Add aie4_set_ctx_hysteresis() to configure the AIE4 context switch
hysteresis timeout via the SET_RUNTIME_CONFIG message, applied at hw
start (PF and classic paths) with a default of 1000 us.

Expose a debugfs node 'ctx_switch_hysteresis_us' to change the timeout
at runtime (0 disables hysteresis). The stored value is re-applied on
every hw start so it survives runtime suspend/resume.

Co-developed-by: Nishad Saraf <[email protected]>
Signed-off-by: Nishad Saraf <[email protected]>
Signed-off-by: David Zhang <[email protected]>
---
 drivers/accel/amdxdna/aie4_message.c    | 50 +++++++++++++++
 drivers/accel/amdxdna/aie4_msg_priv.h   | 36 +++++++++++
 drivers/accel/amdxdna/aie4_pci.c        | 85 ++++++++++++++++++++++++-
 drivers/accel/amdxdna/aie4_pci.h        | 12 ++++
 drivers/accel/amdxdna/amdxdna_debugfs.c |  3 +
 drivers/accel/amdxdna/amdxdna_pci_drv.h |  1 +
 6 files changed, 185 insertions(+), 2 deletions(-)

diff --git a/drivers/accel/amdxdna/aie4_message.c 
b/drivers/accel/amdxdna/aie4_message.c
index d48ef855fee7..1bddcb183db6 100644
--- a/drivers/accel/amdxdna/aie4_message.c
+++ b/drivers/accel/amdxdna/aie4_message.c
@@ -248,3 +248,53 @@ int aie4_msg_set_power_mode(struct amdxdna_dev_hdl *ndev, 
u8 power_mode)
 
        return ret;
 }
+
+int aie4_set_runtime_cfg(struct amdxdna_dev_hdl *ndev, u32 type,
+                        const void *data, size_t size)
+{
+       DECLARE_AIE_MSG(aie4_msg_set_runtime_cfg, 
AIE4_MSG_OP_SET_RUNTIME_CONFIG);
+       u8 buf[sizeof(req.type) + AIE4_RUNTIME_CFG_MAX_DATA_SIZE] = { 0 };
+       int ret;
+
+       if (size > AIE4_RUNTIME_CFG_MAX_DATA_SIZE)
+               return -EINVAL;
+
+       /*
+        * Firmware expects a 4-byte @type immediately followed by the
+        * per-type payload (size validated against the struct npu_msg_-
+        * runtime_config_* picked by @type). The shared request struct
+        * carries an inline @data[4] slot, so stage only the 4-byte @type
+        * header plus the variable payload contiguously and send exactly
+        * that many bytes on the wire.
+        */
+       req.type = type;
+       memcpy(buf, &req.type, sizeof(req.type));
+       memcpy(buf + sizeof(req.type), data, size);
+
+       msg.send_data = buf;
+       msg.send_size = sizeof(req.type) + size;
+
+       ret = aie_send_mgmt_msg_wait(&ndev->aie, &msg);
+       if (ret)
+               XDNA_ERR(ndev->aie.xdna, "Failed to set runtime cfg %u: %d", 
type, ret);
+       return ret;
+}
+
+int aie4_set_ctx_hysteresis(struct amdxdna_dev_hdl *ndev, u32 timeout_us)
+{
+       struct aie4_msg_runtime_config_ctx_switch_hysteresis cfg = {
+               .timeout_us = timeout_us,
+       };
+       int ret;
+
+       ret = aie4_set_runtime_cfg(ndev, 
AIE4_RUNTIME_CONFIG_CTX_SWITCH_HYSTERESIS,
+                                  &cfg, sizeof(cfg));
+       if (ret)
+               XDNA_WARN(ndev->aie.xdna,
+                         "Failed to set ctx switch hysteresis to %u us (%d), 
using fw default",
+                         timeout_us, ret);
+       else
+               XDNA_DBG(ndev->aie.xdna, "Context switch hysteresis set to %u 
us", timeout_us);
+
+       return ret;
+}
diff --git a/drivers/accel/amdxdna/aie4_msg_priv.h 
b/drivers/accel/amdxdna/aie4_msg_priv.h
index fe78df9e23c8..77984683a7b6 100644
--- a/drivers/accel/amdxdna/aie4_msg_priv.h
+++ b/drivers/accel/amdxdna/aie4_msg_priv.h
@@ -12,6 +12,7 @@
 enum aie4_msg_opcode {
        AIE4_MSG_OP_IDENTIFY                         = 0x10002,
        AIE4_MSG_OP_SUSPEND                          = 0x10003,
+       AIE4_MSG_OP_SET_RUNTIME_CONFIG               = 0x10007,
        AIE4_MSG_OP_QUERY_CERT_FIRMWARE_VERSION      = 0x1000F,
 
        AIE4_MSG_OP_CREATE_VFS                       = 0x20001,
@@ -65,6 +66,41 @@ struct aie4_msg_suspend_resp {
        enum aie4_msg_status status;
 } __packed;
 
+/*
+ * Type selector for AIE4_MSG_OP_SET_RUNTIME_CONFIG. Values match the firmware
+ * ABI enum npu_msg_runtime_config_type; only the configs the driver programs
+ * are enumerated here.
+ */
+enum aie4_msg_runtime_config_type {
+       AIE4_RUNTIME_CONFIG_CTX_SWITCH_HYSTERESIS       = 0xD,
+       AIE4_MAX_RUNTIME_CONFIG
+};
+
+struct aie4_msg_set_runtime_cfg_req {
+       __u32 type;
+       __u8 data[4];
+} __packed;
+
+struct aie4_msg_set_runtime_cfg_resp {
+       enum aie4_msg_status status;
+} __packed;
+
+/* Maximum trailing per-type payload (struct npu_msg_runtime_config_*) in the
+ * firmware ABI; today the largest is npu_msg_runtime_config_event_trace_status
+ * at 12 bytes. Rounded up to leave headroom for future configs.
+ */
+#define AIE4_RUNTIME_CFG_MAX_DATA_SIZE 16
+
+/*
+ * Context switch hysteresis configuration.
+ *
+ * @timeout_us: Hysteresis time in microseconds for keeping a context loaded
+ *              in the AIE after it becomes idle, or 0 to disable hysteresis.
+ */
+struct aie4_msg_runtime_config_ctx_switch_hysteresis {
+       __u32 timeout_us;
+} __packed;
+
 struct aie4_msg_create_vfs_req {
        __u32 vf_cnt;
 } __packed;
diff --git a/drivers/accel/amdxdna/aie4_pci.c b/drivers/accel/amdxdna/aie4_pci.c
index 95e682a3a4b7..60348ec5bc53 100644
--- a/drivers/accel/amdxdna/aie4_pci.c
+++ b/drivers/accel/amdxdna/aie4_pci.c
@@ -5,8 +5,10 @@
 
 #include <drm/amdxdna_accel.h>
 #include <drm/drm_drv.h>
+#include <drm/drm_file.h>
 #include <drm/drm_managed.h>
 #include <drm/drm_print.h>
+#include <linux/debugfs.h>
 #include <linux/firmware.h>
 #include <linux/sizes.h>
 
@@ -325,6 +327,20 @@ int aie4_restore_power_mode(struct amdxdna_dev_hdl *ndev)
        return aie4_msg_set_power_mode(ndev, ndev->pw_mode);
 }
 
+static int aie4_config_fw(struct amdxdna_dev_hdl *ndev)
+{
+       int ret;
+
+       ret = aie4_attach_work_buffer(ndev);
+       if (ret)
+               return ret;
+
+       /* Best-effort tuning knob; failure is warned inside and does not fail 
hw start */
+       aie4_set_ctx_hysteresis(ndev, ndev->ctx_switch_hysteresis_us);
+
+       return 0;
+}
+
 static int aie4_pf_hw_start(struct amdxdna_dev_hdl *ndev)
 {
        int ret;
@@ -337,7 +353,7 @@ static int aie4_pf_hw_start(struct amdxdna_dev_hdl *ndev)
        if (ret)
                goto stop_fw;
 
-       ret = aie4_attach_work_buffer(ndev);
+       ret = aie4_config_fw(ndev);
        if (ret)
                goto mbox_fini;
 
@@ -419,7 +435,7 @@ static int aie4_classic_hw_start(struct amdxdna_dev_hdl 
*ndev)
        if (ret)
                goto mailbox_fini;
 
-       ret = aie4_attach_work_buffer(ndev);
+       ret = aie4_config_fw(ndev);
        if (ret)
                goto mailbox_fini;
 
@@ -574,6 +590,7 @@ static int aie4m_pcidev_init(struct amdxdna_dev *xdna)
 
        ndev->priv = xdna->dev_info->dev_priv;
        ndev->aie.xdna = xdna;
+       ndev->ctx_switch_hysteresis_us = AIE4_CTX_HYSTERESIS_US;
        ndev->pw_mode = POWER_MODE_DEFAULT;
        xdna->dev_handle = ndev;
 
@@ -921,15 +938,78 @@ static void aie4_classic_fini(struct amdxdna_dev *xdna)
        aie4_free_work_buffer(xdna->dev_handle);
 }
 
+static int aie4_ctx_hysteresis_get(void *data, u64 *val)
+{
+       struct amdxdna_dev_hdl *ndev = data;
+       struct amdxdna_dev *xdna = ndev->aie.xdna;
+
+       guard(mutex)(&xdna->dev_lock);
+       *val = ndev->ctx_switch_hysteresis_us;
+
+       return 0;
+}
+
+static int aie4_ctx_hysteresis_set(void *data, u64 val)
+{
+       struct amdxdna_dev_hdl *ndev = data;
+       struct amdxdna_dev *xdna = ndev->aie.xdna;
+       int ret, idx;
+
+       if (val > U32_MAX)
+               return -EINVAL;
+
+       if (!drm_dev_enter(&xdna->ddev, &idx))
+               return -ENODEV;
+
+       mutex_lock(&xdna->dev_lock);
+
+       ret = amdxdna_pm_resume_get_locked(xdna);
+       if (ret)
+               goto unlock;
+
+       ret = aie4_set_ctx_hysteresis(ndev, (u32)val);
+       if (!ret)
+               ndev->ctx_switch_hysteresis_us = (u32)val;
+
+       amdxdna_pm_suspend_put(xdna);
+
+unlock:
+       mutex_unlock(&xdna->dev_lock);
+       drm_dev_exit(idx);
+
+       return ret;
+}
+
+/* Context switch hysteresis timeout in microseconds; 0 disables hysteresis. */
+DEFINE_DEBUGFS_ATTRIBUTE(aie4_ctx_hysteresis_fops, aie4_ctx_hysteresis_get,
+                        aie4_ctx_hysteresis_set, "%llu\n");
+
+static void aie4_debugfs_init(struct amdxdna_dev *xdna)
+{
+       struct amdxdna_dev_hdl *ndev = xdna->dev_handle;
+
+       /*
+        * Context switch hysteresis is a system-control runtime config that is
+        * only programmed on the PF/classic hw start paths, never on a VF.
+        * Only expose the knob where the driver actually applies it.
+        */
+       if (!to_pci_dev(xdna->ddev.dev)->is_virtfn)
+               debugfs_create_file_unsafe("ctx_switch_hysteresis_us", 0600,
+                                          xdna->ddev.accel->debugfs_root, ndev,
+                                          &aie4_ctx_hysteresis_fops);
+}
+
 const struct amdxdna_dev_ops aie4_pf_ops = {
        .init                   = aie4_pf_init,
        .fini                   = aie4_pf_fini,
+       .debugfs_init           = aie4_debugfs_init,
        .sriov_configure        = aie4_sriov_configure,
 };
 
 const struct amdxdna_dev_ops aie4_vf_ops = {
        .init                   = aie4_vf_init,
        .fini                   = aie4_vf_fini,
+       .debugfs_init           = aie4_debugfs_init,
        .hwctx_init             = aie4_hwctx_init,
        .hwctx_fini             = aie4_hwctx_fini,
        .cmd_wait               = aie4_cmd_wait,
@@ -940,6 +1020,7 @@ const struct amdxdna_dev_ops aie4_vf_ops = {
 const struct amdxdna_dev_ops aie4_classic_ops = {
        .init                   = aie4_classic_init,
        .fini                   = aie4_classic_fini,
+       .debugfs_init           = aie4_debugfs_init,
        .hwctx_init             = aie4_hwctx_init,
        .hwctx_fini             = aie4_hwctx_fini,
        .cmd_wait               = aie4_cmd_wait,
diff --git a/drivers/accel/amdxdna/aie4_pci.h b/drivers/accel/amdxdna/aie4_pci.h
index 6e9e7f874a44..063cedfe3c9d 100644
--- a/drivers/accel/amdxdna/aie4_pci.h
+++ b/drivers/accel/amdxdna/aie4_pci.h
@@ -14,6 +14,9 @@
 #include "aie4_msg_priv.h"
 #include "amdxdna_mailbox.h"
 
+/* Default context switch hysteresis timeout in microseconds. */
+#define AIE4_CTX_HYSTERESIS_US 1000
+
 struct cert_comp {
        struct amdxdna_dev_hdl          *ndev;
        u32                             msix_idx;
@@ -69,6 +72,12 @@ struct amdxdna_dev_hdl {
 
        u8                              pw_mode;
 
+       /*
+        * Context switch hysteresis timeout in microseconds; pushed to the
+        * firmware at hw start and tunable at runtime via debugfs.
+        */
+       u32                             ctx_switch_hysteresis_us;
+
        struct amdxdna_drm_query_firmware_version cert_version;
 };
 
@@ -92,6 +101,9 @@ int aie4_init_dpm_freq_table(struct amdxdna_dev_hdl *ndev);
 int aie4_query_dpm_level(struct amdxdna_dev_hdl *ndev,
                         u32 *aieclk_dpm_level, u32 *npuhclk_dpm_level);
 int aie4_msg_set_power_mode(struct amdxdna_dev_hdl *ndev, u8 power_mode);
+int aie4_set_runtime_cfg(struct amdxdna_dev_hdl *ndev, u32 type,
+                        const void *data, size_t size);
+int aie4_set_ctx_hysteresis(struct amdxdna_dev_hdl *ndev, u32 timeout_us);
 u32 aie4_msg_pasid(struct amdxdna_client *client);
 
 /* aie4_ctx.c */
diff --git a/drivers/accel/amdxdna/amdxdna_debugfs.c 
b/drivers/accel/amdxdna/amdxdna_debugfs.c
index a6ec17c63629..1f63cc91b168 100644
--- a/drivers/accel/amdxdna/amdxdna_debugfs.c
+++ b/drivers/accel/amdxdna/amdxdna_debugfs.c
@@ -126,4 +126,7 @@ void amdxdna_debugfs_init(struct amdxdna_dev *xdna)
                                    xdna,
                                    amdxdna_dbgfs_files[i].fops);
        }
+
+       if (xdna->dev_info->ops->debugfs_init)
+               xdna->dev_info->ops->debugfs_init(xdna);
 }
diff --git a/drivers/accel/amdxdna/amdxdna_pci_drv.h 
b/drivers/accel/amdxdna/amdxdna_pci_drv.h
index 953bf783b3f7..11f46ec738d7 100644
--- a/drivers/accel/amdxdna/amdxdna_pci_drv.h
+++ b/drivers/accel/amdxdna/amdxdna_pci_drv.h
@@ -54,6 +54,7 @@ struct amdxdna_sched_job;
 struct amdxdna_dev_ops {
        int (*init)(struct amdxdna_dev *xdna);
        void (*fini)(struct amdxdna_dev *xdna);
+       void (*debugfs_init)(struct amdxdna_dev *xdna);
        int (*resume)(struct amdxdna_dev *xdna);
        int (*suspend)(struct amdxdna_dev *xdna);
        int (*sriov_configure)(struct amdxdna_dev *xdna, int num_vfs);
-- 
2.34.1

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