regulator: add support for SGM3804 Dual Output driver

Neil Armstrong <neil.armstrong@linaro.org> says:

Add support for the SG Micro SGM3804 Single Inductor Dual Output
Buck/Boost Converter used to power LCD panels a provide positive
and negative power rails with configurable voltage and active
discharge function for each output.

The SGM3804 is powered by the enable GPIO pins inputs and only
supports I2C write messages.
In order to add flexibility and simplify the driver, the
regmap cache is enabled and populated with default values
since we can't write registers when the 2 GPIOs are down.

This regulator is used to provide vsn and vsn power to the
Ayaneo Pocket S2 dual-DSI LCD panel.

Link: https://patch.msgid.link/20260522-topic-sm8650-ayaneo-pocket-s2-sgm3804-v5-0-bd6b1c300ecc@linaro.org

3 files changed, 51 insertions, 21 deletions

diff --git a/drivers/net/netdevsim/netdev.c b/drivers/net/netdevsim/netdev.c
index a05af192caf3..a750768912b5 100644
--- a/drivers/net/netdevsim/netdev.c
+++ b/drivers/net/netdevsim/netdev.c
@@ -1182,7 +1182,8 @@ void nsim_destroy(struct netdevsim *ns)
 		unregister_netdevice_notifier_dev_net(ns->netdev, &ns->nb,
 						      &ns->nn);
 
-	nsim_psp_uninit(ns);
+	if (nsim_dev_port_is_pf(ns->nsim_dev_port))
+		nsim_psp_uninit(ns);
 
 	rtnl_lock();
 	peer = rtnl_dereference(ns->peer);
diff --git a/drivers/net/netdevsim/netdevsim.h b/drivers/net/netdevsim/netdevsim.h
index 7e129dddbbe7..d909c4160ea1 100644
--- a/drivers/net/netdevsim/netdevsim.h
+++ b/drivers/net/netdevsim/netdevsim.h
@@ -120,7 +120,9 @@ struct netdevsim {
 		u64_stats_t tx_packets;
 		u64_stats_t tx_bytes;
 		struct u64_stats_sync syncp;
-		struct psp_dev *dev;
+		struct psp_dev __rcu *dev;
+		struct dentry *rereg;
+		struct mutex rereg_lock;
 		u32 spi;
 		u32 assoc_cnt;
 	} psp;
diff --git a/drivers/net/netdevsim/psp.c b/drivers/net/netdevsim/psp.c
index 0b4d717253b0..6936ecb8173e 100644
--- a/drivers/net/netdevsim/psp.c
+++ b/drivers/net/netdevsim/psp.c
@@ -19,6 +19,7 @@ nsim_do_psp(struct sk_buff *skb, struct netdevsim *ns,
 	    struct netdevsim *peer_ns, struct skb_ext **psp_ext)
 {
 	enum skb_drop_reason rc = 0;
+	struct psp_dev *peer_psd;
 	struct psp_assoc *pas;
 	struct net *net;
 	void **ptr;
@@ -48,7 +49,8 @@ nsim_do_psp(struct sk_buff *skb, struct netdevsim *ns,
 	}
 
 	/* Now pretend we just received this frame */
-	if (peer_ns->psp.dev->config.versions & (1 << pas->version)) {
+	peer_psd = rcu_dereference(peer_ns->psp.dev);
+	if (peer_psd && peer_psd->config.versions & (1 << pas->version)) {
 		bool strip_icv = false;
 		u8 generation;
 
@@ -61,8 +63,7 @@ nsim_do_psp(struct sk_buff *skb, struct netdevsim *ns,
 
 		skb_ext_reset(skb);
 		skb->mac_len = ETH_HLEN;
-		if (psp_dev_rcv(skb, peer_ns->psp.dev->id, generation,
-				strip_icv)) {
+		if (psp_dev_rcv(skb, peer_psd->id, generation, strip_icv)) {
 			rc = SKB_DROP_REASON_PSP_OUTPUT;
 			goto out_unlock;
 		}
@@ -209,26 +210,50 @@ static struct psp_dev_caps nsim_psp_caps = {
 	.assoc_drv_spc = sizeof(void *),
 };
 
-void nsim_psp_uninit(struct netdevsim *ns)
+static void __nsim_psp_uninit(struct netdevsim *ns, bool teardown)
 {
-	if (!IS_ERR(ns->psp.dev))
-		psp_dev_unregister(ns->psp.dev);
+	struct psp_dev *psd;
+
+	psd = rcu_dereference_protected(ns->psp.dev,
+					teardown ||
+					lockdep_is_held(&ns->psp.rereg_lock));
+	if (psd) {
+		rcu_assign_pointer(ns->psp.dev, NULL);
+		synchronize_rcu();
+		psp_dev_unregister(psd);
+	}
 	WARN_ON(ns->psp.assoc_cnt);
 }
 
+void nsim_psp_uninit(struct netdevsim *ns)
+{
+	debugfs_remove(ns->psp.rereg);
+	mutex_destroy(&ns->psp.rereg_lock);
+	__nsim_psp_uninit(ns, true);
+}
+
 static ssize_t
 nsim_psp_rereg_write(struct file *file, const char __user *data, size_t count,
 		     loff_t *ppos)
 {
 	struct netdevsim *ns = file->private_data;
-	int err;
+	struct psp_dev *psd;
+	ssize_t ret;
+
+	mutex_lock(&ns->psp.rereg_lock);
+	__nsim_psp_uninit(ns, false);
 
-	nsim_psp_uninit(ns);
+	psd = psp_dev_create(ns->netdev, &nsim_psp_ops, &nsim_psp_caps, ns);
+	if (IS_ERR(psd)) {
+		ret = PTR_ERR(psd);
+		goto out;
+	}
 
-	ns->psp.dev = psp_dev_create(ns->netdev, &nsim_psp_ops,
-				     &nsim_psp_caps, ns);
-	err = PTR_ERR_OR_ZERO(ns->psp.dev);
-	return err ?: count;
+	rcu_assign_pointer(ns->psp.dev, psd);
+	ret = count;
+out:
+	mutex_unlock(&ns->psp.rereg_lock);
+	return ret;
 }
 
 static const struct file_operations nsim_psp_rereg_fops = {
@@ -241,14 +266,16 @@ static const struct file_operations nsim_psp_rereg_fops = {
 int nsim_psp_init(struct netdevsim *ns)
 {
 	struct dentry *ddir = ns->nsim_dev_port->ddir;
-	int err;
+	struct psp_dev *psd;
+
+	psd = psp_dev_create(ns->netdev, &nsim_psp_ops, &nsim_psp_caps, ns);
+	if (IS_ERR(psd))
+		return PTR_ERR(psd);
 
-	ns->psp.dev = psp_dev_create(ns->netdev, &nsim_psp_ops,
-				     &nsim_psp_caps, ns);
-	err = PTR_ERR_OR_ZERO(ns->psp.dev);
-	if (err)
-		return err;
+	rcu_assign_pointer(ns->psp.dev, psd);
 
-	debugfs_create_file("psp_rereg", 0200, ddir, ns, &nsim_psp_rereg_fops);
+	mutex_init(&ns->psp.rereg_lock);
+	ns->psp.rereg = debugfs_create_file("psp_rereg", 0200, ddir, ns,
+					    &nsim_psp_rereg_fops);
 	return 0;
 }