@@ -1,3 +1,4 @@
 # SPDX-License-Identifier: ISC
 obj-$(CONFIG_NET_DSA_YT921X) += yt921x.o
 yt921x-objs := chip.o
+yt921x-objs += smi.o

@@ -13,7 +13,6 @@
 #include <linux/if_bridge.h>
 #include <linux/if_hsr.h>
 #include <linux/if_vlan.h>
-#include <linux/iopoll.h>
 #include <linux/mdio.h>
 #include <linux/module.h>
 #include <linux/of.h>

@@ -27,6 +26,7 @@
 #include <net/pkt_cls.h>
 
 #include "chip.h"
+#include "smi.h"
 
 struct yt921x_mib_desc {
 	unsigned int size;

@@ -155,9 +155,6 @@ static const struct yt921x_info yt921x_infos[] = {
 
 #define YT921X_VID_UNWARE	4095
 
-#define YT921X_POLL_SLEEP_US	10000
-#define YT921X_POLL_TIMEOUT_US	100000
-
 /* The interval should be small enough to avoid overflow of 32bit MIBs.
  *
  * Until we can read MIBs from stats64 call directly (i.e. sleep

@@ -196,208 +193,6 @@ static u32 ethaddr_lo2_to_u32(const unsigned char *addr)
 	return (addr[4] << 8) | addr[5];
 }
 
-static int yt921x_reg_read(struct yt921x_priv *priv, u32 reg, u32 *valp)
-{
-	WARN_ON(!mutex_is_locked(&priv->reg_lock));
-
-	return priv->reg_ops->read(priv->reg_ctx, reg, valp);
-}
-
-static int yt921x_reg_write(struct yt921x_priv *priv, u32 reg, u32 val)
-{
-	WARN_ON(!mutex_is_locked(&priv->reg_lock));
-
-	return priv->reg_ops->write(priv->reg_ctx, reg, val);
-}
-
-static int
-yt921x_reg_wait(struct yt921x_priv *priv, u32 reg, u32 mask, u32 *valp)
-{
-	u32 val;
-	int res;
-	int ret;
-
-	ret = read_poll_timeout(yt921x_reg_read, res,
-				res || (val & mask) == *valp,
-				YT921X_POLL_SLEEP_US, YT921X_POLL_TIMEOUT_US,
-				false, priv, reg, &val);
-	if (ret)
-		return ret;
-	if (res)
-		return res;
-
-	*valp = val;
-	return 0;
-}
-
-static int
-yt921x_reg_update_bits(struct yt921x_priv *priv, u32 reg, u32 mask, u32 val)
-{
-	int res;
-	u32 v;
-	u32 u;
-
-	res = yt921x_reg_read(priv, reg, &v);
-	if (res)
-		return res;
-
-	u = v;
-	u &= ~mask;
-	u |= val;
-	if (u == v)
-		return 0;
-
-	return yt921x_reg_write(priv, reg, u);
-}
-
-static int yt921x_reg_set_bits(struct yt921x_priv *priv, u32 reg, u32 mask)
-{
-	return yt921x_reg_update_bits(priv, reg, 0, mask);
-}
-
-static int yt921x_reg_clear_bits(struct yt921x_priv *priv, u32 reg, u32 mask)
-{
-	return yt921x_reg_update_bits(priv, reg, mask, 0);
-}
-
-static int
-yt921x_reg_toggle_bits(struct yt921x_priv *priv, u32 reg, u32 mask, bool set)
-{
-	return yt921x_reg_update_bits(priv, reg, mask, !set ? 0 : mask);
-}
-
-/* Some multi-word registers, like VLANn_CTRL, should be treated as a single
- * long register. More specifically, writes to parts of its words won't become
- * visible, until the last word is written.
- *
- * Here we require full read and write operations over these registers to
- * eliminate potential issues, although partial reads/writes are also possible.
- */
-
-static void update_ctrls_unaligned(u32 *lo, u32 *hi, u64 mask, u64 val)
-{
-	*lo &= ~lower_32_bits(mask);
-	*hi &= ~upper_32_bits(mask);
-	*lo |= lower_32_bits(val);
-	*hi |= upper_32_bits(val);
-}
-
-static int
-yt921x_regs_read(struct yt921x_priv *priv, u32 reg, u32 *vals,
-		 unsigned int num_regs)
-{
-	int res;
-
-	for (unsigned int i = 0; i < num_regs; i++) {
-		res = yt921x_reg_read(priv, reg + 4 * i, &vals[i]);
-		if (res)
-			return res;
-	}
-
-	return 0;
-}
-
-static int
-yt921x_regs_write(struct yt921x_priv *priv, u32 reg, const u32 *vals,
-		  unsigned int num_regs)
-{
-	int res;
-
-	for (unsigned int i = 0; i < num_regs; i++) {
-		res = yt921x_reg_write(priv, reg + 4 * i, vals[i]);
-		if (res)
-			return res;
-	}
-
-	return 0;
-}
-
-static int
-yt921x_regs_update_bits(struct yt921x_priv *priv, u32 reg, const u32 *masks,
-			const u32 *vals, unsigned int num_regs)
-{
-	bool changed = false;
-	u32 vs[4];
-	int res;
-
-	BUILD_BUG_ON(num_regs > ARRAY_SIZE(vs));
-
-	res = yt921x_regs_read(priv, reg, vs, num_regs);
-	if (res)
-		return res;
-
-	for (unsigned int i = 0; i < num_regs; i++) {
-		u32 u = vs[i];
-
-		u &= ~masks[i];
-		u |= vals[i];
-		if (u != vs[i])
-			changed = true;
-
-		vs[i] = u;
-	}
-
-	if (!changed)
-		return 0;
-
-	return yt921x_regs_write(priv, reg, vs, num_regs);
-}
-
-static int
-yt921x_regs_clear_bits(struct yt921x_priv *priv, u32 reg, const u32 *masks,
-		       unsigned int num_regs)
-{
-	bool changed = false;
-	u32 vs[4];
-	int res;
-
-	BUILD_BUG_ON(num_regs > ARRAY_SIZE(vs));
-
-	res = yt921x_regs_read(priv, reg, vs, num_regs);
-	if (res)
-		return res;
-
-	for (unsigned int i = 0; i < num_regs; i++) {
-		u32 u = vs[i];
-
-		u &= ~masks[i];
-		if (u != vs[i])
-			changed = true;
-
-		vs[i] = u;
-	}
-
-	if (!changed)
-		return 0;
-
-	return yt921x_regs_write(priv, reg, vs, num_regs);
-}
-
-static int
-yt921x_reg64_write(struct yt921x_priv *priv, u32 reg, const u32 *vals)
-{
-	return yt921x_regs_write(priv, reg, vals, 2);
-}
-
-static int
-yt921x_reg64_update_bits(struct yt921x_priv *priv, u32 reg, const u32 *masks,
-			 const u32 *vals)
-{
-	return yt921x_regs_update_bits(priv, reg, masks, vals, 2);
-}
-
-static int
-yt921x_reg64_clear_bits(struct yt921x_priv *priv, u32 reg, const u32 *masks)
-{
-	return yt921x_regs_clear_bits(priv, reg, masks, 2);
-}
-
-static int
-yt921x_reg96_write(struct yt921x_priv *priv, u32 reg, const u32 *vals)
-{
-	return yt921x_regs_write(priv, reg, vals, 3);
-}
-
 static int yt921x_reg_mdio_read(void *context, u32 reg, u32 *valp)
 {
 	struct yt921x_reg_mdio *mdio = context;

@@ -0,0 +1,157 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Copyright (c) 2026 David Yang
+ */
+
+#include <linux/iopoll.h>
+
+#include "chip.h"
+#include "smi.h"
+
+#define YT921X_POLL_SLEEP_US	10000
+#define YT921X_POLL_TIMEOUT_US	100000
+
+int yt921x_reg_read(struct yt921x_priv *priv, u32 reg, u32 *valp)
+{
+	lockdep_assert_held_once(&priv->reg_lock);
+
+	return priv->reg_ops->read(priv->reg_ctx, reg, valp);
+}
+
+int yt921x_reg_write(struct yt921x_priv *priv, u32 reg, u32 val)
+{
+	lockdep_assert_held_once(&priv->reg_lock);
+
+	return priv->reg_ops->write(priv->reg_ctx, reg, val);
+}
+
+int yt921x_reg_wait(struct yt921x_priv *priv, u32 reg, u32 mask, u32 *valp)
+{
+	u32 val;
+	int res;
+	int ret;
+
+	ret = read_poll_timeout(yt921x_reg_read, res,
+				res || (val & mask) == *valp,
+				YT921X_POLL_SLEEP_US, YT921X_POLL_TIMEOUT_US,
+				false, priv, reg, &val);
+	if (ret)
+		return ret;
+	if (res)
+		return res;
+
+	*valp = val;
+	return 0;
+}
+
+int yt921x_reg_update_bits(struct yt921x_priv *priv, u32 reg, u32 mask, u32 val)
+{
+	int res;
+	u32 v;
+	u32 u;
+
+	res = yt921x_reg_read(priv, reg, &v);
+	if (res)
+		return res;
+
+	u = v;
+	u &= ~mask;
+	u |= val;
+	if (u == v)
+		return 0;
+
+	return yt921x_reg_write(priv, reg, u);
+}
+
+int
+yt921x_regs_read(struct yt921x_priv *priv, u32 reg, u32 *vals,
+		 unsigned int num_regs)
+{
+	int res;
+
+	for (unsigned int i = 0; i < num_regs; i++) {
+		res = yt921x_reg_read(priv, reg + 4 * i, &vals[i]);
+		if (res)
+			return res;
+	}
+
+	return 0;
+}
+
+int
+yt921x_regs_write(struct yt921x_priv *priv, u32 reg, const u32 *vals,
+		  unsigned int num_regs)
+{
+	int res;
+
+	for (unsigned int i = 0; i < num_regs; i++) {
+		res = yt921x_reg_write(priv, reg + 4 * i, vals[i]);
+		if (res)
+			return res;
+	}
+
+	return 0;
+}
+
+int
+yt921x_regs_update_bits(struct yt921x_priv *priv, u32 reg, const u32 *masks,
+			const u32 *vals, unsigned int num_regs)
+{
+	bool changed = false;
+	u32 vs[4];
+	int res;
+
+	if (WARN_ON_ONCE(num_regs > ARRAY_SIZE(vs)))
+		return -EINVAL;
+
+	res = yt921x_regs_read(priv, reg, vs, num_regs);
+	if (res)
+		return res;
+
+	for (unsigned int i = 0; i < num_regs; i++) {
+		u32 u = vs[i];
+
+		u &= ~masks[i];
+		u |= vals[i];
+		if (u != vs[i])
+			changed = true;
+
+		vs[i] = u;
+	}
+
+	if (!changed)
+		return 0;
+
+	return yt921x_regs_write(priv, reg, vs, num_regs);
+}
+
+int
+yt921x_regs_clear_bits(struct yt921x_priv *priv, u32 reg, const u32 *masks,
+		       unsigned int num_regs)
+{
+	bool changed = false;
+	u32 vs[4];
+	int res;
+
+	if (WARN_ON_ONCE(num_regs > ARRAY_SIZE(vs)))
+		return -EINVAL;
+
+	res = yt921x_regs_read(priv, reg, vs, num_regs);
+	if (res)
+		return res;
+
+	for (unsigned int i = 0; i < num_regs; i++) {
+		u32 u = vs[i];
+
+		u &= ~masks[i];
+		if (u != vs[i])
+			changed = true;
+
+		vs[i] = u;
+	}
+
+	if (!changed)
+		return 0;
+
+	return yt921x_regs_write(priv, reg, vs, num_regs);
+}

@@ -0,0 +1,88 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/*
+ * Copyright (c) 2026 David Yang
+ */
+
+#ifndef _YT_SMI_H
+#define _YT_SMI_H
+
+#include <linux/types.h>
+#include <linux/wordpart.h>
+
+struct yt921x_priv;
+
+int yt921x_reg_read(struct yt921x_priv *priv, u32 reg, u32 *valp);
+int yt921x_reg_write(struct yt921x_priv *priv, u32 reg, u32 val);
+int yt921x_reg_wait(struct yt921x_priv *priv, u32 reg, u32 mask, u32 *valp);
+int yt921x_reg_update_bits(struct yt921x_priv *priv, u32 reg, u32 mask,
+			   u32 val);
+
+static inline int
+yt921x_reg_set_bits(struct yt921x_priv *priv, u32 reg, u32 mask)
+{
+	return yt921x_reg_update_bits(priv, reg, 0, mask);
+}
+
+static inline int
+yt921x_reg_clear_bits(struct yt921x_priv *priv, u32 reg, u32 mask)
+{
+	return yt921x_reg_update_bits(priv, reg, mask, 0);
+}
+
+static inline int
+yt921x_reg_toggle_bits(struct yt921x_priv *priv, u32 reg, u32 mask, bool set)
+{
+	return yt921x_reg_update_bits(priv, reg, mask, !set ? 0 : mask);
+}
+
+/* Some multi-word registers, like VLANn_CTRL, should be treated as a single
+ * long register. More specifically, writes to parts of its words won't become
+ * visible, until the last word is written.
+ *
+ * Here we require full read and write operations over these registers to
+ * eliminate potential issues, although partial reads/writes are also possible.
+ */
+
+static inline void update_ctrls_unaligned(u32 *lo, u32 *hi, u64 mask, u64 val)
+{
+	*lo &= ~lower_32_bits(mask);
+	*hi &= ~upper_32_bits(mask);
+	*lo |= lower_32_bits(val);
+	*hi |= upper_32_bits(val);
+}
+
+int yt921x_regs_read(struct yt921x_priv *priv, u32 reg, u32 *vals,
+		     unsigned int num_regs);
+int yt921x_regs_write(struct yt921x_priv *priv, u32 reg, const u32 *vals,
+		      unsigned int num_regs);
+int yt921x_regs_update_bits(struct yt921x_priv *priv, u32 reg, const u32 *masks,
+			    const u32 *vals, unsigned int num_regs);
+int yt921x_regs_clear_bits(struct yt921x_priv *priv, u32 reg, const u32 *masks,
+			   unsigned int num_regs);
+
+static inline int
+yt921x_reg64_write(struct yt921x_priv *priv, u32 reg, const u32 *vals)
+{
+	return yt921x_regs_write(priv, reg, vals, 2);
+}
+
+static inline int
+yt921x_reg64_update_bits(struct yt921x_priv *priv, u32 reg, const u32 *masks,
+			 const u32 *vals)
+{
+	return yt921x_regs_update_bits(priv, reg, masks, vals, 2);
+}
+
+static inline int
+yt921x_reg64_clear_bits(struct yt921x_priv *priv, u32 reg, const u32 *masks)
+{
+	return yt921x_regs_clear_bits(priv, reg, masks, 2);
+}
+
+static inline int
+yt921x_reg96_write(struct yt921x_priv *priv, u32 reg, const u32 *vals)
+{
+	return yt921x_regs_write(priv, reg, vals, 3);
+}
+
+#endif