed, 153 insertions(+), 1 deletion(-)
diff --git a/drivers/firmware/smccc/lfa_fw.c b/drivers/firmware/smccc/lfa_fw.c
index db2a7fe344d5d..4b4daf79611bb 100644
--- a/drivers/firmware/smccc/lfa_fw.c
+++ b/drivers/firmware/smccc/lfa_fw.c
@@ -33,12 +33,14 @@
* skipped by setting the force_cpu_rendezvous sysfs file to false.
*/
+#include <linux/acpi.h>
#include <linux/arm-smccc.h>
#include <linux/arm-smccc-bus.h>
#include <linux/array_size.h>
#include <linux/delay.h>
#include <linux/fs.h>
#include <linux/init.h>
+#include <linux/kernel.h>
#include <linux/kobject.h>
#include <linux/ktime.h>
#include <linux/list.h>
@@ -49,11 +51,13 @@
#include <linux/stop_machine.h>
#include <linux/string.h>
#include <linux/sysfs.h>
+#include <linux/types.h>
#include <linux/uuid.h>
#include <linux/workqueue.h>
#include <uapi/linux/psci.h>
+#define DRIVER_NAME "ARM_LFA"
#undef pr_fmt
#define pr_fmt(fmt) "Arm LFA: " fmt
@@ -753,6 +757,135 @@ static void clean_fw_components_tree(void)
}
}
+/*
+ * Iterate over all FW components and trigger activation of all activatible and
+ * pending components.
+ * Since we would need to re-enumerate the list of all components after a
+ * successful activation, and this could trigger infinite loops if a firmware
+ * component still appears as pending, we create an array of update candidates
+ * first, then activate each one of them.
+ */
+static void activate_pending_components(void)
+{
+ struct fw_component **all_comps;
+ struct fw_component *comp;
+ struct kobject *kobj;
+ int nr_comps = 0;
+ int ret, i;
+
+ down_read(&smc_lock);
+ spin_lock(&lfa_kset->list_lock);
+ all_comps = kmalloc_array(list_count_nodes(&lfa_kset->list),
+ sizeof(*all_comps), GFP_NOWAIT);
+ if (!all_comps) {
+ spin_unlock(&lfa_kset->list_lock);
+ up_read(&smc_lock);
+ pr_warn("LFA: automatic activation failed: -ENOMEM\n");
+ return;
+ }
+
+ list_for_each_entry(kobj, &lfa_kset->list, entry) {
+ comp = kobj_to_fw_component(kobj);
+
+ if (comp->fw_seq_id == -1)
+ continue; /* Invalid FW component */
+
+ _update_fw_component_pending(comp);
+ if (comp->activation_capable && comp->activation_pending) {
+ kobject_get(&comp->kobj);
+ all_comps[nr_comps++] = comp;
+ }
+ }
+ spin_unlock(&lfa_kset->list_lock);
+ up_read(&smc_lock);
+
+ for (i = 0; i < nr_comps; i++) {
+ comp = all_comps[i];
+
+ ret = prime_fw_component(comp);
For example, the snapshot can contain A and B, and activating A can remove B from the refreshed inventory. The reference keeps B allocated, but its sequence ID becomes `-1`. The subsequent PRIME call does not reject that invalid ID before issuing the SMC.
Could candidates be revalidated under `smc_lock` before issuing component operations? The check needs to cover activation retries too, since inventory can change between calls.
+ if (ret) {
+ pr_warn("LFA: LFA_PRIME failed for component %s\n",
+ kobject_name(&comp->kobj));
+ kobject_put(&comp->kobj);
+ continue;
+ }
+
+ ret = activate_fw_component(comp);
+ if (ret) {
+ pr_warn("LFA: LFA_ACTIVATE failed for component %s\n",
+ kobject_name(&comp->kobj));
+ kobject_put(&comp->kobj);
+ continue;
+ }
+
+ pr_info("%s: automatic activation succeeded\n",
+ kobject_name(&comp->kobj));
+ kobject_put(&comp->kobj);
+ }
+
+ kfree(all_comps);
+}
+
+#ifdef CONFIG_ACPI
+static void lfa_acpi_notify_handler(acpi_handle handle, u32 event, void *data)
+{
+ /* The spec explicitly mentions 0x80 only for the update event. */
+ if (event != 0x80)
+ return;
+
+ activate_pending_components();
+}
+
+static int lfa_register_acpi(struct device *dev)
+{
+ struct acpi_device *acpi_dev;
+ acpi_handle handle;
+ acpi_status status;
+
+ acpi_dev = acpi_dev_get_first_match_dev("ARML0003", NULL, -1);
+ if (!acpi_dev)
+ return -ENODEV;
+ handle = acpi_device_handle(acpi_dev);
+ if (!handle) {
+ acpi_dev_put(acpi_dev);
+ return -ENODEV;
+ }
+
+ /* Register notify handler that indicates LFA updates are available */
+ status = acpi_install_notify_handler(handle, ACPI_DEVICE_NOTIFY,
+ lfa_acpi_notify_handler, NULL);
+ if (ACPI_FAILURE(status)) {
+ acpi_dev_put(acpi_dev);
+ return -EIO;
+ }
+
+ ACPI_COMPANION_SET(dev, acpi_dev);
+
+ return 0;
+}
+
+static void lfa_remove_acpi(struct device *dev)
+{
+ struct acpi_device *acpi_dev = ACPI_COMPANION(dev);
+ acpi_handle handle = acpi_device_handle(acpi_dev);
+
+ if (handle)
+ acpi_remove_notify_handler(handle,
+ ACPI_DEVICE_NOTIFY,
+ lfa_acpi_notify_handler);
+ acpi_dev_put(acpi_dev);
+}
+#else /* !CONFIG_ACPI */
+static int lfa_register_acpi(struct device *dev)
+{
+ return -ENODEV;
+}
+
+static void lfa_remove_acpi(struct device *dev)
+{
+}
+#endif
+
static bool lfa_smccc_has_all_functions(void)
{
struct arm_smccc_1_2_regs regs = { 0 }, res;
@@ -813,13 +946,32 @@ static int lfa_smccc_probe(struct arm_smccc_device *sdev)
if (err != 0) {
kset_unregister(lfa_kset);
destroy_workqueue(fw_comps_update_wq);
+ return err;
+ }
+
+ if (!acpi_disabled) {
+ err = lfa_register_acpi(&sdev->dev);
+ if (!err)
+ pr_info("registered LFA ACPI notification\n");
+ }
+
+ /*
+ * An ACPI notification or an interrupt are optional, but we must
+ * handle errors that occurred during their setup.
+ */
+ if (err != -ENODEV) {
On successful registration, err is zero, so this condition still unregisters the inventory and destroys the workqueue before returning success. Should it be:
if (err && err != -ENODEV) {
Regards,
Nirmoy
+ kset_unregister(lfa_kset);
+ destroy_workqueue(fw_comps_update_wq);
+ return err;
}
- return err;
+ return 0;
}
static void lfa_smccc_remove(struct arm_smccc_device *sdev)
{
+ if (!acpi_disabled)
+ lfa_remove_acpi(&sdev->dev);
clean_fw_components_tree();
flush_workqueue(fw_comps_update_wq);
destroy_workqueue(fw_comps_update_wq);
Regards,
Veda