[PATCH v2 2/3] nfc: st-nci: add raw NCI path for ST21NFCD

[Kristian Brox <isyourbrainfoss@proton.me>]

ST21NFCD does not use NDLC. When the compatible is st,st21nfcd,
talk raw NCI:

- do not add or strip an NDLC PCB
- do not run the T1/T2 ACK timers
- I2C reads are a 3-byte NCI header plus payload
- skip proprietary SET_NFC_MODE and HCI SE discovery

Optionally enable clocks (SYS_CLK) and vdd-io (VPS_IO) when the
DT describes them. Existing st21nfcb / st21nfcc boards keep the
NDLC path and do not need those properties.

Tested on Fairphone 5: adapter powers up and reads an NTAG 215.

Signed-off-by: Kristian Brox <isyourbrainfoss@proton.me>
---
diff --git a/drivers/nfc/st-nci/core.c b/drivers/nfc/st-nci/core.c
index a367136..2356f16 100644
--- a/drivers/nfc/st-nci/core.c
+++ b/drivers/nfc/st-nci/core.c
@@ -18,8 +18,13 @@
 
 static int st_nci_init(struct nci_dev *ndev)
 {
+	struct st_nci_info *info = nci_get_drvdata(ndev);
 	struct nci_mode_set_cmd cmd;
 
+	/* ST21NFCD has no NDLC proprietary SET_NFC_MODE */
+	if (info->ndlc->raw_nci)
+		return 0;
+
 	cmd.cmd_type = ST_NCI_SET_NFC_MODE;
 	cmd.mode = 1;
 
diff --git a/drivers/nfc/st-nci/i2c.c b/drivers/nfc/st-nci/i2c.c
index 416770a..cfddb7f 100644
--- a/drivers/nfc/st-nci/i2c.c
+++ b/drivers/nfc/st-nci/i2c.c
@@ -10,10 +10,13 @@
 #include <linux/i2c.h>
 #include <linux/gpio/consumer.h>
 #include <linux/acpi.h>
+#include <linux/clk.h>
 #include <linux/interrupt.h>
 #include <linux/delay.h>
 #include <linux/nfc.h>
 #include <linux/of.h>
+#include <linux/property.h>
+#include <linux/regulator/consumer.h>
 
 #include "st-nci.h"
 
@@ -22,10 +25,17 @@
 /* ndlc header */
 #define ST_NCI_FRAME_HEADROOM 1
 #define ST_NCI_FRAME_TAILROOM 0
+#define ST_NCI_RAW_FRAME_HEADROOM 0
 
 #define ST_NCI_I2C_MIN_SIZE 4   /* PCB(1) + NCI Packet header(3) */
+#define ST_NCI_NCI_HDR_SIZE 3   /* raw NCI: MT/PBF/GID + OID + len */
 #define ST_NCI_I2C_MAX_SIZE 250 /* req 4.2.1 */
 
+enum st_nci_i2c_proto {
+	ST_NCI_I2C_PROTO_NDLC = 0,
+	ST_NCI_I2C_PROTO_RAW_NCI,
+};
+
 #define ST_NCI_DRIVER_NAME "st_nci"
 #define ST_NCI_I2C_DRIVER_NAME "st_nci_i2c"
 
@@ -34,6 +44,7 @@ struct st_nci_i2c_phy {
 	struct llt_ndlc *ndlc;
 
 	bool irq_active;
+	bool raw_nci;
 
 	struct gpio_desc *gpiod_reset;
 
@@ -111,6 +122,42 @@ static int st_nci_i2c_read(struct st_nci_i2c_phy *phy,
 	u8 buf[ST_NCI_I2C_MAX_SIZE];
 	struct i2c_client *client = phy->i2c_dev;
 
+	if (phy->raw_nci) {
+		r = i2c_master_recv(client, buf, ST_NCI_NCI_HDR_SIZE);
+		if (r < 0) {
+			usleep_range(1000, 4000);
+			r = i2c_master_recv(client, buf, ST_NCI_NCI_HDR_SIZE);
+		}
+		if (r != ST_NCI_NCI_HDR_SIZE)
+			return -EREMOTEIO;
+
+		len = buf[2];
+		if (len > ST_NCI_I2C_MAX_SIZE) {
+			nfc_err(&client->dev, "invalid frame len\n");
+			return -EBADMSG;
+		}
+
+		*skb = alloc_skb(ST_NCI_NCI_HDR_SIZE + len, GFP_KERNEL);
+		if (!*skb)
+			return -ENOMEM;
+
+		skb_put(*skb, ST_NCI_NCI_HDR_SIZE);
+		memcpy((*skb)->data, buf, ST_NCI_NCI_HDR_SIZE);
+
+		if (!len)
+			return 0;
+
+		r = i2c_master_recv(client, buf, len);
+		if (r != len) {
+			kfree_skb(*skb);
+			return -EREMOTEIO;
+		}
+
+		skb_put(*skb, len);
+		memcpy((*skb)->data + ST_NCI_NCI_HDR_SIZE, buf, len);
+		return 0;
+	}
+
 	r = i2c_master_recv(client, buf, ST_NCI_I2C_MIN_SIZE);
 	if (r < 0) {  /* Retry, chip was in standby */
 		usleep_range(1000, 4000);
@@ -211,6 +258,8 @@ static int st_nci_i2c_probe(struct i2c_client *client)
 		return -ENOMEM;
 
 	phy->i2c_dev = client;
+	phy->raw_nci = (uintptr_t)device_get_match_data(dev) ==
+			ST_NCI_I2C_PROTO_RAW_NCI;
 
 	i2c_set_clientdata(client, phy);
 
@@ -225,19 +274,31 @@ static int st_nci_i2c_probe(struct i2c_client *client)
 		return -ENODEV;
 	}
 
+	r = devm_regulator_get_enable_optional(dev, "vdd-io");
+	if (r && r != -ENODEV)
+		return dev_err_probe(dev, r, "failed to enable vdd-io\n");
+
+	r = PTR_ERR_OR_ZERO(devm_clk_get_optional_enabled(dev, NULL));
+	if (r)
+		return dev_err_probe(dev, r, "failed to enable clock\n");
+
 	phy->se_status.is_ese_present =
 				device_property_read_bool(dev, "ese-present");
 	phy->se_status.is_uicc_present =
 				device_property_read_bool(dev, "uicc-present");
 
 	r = ndlc_probe(phy, &i2c_phy_ops, &client->dev,
-			ST_NCI_FRAME_HEADROOM, ST_NCI_FRAME_TAILROOM,
+			phy->raw_nci ? ST_NCI_RAW_FRAME_HEADROOM :
+				       ST_NCI_FRAME_HEADROOM,
+			ST_NCI_FRAME_TAILROOM,
 			&phy->ndlc, &phy->se_status);
 	if (r < 0) {
 		nfc_err(&client->dev, "Unable to register ndlc layer\n");
 		return r;
 	}
 
+	phy->ndlc->raw_nci = phy->raw_nci;
+
 	phy->irq_active = true;
 	r = devm_request_threaded_irq(&client->dev, client->irq, NULL,
 				st_nci_irq_thread_fn,
@@ -273,6 +334,8 @@ static const struct of_device_id of_st_nci_i2c_match[] __maybe_unused = {
 	{ .compatible = "st,st21nfcb-i2c", },
 	{ .compatible = "st,st21nfcb_i2c", },
 	{ .compatible = "st,st21nfcc-i2c", },
+	{ .compatible = "st,st21nfcd",
+	  .data = (void *)ST_NCI_I2C_PROTO_RAW_NCI },
 	{}
 };
 MODULE_DEVICE_TABLE(of, of_st_nci_i2c_match);
diff --git a/drivers/nfc/st-nci/ndlc.c b/drivers/nfc/st-nci/ndlc.c
index be48088..b319246 100644
--- a/drivers/nfc/st-nci/ndlc.c
+++ b/drivers/nfc/st-nci/ndlc.c
@@ -62,8 +62,9 @@ void ndlc_close(struct llt_ndlc *ndlc)
 	/* toggle reset pin */
 	ndlc->ops->enable(ndlc->phy_id);
 
-	nci_prop_cmd(ndlc->ndev, ST_NCI_CORE_PROP,
-		     sizeof(struct nci_mode_set_cmd), (__u8 *)&cmd);
+	if (!ndlc->raw_nci)
+		nci_prop_cmd(ndlc->ndev, ST_NCI_CORE_PROP,
+			     sizeof(struct nci_mode_set_cmd), (__u8 *)&cmd);
 
 	ndlc->powered = 0;
 	ndlc->ops->disable(ndlc->phy_id);
@@ -72,11 +73,13 @@ EXPORT_SYMBOL(ndlc_close);
 
 int ndlc_send(struct llt_ndlc *ndlc, struct sk_buff *skb)
 {
-	/* add ndlc header */
-	u8 pcb = PCB_TYPE_DATAFRAME | PCB_DATAFRAME_RETRANSMIT_NO |
-		PCB_FRAME_CRC_INFO_NOTPRESENT;
+	if (!ndlc->raw_nci) {
+		/* add ndlc header */
+		u8 pcb = PCB_TYPE_DATAFRAME | PCB_DATAFRAME_RETRANSMIT_NO |
+			PCB_FRAME_CRC_INFO_NOTPRESENT;
 
-	*(u8 *)skb_push(skb, 1) = pcb;
+		*(u8 *)skb_push(skb, 1) = pcb;
+	}
 	skb_queue_tail(&ndlc->send_q, skb);
 
 	schedule_work(&ndlc->sm_work);
@@ -103,6 +106,10 @@ static void llt_ndlc_send_queue(struct llt_ndlc *ndlc)
 			ndlc->hard_fault = r;
 			break;
 		}
+		if (ndlc->raw_nci) {
+			kfree_skb(skb);
+			continue;
+		}
 		time_sent = jiffies;
 		*(unsigned long *)skb->cb = time_sent;
 
@@ -154,6 +161,10 @@ static void llt_ndlc_rcv_queue(struct llt_ndlc *ndlc)
 		pr_debug("rcvQlen=%d\n", ndlc->rcv_q.qlen);
 
 	while ((skb = skb_dequeue(&ndlc->rcv_q)) != NULL) {
+		if (ndlc->raw_nci) {
+			nci_recv_frame(ndlc->ndev, skb);
+			continue;
+		}
 		pcb = skb->data[0];
 		skb_pull(skb, 1);
 		if ((pcb & PCB_TYPE_MASK) == PCB_TYPE_SUPERVISOR) {
diff --git a/drivers/nfc/st-nci/ndlc.h b/drivers/nfc/st-nci/ndlc.h
index c24ce9b..5c1f8ba 100644
--- a/drivers/nfc/st-nci/ndlc.h
+++ b/drivers/nfc/st-nci/ndlc.h
@@ -39,6 +39,8 @@ struct llt_ndlc {
 	 */
 	int hard_fault;
 	int powered;
+	/* ST21NFCD: raw NCI on the wire, no NDLC PCB / ACK timers */
+	bool raw_nci;
 };
 
 int ndlc_open(struct llt_ndlc *ndlc);
diff --git a/drivers/nfc/st-nci/se.c b/drivers/nfc/st-nci/se.c
index 607ec76..44cc102 100644
--- a/drivers/nfc/st-nci/se.c
+++ b/drivers/nfc/st-nci/se.c
@@ -621,6 +621,9 @@ int st_nci_discover_se(struct nci_dev *ndev)
 	int se_count = 0;
 	struct st_nci_info *info = nci_get_drvdata(ndev);
 
+	if (info->ndlc->raw_nci)
+		return 0;
+
 	r = st_nci_hci_network_init(ndev);
 	if (r != 0)
 		return r;