FROMLIST: misc: fastrpc: Enable poll mode for specific devices

drivers/misc/fastrpc.c

@@ -260,6 +260,8 @@ struct fastrpc_invoke_ctx {
 	bool is_work_done;
 	/* response flags from remote processor */
 	enum fastrpc_response_flags rsp_flags;
+	/* process updates poll memory instead of glink response */
+	bool is_polled;
 	struct kref refcount;
 	struct list_head node; /* list of ctxs */
 	struct completion work;
@@ -304,6 +306,7 @@ struct fastrpc_channel_ctx {
 	bool secure;
 	bool unsigned_support;
 	u64 dma_mask;
+	bool poll_mode_supported;
 };
 
 struct fastrpc_device {
@@ -325,6 +328,8 @@ struct fastrpc_user {
 	int client_id;
 	int pd;
 	bool is_secure_dev;
+	/* Flags poll mode state */
+	bool poll_mode;
 	/* Lock for lists */
 	spinlock_t lock;
 	/* lock for allocations */
@@ -1268,28 +1273,15 @@ static int fastrpc_wait_for_completion(struct fastrpc_invoke_ctx *ctx,
 {
 	int err;
 
-	do {
-		switch (ctx->rsp_flags) {
-		case NORMAL_RESPONSE:
-			err = fastrpc_wait_for_response(ctx, kernel);
-			if (err || ctx->is_work_done)
-				return err;
-			break;
-		case POLL_MODE:
-			err = poll_for_remote_response(ctx);
-			/* If polling timed out, move to normal response mode */
-			if (err)
-				ctx->rsp_flags = NORMAL_RESPONSE;
-			break;
-		default:
-			err = -EBADR;
-			dev_dbg(ctx->fl->sctx->dev,
-				"unsupported response type:0x%x\n", ctx->rsp_flags);
-			break;
-		}
-	} while (!ctx->is_work_done);
+	if (ctx->is_polled) {
+		err = poll_for_remote_response(ctx);
+		if (!err)
+			return 0;
+		/* If polling timed out or failed, move to normal response mode */
+		ctx->is_polled = false;
+	}
 
-	return err;
+	return fastrpc_wait_for_response(ctx, kernel);
 }
 
 static int fastrpc_internal_invoke(struct fastrpc_user *fl,  u32 kernel,
@@ -1327,8 +1319,13 @@ static int fastrpc_internal_invoke(struct fastrpc_user *fl,  u32 kernel,
 	if (err)
 		goto bail;
 
-	if (handle > FASTRPC_MAX_STATIC_HANDLE && fl->pd == USER_PD)
-		ctx->rsp_flags = POLL_MODE;
+	/*
+	* Set message context as polled if the call is for a user PD
+	* dynamic module and user has enabled poll mode.
+	*/
+	if (handle > FASTRPC_MAX_STATIC_HANDLE && fl->pd == USER_PD &&
+	    fl->poll_mode)
+		ctx->is_polled = true;
 
 	err = fastrpc_wait_for_completion(ctx, kernel);
 	if (err)
@@ -1891,6 +1888,33 @@ static int fastrpc_get_info_from_kernel(struct fastrpc_ioctl_capability *cap,
 	return 0;
 }
 
+static int fastrpc_set_option(struct fastrpc_user *fl, char __user *argp)
+{
+	struct fastrpc_ioctl_set_option opt = { 0 };
+	int i;
+
+	if (copy_from_user(&opt, argp, sizeof(opt)))
+		return -EFAULT;
+
+	for (i = 0; i < ARRAY_SIZE(opt.reserved); i++) {
+		if (opt.reserved[i] != 0)
+			return -EINVAL;
+	}
+
+	if (opt.request_id != FASTRPC_POLL_MODE)
+		return -EINVAL;
+
+	if (opt.value) {
+		if (!fl->cctx->poll_mode_supported)
+			return -EOPNOTSUPP;
+		fl->poll_mode = true;
+	} else {
+		fl->poll_mode = false;
+	}
+
+	return 0;
+}
+
 static int fastrpc_get_dsp_info(struct fastrpc_user *fl, char __user *argp)
 {
 	struct fastrpc_ioctl_capability cap = {0};
@@ -2254,6 +2278,9 @@ static long fastrpc_device_ioctl(struct file *file, unsigned int cmd,
 	case FASTRPC_IOCTL_MEM_UNMAP:
 		err = fastrpc_req_mem_unmap(fl, argp);
 		break;
+	case FASTRPC_IOCTL_SET_OPTION:
+		err = fastrpc_set_option(fl, argp);
+		break;
 	case FASTRPC_IOCTL_GET_DSP_INFO:
 		err = fastrpc_get_dsp_info(fl, argp);
 		break;
@@ -2400,6 +2427,21 @@ static int fastrpc_get_domain_id(const char *domain)
 	return -EINVAL;
 }
 
+/*
+ * Exception list for legacy platforms whose DSP firmware supports
+ * FastRPC polling mode.
+ *
+ * NOTE: This list is intentionally closed.
+ * Do NOT add new platforms here. New SoCs must advertise polling mode
+ * support via their soc_data.
+ */
+
+static const char *const fastrpc_poll_supported_machines[] = {
+	"qcom,milos",	 "qcom,qcs8300",  "qcom,sa8775p", "qcom,sar2130p",
+	"qcom,sm8450",	 "qcom,sm8550",	  "qcom,sm8650",  "qcom,sm8750",
+	"qcom,x1e80100", "qcom,x1p42100", NULL,
+};
+
 static int fastrpc_rpmsg_probe(struct rpmsg_device *rpdev)
 {
 	struct device *rdev = &rpdev->dev;
@@ -2471,6 +2513,9 @@ static int fastrpc_rpmsg_probe(struct rpmsg_device *rpdev)
 	secure_dsp = !(of_property_read_bool(rdev->of_node, "qcom,non-secure-domain"));
 	data->secure = secure_dsp;
 
+	data->poll_mode_supported =
+		of_machine_compatible_match(fastrpc_poll_supported_machines);
+
 	switch (domain_id) {
 	case ADSP_DOMAIN_ID:
 	case MDSP_DOMAIN_ID:

include/uapi/misc/fastrpc.h

@@ -16,6 +16,7 @@
 #define FASTRPC_IOCTL_INIT_CREATE_STATIC _IOWR('R', 9, struct fastrpc_init_create_static)
 #define FASTRPC_IOCTL_MEM_MAP		_IOWR('R', 10, struct fastrpc_mem_map)
 #define FASTRPC_IOCTL_MEM_UNMAP		_IOWR('R', 11, struct fastrpc_mem_unmap)
+#define FASTRPC_IOCTL_SET_OPTION _IOWR('R', 12, struct fastrpc_ioctl_set_option)
 #define FASTRPC_IOCTL_GET_DSP_INFO	_IOWR('R', 13, struct fastrpc_ioctl_capability)
 
 /**
@@ -67,6 +68,24 @@ enum fastrpc_proc_attr {
 /* Fastrpc attribute for memory protection of buffers */
 #define FASTRPC_ATTR_SECUREMAP	(1)
 
+/**
+ * FASTRPC_POLL_MODE - Enable/disable poll mode for FastRPC invocations
+ *
+ * Poll mode is an optimization that allows the CPU to poll shared memory
+ * for completion instead of waiting for an interrupt-based response.
+ * This reduces latency for fast-completing operations.
+ *
+ * Restrictions:
+ * - Only supported for USER_PD (User Protection Domain)
+ * - Only applies to dynamic modules (handle > 20)
+ * - Static modules always use interrupt-based completion
+ *
+ * Values:
+ * - 0: Disable poll mode (use interrupt-based completion)
+ * - 1: Enable poll mode (poll shared memory for completion)
+ */
+#define FASTRPC_POLL_MODE (1)
+
 struct fastrpc_invoke_args {
 	__u64 ptr;
 	__u64 length;
@@ -133,6 +152,12 @@ struct fastrpc_mem_unmap {
 	__s32 reserved[5];
 };
 
+struct fastrpc_ioctl_set_option {
+	__u32 request_id; /* Request type (e.g., FASTRPC_POLL_MODE) */
+	__u32 value; /* Request-specific value */
+	__s32 reserved[6];
+};
+
 struct fastrpc_ioctl_capability {
 	__u32 unused; /* deprecated, ignored by the kernel */
 	__u32 attribute_id;