lib: Add dynamic registration of SBI extensions

This patch extends our SBI ecall implementation to allow
dynamic registration of various SBI extensions. Using this
dynamic registration we can break-up SBI ecall implementation
into multiple files and even register experimental/custom
SBI extensions from platform code.

Signed-off-by: Anup Patel <anup.patel@wdc.com>
Reviewed-by: Atish Patra <atish.patra@wdc.com>

include/sbi/sbi_ecall.h

@@ -11,15 +11,37 @@
 #define __SBI_ECALL_H__
 
 #include <sbi/sbi_types.h>
+#include <sbi/sbi_list.h>
 
 struct sbi_trap_regs;
+struct sbi_trap_info;
 struct sbi_scratch;
 
+struct sbi_ecall_extension {
+	struct sbi_dlist head;
+	unsigned long extid_start;
+	unsigned long extid_end;
+	int (* probe)(struct sbi_scratch *scratch,
+		      unsigned long extid, unsigned long *out_val);
+	int (* handle)(struct sbi_scratch *scratch,
+		       unsigned long extid, unsigned long funcid,
+		       unsigned long *args, unsigned long *out_val,
+		       struct sbi_trap_info *out_trap);
+};
+
 u16 sbi_ecall_version_major(void);
 
 u16 sbi_ecall_version_minor(void);
 
+struct sbi_ecall_extension *sbi_ecall_find_extension(unsigned long extid);
+
+int sbi_ecall_register_extension(struct sbi_ecall_extension *ext);
+
+void sbi_ecall_unregister_extension(struct sbi_ecall_extension *ext);
+
 int sbi_ecall_handler(u32 hartid, ulong mcause, struct sbi_trap_regs *regs,
 		      struct sbi_scratch *scratch);
 
+int sbi_ecall_init(void);
+
 #endif

lib/sbi/sbi_ecall.c

@@ -52,49 +52,29 @@ static int sbi_load_hart_mask_unpriv(struct sbi_scratch *scratch, ulong *pmask,
 	return 0;
 }
 
-int sbi_check_extension(struct sbi_scratch *scratch, unsigned long extid,
-			unsigned long *out_val)
+static int sbi_ecall_base_probe(struct sbi_scratch *scratch,
+				unsigned long extid,
+				unsigned long *out_val)
 {
-	/**
-	 * Each extension apart from base & 0.1, will be implemented as
-	 * platform specific feature. Thus, extension probing can be achieved
-	 * by checking the feature bits of the platform. We can create a map
-	 * between extension ID & feature and use a generic function to check
-	 * or just use a switch case for every new extension support added
-	 * TODO: Implement it.
-	 */
+	struct sbi_ecall_extension *ext;
 
-	if ((extid >= SBI_EXT_0_1_SET_TIMER && extid <= SBI_EXT_0_1_SHUTDOWN) ||
-	    (extid == SBI_EXT_BASE) ||
-	    (extid == SBI_EXT_TIME) ||
-	    (extid == SBI_EXT_IPI)  ||
-	    (extid == SBI_EXT_RFENCE)) {
-		*out_val = 1;
-	} else if (extid >= SBI_EXT_VENDOR_START &&
-		   extid <= SBI_EXT_VENDOR_END) {
-		*out_val = sbi_platform_vendor_ext_check(
-						sbi_platform_ptr(scratch),
-						extid);
-	} else
+	ext = sbi_ecall_find_extension(extid);
+	if (!ext) {
 		*out_val = 0;
+		return 0;
+	}
 
+	if (ext->probe)
+		return ext->probe(scratch, extid, out_val);
+
+	*out_val = 1;
 	return 0;
 }
 
-int sbi_ecall_vendor_ext_handler(struct sbi_scratch *scratch,
-				 unsigned long extid, unsigned long funcid,
-				 unsigned long *args, unsigned long *out_val,
-				 struct sbi_trap_info *out_trap)
-{
-	return sbi_platform_vendor_ext_provider(sbi_platform_ptr(scratch),
-						extid, funcid, args,
-						out_val, out_trap);
-}
-
-int sbi_ecall_base_handler(struct sbi_scratch *scratch,
-			   unsigned long extid, unsigned long funcid,
-			   unsigned long *args, unsigned long *out_val,
-			   struct sbi_trap_info *out_trap)
+static int sbi_ecall_base_handler(struct sbi_scratch *scratch,
+				  unsigned long extid, unsigned long funcid,
+				  unsigned long *args, unsigned long *out_val,
+				  struct sbi_trap_info *out_trap)
 {
 	int ret = 0;
 
@@ -122,7 +102,7 @@ int sbi_ecall_base_handler(struct sbi_scratch *scratch,
 		*out_val = csr_read(CSR_MIMPID);
 		break;
 	case SBI_EXT_BASE_PROBE_EXT:
-		ret = sbi_check_extension(scratch, args[0], out_val);
+		ret = sbi_ecall_base_probe(scratch, args[0], out_val);
 		break;
 	default:
 		ret = SBI_ENOTSUPP;
@@ -131,8 +111,16 @@ int sbi_ecall_base_handler(struct sbi_scratch *scratch,
 	return ret;
 }
 
-int sbi_ecall_time_handler(struct sbi_scratch *scratch, unsigned long funcid,
-			   unsigned long *args)
+static struct sbi_ecall_extension ecall_base = {
+	.extid_start = SBI_EXT_BASE,
+	.extid_end = SBI_EXT_BASE,
+	.handle = sbi_ecall_base_handler,
+};
+
+static int sbi_ecall_time_handler(struct sbi_scratch *scratch,
+				  unsigned long extid, unsigned long funcid,
+				  unsigned long *args, unsigned long *out_val,
+				  struct sbi_trap_info *out_trap)
 {
 	int ret = 0;
 
@@ -149,8 +137,16 @@ int sbi_ecall_time_handler(struct sbi_scratch *scratch, unsigned long funcid,
 	return ret;
 }
 
-int sbi_ecall_ipi_handler(struct sbi_scratch *scratch, unsigned long funcid,
-			   unsigned long *args, unsigned long *tval)
+static struct sbi_ecall_extension ecall_time = {
+	.extid_start = SBI_EXT_TIME,
+	.extid_end = SBI_EXT_TIME,
+	.handle = sbi_ecall_time_handler,
+};
+
+static int sbi_ecall_ipi_handler(struct sbi_scratch *scratch,
+				 unsigned long extid, unsigned long funcid,
+				 unsigned long *args, unsigned long *out_val,
+				 struct sbi_trap_info *out_trap)
 {
 	int ret = 0;
 
@@ -162,8 +158,16 @@ int sbi_ecall_ipi_handler(struct sbi_scratch *scratch, unsigned long funcid,
 	return ret;
 }
 
-int sbi_ecall_rfence_handler(struct sbi_scratch *scratch, unsigned long funcid,
-			   unsigned long *args, unsigned long *tval)
+static struct sbi_ecall_extension ecall_ipi = {
+	.extid_start = SBI_EXT_IPI,
+	.extid_end = SBI_EXT_IPI,
+	.handle = sbi_ecall_ipi_handler,
+};
+
+static int sbi_ecall_rfence_handler(struct sbi_scratch *scratch,
+				    unsigned long extid, unsigned long funcid,
+				    unsigned long *args, unsigned long *out_val,
+				    struct sbi_trap_info *out_trap)
 {
 	int ret = 0;
 	struct sbi_tlb_info tlb_info;
@@ -235,8 +239,16 @@ int sbi_ecall_rfence_handler(struct sbi_scratch *scratch, unsigned long funcid,
 	return ret;
 }
 
-int sbi_ecall_0_1_handler(struct sbi_scratch *scratch, unsigned long extid,
-			   unsigned long *args, struct sbi_trap_info *out_trap)
+static struct sbi_ecall_extension ecall_rfence = {
+	.extid_start = SBI_EXT_RFENCE,
+	.extid_end = SBI_EXT_RFENCE,
+	.handle = sbi_ecall_rfence_handler,
+};
+
+static int sbi_ecall_0_1_handler(struct sbi_scratch *scratch,
+				 unsigned long extid, unsigned long funcid,
+				 unsigned long *args, unsigned long *out_val,
+				 struct sbi_trap_info *out_trap)
 {
 	int ret = 0;
 	struct sbi_tlb_info tlb_info;
@@ -308,10 +320,92 @@ int sbi_ecall_0_1_handler(struct sbi_scratch *scratch, unsigned long extid,
 	return ret;
 }
 
+static struct sbi_ecall_extension ecall_0_1 = {
+	.extid_start = SBI_EXT_0_1_SET_TIMER,
+	.extid_end = SBI_EXT_0_1_SHUTDOWN,
+	.handle = sbi_ecall_0_1_handler,
+};
+
+static int sbi_ecall_vendor_probe(struct sbi_scratch *scratch,
+				  unsigned long extid,
+				  unsigned long *out_val)
+{
+	*out_val = sbi_platform_vendor_ext_check(sbi_platform_ptr(scratch),
+						 extid);
+	return 0;
+}
+
+static int sbi_ecall_vendor_handler(struct sbi_scratch *scratch,
+				    unsigned long extid, unsigned long funcid,
+				    unsigned long *args, unsigned long *out_val,
+				    struct sbi_trap_info *out_trap)
+{
+	return sbi_platform_vendor_ext_provider(sbi_platform_ptr(scratch),
+						extid, funcid, args,
+						out_val, out_trap);
+}
+
+static struct sbi_ecall_extension ecall_vendor = {
+	.extid_start = SBI_EXT_VENDOR_START,
+	.extid_end = SBI_EXT_VENDOR_END,
+	.probe = sbi_ecall_vendor_probe,
+	.handle = sbi_ecall_vendor_handler,
+};
+
+static SBI_LIST_HEAD(ecall_exts_list);
+
+struct sbi_ecall_extension *sbi_ecall_find_extension(unsigned long extid)
+{
+	struct sbi_ecall_extension *t, *ret = NULL;
+
+	sbi_list_for_each_entry(t, &ecall_exts_list, head) {
+		if (t->extid_start <= extid && extid <= t->extid_end) {
+			ret = t;
+			break;
+		}
+	}
+
+	return ret;
+}
+
+int sbi_ecall_register_extension(struct sbi_ecall_extension *ext)
+{
+	if (!ext || (ext->extid_end < ext->extid_start) || !ext->handle)
+		return SBI_EINVAL;
+	if (sbi_ecall_find_extension(ext->extid_start) ||
+	    sbi_ecall_find_extension(ext->extid_end))
+		return SBI_EINVAL;
+
+	SBI_INIT_LIST_HEAD(&ext->head);
+	sbi_list_add_tail(&ext->head, &ecall_exts_list);
+
+	return 0;
+}
+
+void sbi_ecall_unregister_extension(struct sbi_ecall_extension *ext)
+{
+	bool found = FALSE;
+	struct sbi_ecall_extension *t;
+
+	if (!ext)
+		return;
+
+	sbi_list_for_each_entry(t, &ecall_exts_list, head) {
+		if (t == ext) {
+			found = TRUE;
+			break;
+		}
+	}
+
+	if (found)
+		sbi_list_del_init(&ext->head);
+}
+
 int sbi_ecall_handler(u32 hartid, ulong mcause, struct sbi_trap_regs *regs,
 		      struct sbi_scratch *scratch)
 {
 	int ret = 0;
+	struct sbi_ecall_extension *ext;
 	unsigned long extension_id = regs->a7;
 	unsigned long func_id = regs->a6;
 	struct sbi_trap_info trap = {0};
@@ -326,26 +420,13 @@ int sbi_ecall_handler(u32 hartid, ulong mcause, struct sbi_trap_regs *regs,
 	args[4] = regs->a4;
 	args[5] = regs->a5;
 
-	if (extension_id >= SBI_EXT_0_1_SET_TIMER &&
-	    extension_id <= SBI_EXT_0_1_SHUTDOWN) {
-		ret = sbi_ecall_0_1_handler(scratch, extension_id,
-					    args, &trap);
-		is_0_1_spec = 1;
-	} else if (extension_id == SBI_EXT_BASE)
-		ret = sbi_ecall_base_handler(scratch, extension_id, func_id,
-					     args, &out_val, &trap);
-	else if (extension_id == SBI_EXT_TIME)
-		ret = sbi_ecall_time_handler(scratch, func_id, args);
-	else if (extension_id == SBI_EXT_IPI)
-		ret = sbi_ecall_ipi_handler(scratch, func_id, args, &out_val);
-	else if (extension_id == SBI_EXT_RFENCE)
-		ret = sbi_ecall_rfence_handler(scratch, func_id,
-					       args, &out_val);
-	else if (extension_id >= SBI_EXT_VENDOR_START &&
-		extension_id <= SBI_EXT_VENDOR_END) {
-		ret = sbi_ecall_vendor_ext_handler(scratch, extension_id,
-						   func_id, args, &out_val,
-						   &trap);
+	ext = sbi_ecall_find_extension(extension_id);
+	if (ext && ext->handle) {
+		ret = ext->handle(scratch, extension_id, func_id,
+				  args, &out_val, &trap);
+		if (extension_id >= SBI_EXT_0_1_SET_TIMER &&
+		    extension_id <= SBI_EXT_0_1_SHUTDOWN)
+			is_0_1_spec = 1;
 	} else {
 		ret = SBI_ENOTSUPP;
 	}
@@ -369,3 +450,30 @@ int sbi_ecall_handler(u32 hartid, ulong mcause, struct sbi_trap_regs *regs,
 
 	return 0;
 }
+
+int sbi_ecall_init(void)
+{
+	int ret;
+
+	/* The order of below registrations is performance optimized */
+	ret = sbi_ecall_register_extension(&ecall_time);
+	if (ret)
+		return ret;
+	ret = sbi_ecall_register_extension(&ecall_rfence);
+	if (ret)
+		return ret;
+	ret = sbi_ecall_register_extension(&ecall_ipi);
+	if (ret)
+		return ret;
+	ret = sbi_ecall_register_extension(&ecall_base);
+	if (ret)
+		return ret;
+	ret = sbi_ecall_register_extension(&ecall_0_1);
+	if (ret)
+		return ret;
+	ret = sbi_ecall_register_extension(&ecall_vendor);
+	if (ret)
+		return ret;
+
+	return 0;
+}

lib/sbi/sbi_init.c

@@ -112,6 +112,10 @@ static void __noreturn init_coldboot(struct sbi_scratch *scratch, u32 hartid)
 	if (rc)
 		sbi_hart_hang();
 
+	rc = sbi_ecall_init();
+	if (rc)
+		sbi_hart_hang();
+
 	rc = sbi_system_final_init(scratch, TRUE);
 	if (rc)
 		sbi_hart_hang();