[PATCH v1 2/2] cache: add SMCCC-backed cache invalidate provider
Srirangan Madhavan
smadhavan at nvidia.com
Tue Jun 2 01:21:45 PDT 2026
Add a cache maintenance provider for the Arm SMCCC cache clean+invalidate
interface.
The provider discovers SMCCC support and attributes at init time,
serializes firmware calls, handles transient BUSY and RATE_LIMITED
responses with bounded retries, and registers with the generic cache
coherency framework used by memregion callers.
Signed-off-by: Srirangan Madhavan <smadhavan at nvidia.com>
---
drivers/cache/Kconfig | 11 +++
drivers/cache/Makefile | 1 +
drivers/cache/arm_smccc_cache.c | 160 ++++++++++++++++++++++++++++++++
3 files changed, 172 insertions(+)
create mode 100644 drivers/cache/arm_smccc_cache.c
diff --git a/drivers/cache/Kconfig b/drivers/cache/Kconfig
index 1518449d47b5..5d7ef3d15979 100644
--- a/drivers/cache/Kconfig
+++ b/drivers/cache/Kconfig
@@ -42,6 +42,17 @@ menuconfig CACHEMAINT_FOR_HOTPLUG
if CACHEMAINT_FOR_HOTPLUG
+config ARM_SMCCC_CACHE
+ bool "Arm SMCCC cache maintenance provider"
+ depends on ARM64 && HAVE_ARM_SMCCC_DISCOVERY
+ help
+ Enable support for the Arm SMCCC cache clean+invalidate
+ interface as a provider for memory hotplug-like cache
+ maintenance operations.
+ The provider registers only when firmware advertises the
+ SMCCC calls and attributes, so systems without firmware support
+ continue without a registered provider.
+
config HISI_SOC_HHA
tristate "HiSilicon Hydra Home Agent (HHA) device driver"
depends on (ARM64 && ACPI) || COMPILE_TEST
diff --git a/drivers/cache/Makefile b/drivers/cache/Makefile
index b3362b15d6c1..6d91085aafe4 100644
--- a/drivers/cache/Makefile
+++ b/drivers/cache/Makefile
@@ -4,4 +4,5 @@ obj-$(CONFIG_AX45MP_L2_CACHE) += ax45mp_cache.o
obj-$(CONFIG_SIFIVE_CCACHE) += sifive_ccache.o
obj-$(CONFIG_STARFIVE_STARLINK_CACHE) += starfive_starlink_cache.o
+obj-$(CONFIG_ARM_SMCCC_CACHE) += arm_smccc_cache.o
obj-$(CONFIG_HISI_SOC_HHA) += hisi_soc_hha.o
diff --git a/drivers/cache/arm_smccc_cache.c b/drivers/cache/arm_smccc_cache.c
new file mode 100644
index 000000000000..ff6bca91a1a1
--- /dev/null
+++ b/drivers/cache/arm_smccc_cache.c
@@ -0,0 +1,160 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2026 NVIDIA Corporation
+ *
+ * Arm SMCCC cache maintenance provider using cache clean+invalidate calls.
+ */
+
+#include <linux/arm-smccc.h>
+#include <linux/cache_coherency.h>
+#include <linux/cleanup.h>
+#include <linux/delay.h>
+#include <linux/errno.h>
+#include <linux/init.h>
+#include <linux/kernel.h>
+#include <linux/mutex.h>
+#include <linux/nmi.h>
+
+#define SMCCC_CACHE_MAX_RETRIES 5
+#define SMCCC_CACHE_DEFAULT_DELAY_US 1000UL
+#define SMCCC_CACHE_MAX_DELAY_US 20000UL
+
+struct smccc_cache {
+ /* Must be first member */
+ struct cache_coherency_ops_inst cci;
+ struct mutex lock; /* Serializes SMCCC cache maintenance calls. */
+ u32 latency_us;
+ u32 rate_limit;
+};
+
+static int smccc_cache_status_to_errno(s32 status)
+{
+ switch (status) {
+ case SMCCC_RET_SUCCESS:
+ return 0;
+ case SMCCC_RET_NOT_SUPPORTED:
+ return -EOPNOTSUPP;
+ case SMCCC_RET_INVALID_PARAMETER:
+ return -EINVAL;
+ case SMCCC_RET_RATE_LIMITED:
+ return -EAGAIN;
+ case SMCCC_RET_BUSY:
+ return -EBUSY;
+ default:
+ return -EIO;
+ }
+}
+
+static unsigned long smccc_cache_delay_us(const struct smccc_cache *cache)
+{
+ unsigned long delay_us = 0;
+
+ if (cache->rate_limit)
+ delay_us = DIV_ROUND_UP_ULL(USEC_PER_SEC, cache->rate_limit);
+
+ if (cache->latency_us)
+ delay_us = max(delay_us, (unsigned long)cache->latency_us);
+
+ /*
+ * Firmware may advertise neither a rate limit nor a latency hint; use
+ * a small bounded backoff instead of retrying in a tight loop.
+ */
+ if (!delay_us)
+ delay_us = SMCCC_CACHE_DEFAULT_DELAY_US;
+
+ return min(delay_us, SMCCC_CACHE_MAX_DELAY_US);
+}
+
+static int smccc_cache_wbinv(struct cache_coherency_ops_inst *cci,
+ struct cc_inval_params *invp)
+{
+ struct smccc_cache *cache = container_of(cci, struct smccc_cache, cci);
+ struct arm_smccc_res res = {};
+ unsigned long delay_us = smccc_cache_delay_us(cache);
+ int ret;
+
+ if (!invp->size)
+ return -EINVAL;
+
+ /*
+ * Serialize the full retry sequence. With the default bounds, a caller
+ * may hold the mutex across up to four 20ms backoff sleeps.
+ */
+ guard(mutex)(&cache->lock);
+
+ for (unsigned int i = 0; i < SMCCC_CACHE_MAX_RETRIES; i++) {
+ /* Long firmware operations can trigger watchdog checks. */
+ touch_nmi_watchdog();
+
+ arm_smccc_1_1_invoke(ARM_SMCCC_ARCH_CLEAN_INV_MEMREGION,
+ invp->addr, invp->size, 0UL, &res);
+
+ ret = smccc_cache_status_to_errno((s32)res.a0);
+ if (!ret)
+ return 0;
+
+ if (ret != -EBUSY && ret != -EAGAIN)
+ return ret;
+
+ if (i + 1 == SMCCC_CACHE_MAX_RETRIES)
+ break;
+
+ fsleep(delay_us);
+ }
+
+ return -EBUSY;
+}
+
+static const struct cache_coherency_ops smccc_cache_ops = {
+ .wbinv = smccc_cache_wbinv,
+};
+
+static int __init smccc_cache_init(void)
+{
+ struct smccc_cache *cache;
+ struct arm_smccc_res res = {};
+ int ret;
+
+ if (arm_smccc_get_version() < ARM_SMCCC_VERSION_1_1)
+ return -ENODEV;
+
+ if (arm_smccc_1_1_get_conduit() == SMCCC_CONDUIT_NONE)
+ return -ENODEV;
+
+ arm_smccc_1_1_invoke(ARM_SMCCC_ARCH_FEATURES_FUNC_ID,
+ ARM_SMCCC_ARCH_CLEAN_INV_MEMREGION, &res);
+ if ((s32)res.a0 < 0)
+ return -ENODEV;
+
+ arm_smccc_1_1_invoke(ARM_SMCCC_ARCH_FEATURES_FUNC_ID,
+ ARM_SMCCC_ARCH_CLEAN_INV_MEMREGION_ATTRIBUTES,
+ &res);
+ if ((s32)res.a0 < 0)
+ return -ENODEV;
+
+ arm_smccc_1_1_invoke(ARM_SMCCC_ARCH_CLEAN_INV_MEMREGION_ATTRIBUTES,
+ &res);
+ if ((s32)res.a0)
+ return -ENODEV;
+
+ cache = cache_coherency_ops_instance_alloc(&smccc_cache_ops,
+ struct smccc_cache, cci);
+ if (!cache)
+ return -ENOMEM;
+
+ mutex_init(&cache->lock);
+ cache->latency_us = lower_32_bits(res.a2);
+ cache->rate_limit = lower_32_bits(res.a3);
+
+ ret = cache_coherency_ops_instance_register(&cache->cci);
+ if (ret) {
+ mutex_destroy(&cache->lock);
+ cache_coherency_ops_instance_put(&cache->cci);
+ return ret;
+ }
+
+ pr_info("SMCCC cache clean+invalidate provider registered\n");
+
+ return 0;
+}
+arch_initcall(smccc_cache_init);
--
2.43.0
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