Merge branch 'net-sfp-extend-smbus-support'

Jonas Jelonek says:

====================
net: sfp: extend SMBus support

Today, the SFP driver only drives I2C adapters that advertise full
I2C_FUNC_I2C, or SMBus-only adapters via single-byte transfers (with
hwmon disabled). Several SoCs ship I2C/SMBus-only controllers that
support more than just byte access -- e.g. word and I2C block -- and
have SFP cages wired to them. Today, those adapters either work
poorly or not at all.

This series teaches the SFP driver to use the larger SMBus access
modes when the adapter advertises them, and along the way starts
honoring i2c_adapter quirks on read/write length so adapters that
cap below the SFP block size are handled correctly. Patch 1 is a
small prep doing only the quirks handling; patch 2 extends the
SMBus path itself.

Capability matrix supported by patch 2:
  - BYTE only:                   single-byte access (unchanged).
  - BYTE + WORD:                 word for >=2-byte chunks, byte tail.
  - I2C_BLOCK present:           block as the universal transport.
  - WORD only (no BYTE/BLOCK):   accepted with WARN_ONCE; works for
                                 even-length transfers, odd-length
                                 transfers will error at xfer time.

Adapters with asymmetric R/W capabilities (e.g. only READ_I2C_BLOCK
without WRITE_I2C_BLOCK) remain functionally correct but use the
worse-supported direction's max for both directions, since
i2c_max_block_size is a single field. No mainline I2C driver was
seen advertising such asymmetry; per-direction sizes can be added
later if needed.
====================

Link: https://patch.msgid.link/20260614133418.2068201-1-jelonek.jonas@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

1 files changed, 120 insertions, 29 deletions

diff --git a/drivers/net/phy/sfp.c b/drivers/net/phy/sfp.c
index caeda3291b30..03bfd8640db9 100644
--- a/drivers/net/phy/sfp.c
+++ b/drivers/net/phy/sfp.c
@@ -14,6 +14,7 @@
 #include <linux/platform_device.h>
 #include <linux/rtnetlink.h>
 #include <linux/slab.h>
+#include <linux/unaligned.h>
 #include <linux/workqueue.h>
 
 #include "sfp.h"
@@ -776,50 +777,113 @@ static int sfp_i2c_write(struct sfp *sfp, bool a2, u8 dev_addr, void *buf,
 	return ret == ARRAY_SIZE(msgs) ? len : 0;
 }
 
-static int sfp_smbus_byte_read(struct sfp *sfp, bool a2, u8 dev_addr,
-			       void *buf, size_t len)
+static int sfp_smbus_read(struct sfp *sfp, bool a2, u8 dev_addr, void *buf,
+			  size_t len)
 {
-	union i2c_smbus_data smbus_data;
+	union i2c_smbus_data smbus_data = {0};
 	u8 bus_addr = a2 ? 0x51 : 0x50;
+	size_t this_len, transferred;
+	u32 functionality;
 	u8 *data = buf;
 	int ret;
 
-	while (len) {
-		ret = i2c_smbus_xfer(sfp->i2c, bus_addr, 0,
-				     I2C_SMBUS_READ, dev_addr,
-				     I2C_SMBUS_BYTE_DATA, &smbus_data);
-		if (ret < 0)
-			return ret;
+	functionality = i2c_get_functionality(sfp->i2c);
 
-		*data = smbus_data.byte;
+	while (len) {
+		this_len = min(len, sfp->i2c_block_size);
+
+		if (functionality & I2C_FUNC_SMBUS_READ_I2C_BLOCK) {
+			smbus_data.block[0] = this_len;
+			ret = i2c_smbus_xfer(sfp->i2c, bus_addr, 0,
+					     I2C_SMBUS_READ, dev_addr,
+					     I2C_SMBUS_I2C_BLOCK_DATA, &smbus_data);
+			if (ret < 0)
+				return ret;
+
+			transferred = min_t(size_t, smbus_data.block[0], this_len);
+			if (!transferred)
+				return -EIO;
+
+			memcpy(data, &smbus_data.block[1], transferred);
+		} else if (this_len >= 2 &&
+			   (functionality & I2C_FUNC_SMBUS_READ_WORD_DATA)) {
+			ret = i2c_smbus_xfer(sfp->i2c, bus_addr, 0,
+					     I2C_SMBUS_READ, dev_addr,
+					     I2C_SMBUS_WORD_DATA, &smbus_data);
+			if (ret < 0)
+				return ret;
+
+			put_unaligned_le16(smbus_data.word, data);
+			transferred = 2;
+		} else {
+			ret = i2c_smbus_xfer(sfp->i2c, bus_addr, 0,
+					     I2C_SMBUS_READ, dev_addr,
+					     I2C_SMBUS_BYTE_DATA, &smbus_data);
+			if (ret < 0)
+				return ret;
+
+			*data = smbus_data.byte;
+			transferred = 1;
+		}
 
-		len--;
-		data++;
-		dev_addr++;
+		data += transferred;
+		len -= transferred;
+		dev_addr += transferred;
 	}
 
 	return data - (u8 *)buf;
 }
 
-static int sfp_smbus_byte_write(struct sfp *sfp, bool a2, u8 dev_addr,
-				void *buf, size_t len)
+static int sfp_smbus_write(struct sfp *sfp, bool a2, u8 dev_addr, void *buf,
+			   size_t len)
 {
 	union i2c_smbus_data smbus_data;
 	u8 bus_addr = a2 ? 0x51 : 0x50;
+	size_t this_len, transferred;
+	u32 functionality;
 	u8 *data = buf;
 	int ret;
 
+	functionality = i2c_get_functionality(sfp->i2c);
+
 	while (len) {
-		smbus_data.byte = *data;
-		ret = i2c_smbus_xfer(sfp->i2c, bus_addr, 0,
-				     I2C_SMBUS_WRITE, dev_addr,
-				     I2C_SMBUS_BYTE_DATA, &smbus_data);
-		if (ret)
-			return ret;
+		this_len = min(len, sfp->i2c_block_size);
+
+		if (functionality & I2C_FUNC_SMBUS_WRITE_I2C_BLOCK) {
+			smbus_data.block[0] = this_len;
+			memcpy(&smbus_data.block[1], data, this_len);
+
+			ret = i2c_smbus_xfer(sfp->i2c, bus_addr, 0,
+					     I2C_SMBUS_WRITE, dev_addr,
+					     I2C_SMBUS_I2C_BLOCK_DATA, &smbus_data);
+			if (ret < 0)
+				return ret;
+
+			transferred = this_len;
+		} else if (this_len >= 2 &&
+			   (functionality & I2C_FUNC_SMBUS_WRITE_WORD_DATA)) {
+			smbus_data.word = get_unaligned_le16(data);
+			ret = i2c_smbus_xfer(sfp->i2c, bus_addr, 0,
+					     I2C_SMBUS_WRITE, dev_addr,
+					     I2C_SMBUS_WORD_DATA, &smbus_data);
+			if (ret < 0)
+				return ret;
+
+			transferred = 2;
+		} else {
+			smbus_data.byte = *data;
+			ret = i2c_smbus_xfer(sfp->i2c, bus_addr, 0,
+					     I2C_SMBUS_WRITE, dev_addr,
+					     I2C_SMBUS_BYTE_DATA, &smbus_data);
+			if (ret < 0)
+				return ret;
+
+			transferred = 1;
+		}
 
-		len--;
-		data++;
-		dev_addr++;
+		data += transferred;
+		len -= transferred;
+		dev_addr += transferred;
 	}
 
 	return data - (u8 *)buf;
@@ -827,21 +891,48 @@ static int sfp_smbus_byte_write(struct sfp *sfp, bool a2, u8 dev_addr,
 
 static int sfp_i2c_configure(struct sfp *sfp, struct i2c_adapter *i2c)
 {
+	size_t max_block_size;
+
 	sfp->i2c = i2c;
 
 	if (i2c_check_functionality(i2c, I2C_FUNC_I2C)) {
 		sfp->read = sfp_i2c_read;
 		sfp->write = sfp_i2c_write;
-		sfp->i2c_max_block_size = SFP_EEPROM_BLOCK_SIZE;
-	} else if (i2c_check_functionality(i2c, I2C_FUNC_SMBUS_BYTE_DATA)) {
-		sfp->read = sfp_smbus_byte_read;
-		sfp->write = sfp_smbus_byte_write;
-		sfp->i2c_max_block_size = 1;
+		max_block_size = SFP_EEPROM_BLOCK_SIZE;
+	} else if (i2c_check_functionality(i2c, I2C_FUNC_SMBUS_BYTE_DATA) ||
+		   i2c_check_functionality(i2c, I2C_FUNC_SMBUS_I2C_BLOCK)) {
+		/* Either protocol alone covers any length: I2C-block carries
+		 * 1..32 bytes per xfer, byte iterates one byte at a time.
+		 */
+		sfp->read = sfp_smbus_read;
+		sfp->write = sfp_smbus_write;
+
+		if (i2c_check_functionality(i2c, I2C_FUNC_SMBUS_I2C_BLOCK))
+			max_block_size = SFP_EEPROM_BLOCK_SIZE;
+		else if (i2c_check_functionality(i2c, I2C_FUNC_SMBUS_WORD_DATA))
+			max_block_size = 2;
+		else
+			max_block_size = 1;
+	} else if (WARN_ONCE(i2c_check_functionality(i2c, I2C_FUNC_SMBUS_WORD_DATA),
+			     "SMBus word-only adapter; odd-length transfers will fail\n")) {
+		/* Word-only: even-length xfers work; odd-length xfers fall
+		 * to BYTE, which the adapter does not advertise and will
+		 * likely fail.
+		 */
+		sfp->read = sfp_smbus_read;
+		sfp->write = sfp_smbus_write;
+		max_block_size = 2;
 	} else {
 		sfp->i2c = NULL;
 		return -EINVAL;
 	}
 
+	if (i2c->quirks && i2c->quirks->max_read_len)
+		max_block_size = min(max_block_size, i2c->quirks->max_read_len);
+	if (i2c->quirks && i2c->quirks->max_write_len)
+		max_block_size = min(max_block_size, i2c->quirks->max_write_len);
+
+	sfp->i2c_max_block_size = max_block_size;
 	sfp->i2c_block_size = sfp->i2c_max_block_size;
 	return 0;
 }