at24: Support SMBus byte writes to 16-bit devices

PATCH In review Aaron Sierra 3 participants 3 messages Sep 3, 2015 – Nov 3, 2015 2 messages not in the archive

Subsystems (2)

Char and misc drivers I2C subsystem host drivers

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Aaron Sierra

author

2015-09-03 19:53 UTC #2 lore raw

PATCH 2/3 at24: Support SMBus byte writes to 16-bit devices

Introduce at24_smbus_write_byte_data() to allow very slow (e.g. 248 B/s) write access to 16-bit EEPROM devices attached to SMBus controllers like the Intel SCH.

Signed-off-by Nate Case <ncase-AQeFf1F/[email protected]>

Signed-off-by Aaron Sierra <asierra-AQeFf1F/[email protected]>

---
 drivers/misc/eeprom/at24.c | 35 ++++++++++++++++++++++++++++++++---
 1 file changed, 32 insertions(+), 3 deletions(-)

drivers/misc/eeprom/at24.c +32 -3

index 4cf53a0..2ee1301 100644
@@ -134,6 +134,25 @@ MODULE_DEVICE_TABLE(i2c, at24_ids);
 /*-------------------------------------------------------------------------*/
 
 /*
+ * Write a byte to an AT24 device using SMBus cycles.
+ */
+static inline s32 at24_smbus_write_byte_data(struct at24_data *at24,
+	struct i2c_client *client, u16 offset, u8 value)
+{
+	if (!(at24->chip.flags & AT24_FLAG_ADDR16))
+		return i2c_smbus_write_byte_data(client, offset, value);
+
+	/*
+	 * Emulate I2C multi-byte write by using SMBus "write word"
+	 * cycle.  We split up the 16-bit offset among the "command"
+	 * byte and the first data byte.
+	 */
+	return i2c_smbus_write_word_data(client,
+		((offset >> 8) & 0xff),
+		(value << 8) | (offset & 0xff));
+}
+
+/*
  * Write block data to an AT24 device using SMBus cycles.
  */
 static inline s32 at24_smbus_write_i2c_block_data(struct at24_data *at24,

@@ -401,8 +420,8 @@ static ssize_t at24_eeprom_write(struct at24_data *at24, const char *buf,
 						client, offset, count, buf);
 				break;
 			case I2C_SMBUS_BYTE_DATA:
-				status = i2c_smbus_write_byte_data(client,
-						offset, buf[0]);
+				status = at24_smbus_write_byte_data(at24,
+						client, offset, buf[0]);
 				break;
 			}

@@ -590,7 +609,17 @@ static int at24_probe(struct i2c_client *client, const struct i2c_device_id *id)
 		if (i2c_check_functionality(client->adapter,
 				I2C_FUNC_SMBUS_WRITE_I2C_BLOCK)) {
 			use_smbus_write = I2C_SMBUS_I2C_BLOCK_DATA;
-		} else if (i2c_check_functionality(client->adapter,
+		} else if (chip.flags & AT24_FLAG_ADDR16 &&
+		    i2c_check_functionality(client->adapter,
+					I2C_FUNC_SMBUS_WRITE_WORD_DATA)) {
+			/*
+			 * We need SMBUS_WRITE_WORD_DATA to implement
+			 * byte writes for 16-bit address devices.
+			 */
+			use_smbus_write = I2C_SMBUS_BYTE_DATA;
+			chip.page_size = 1;
+		} else if (!(chip.flags & AT24_FLAG_ADDR16) &&
+			i2c_check_functionality(client->adapter,
 				I2C_FUNC_SMBUS_WRITE_BYTE_DATA)) {
 			use_smbus_write = I2C_SMBUS_BYTE_DATA;
 			chip.page_size = 1;

Signature · 1 line

1.9.1

Aaron Sierra

2015-09-21 18:40 UTC #3 lore raw

PATCH v2 2/3 at24: Support SMBus byte writes to 16-bit devices

Introduce at24_smbus_write_byte_data() to allow very slow (e.g. 248 B/s) write access to 16-bit EEPROM devices attached to SMBus controllers like the Intel SCH.

Signed-off-by Nate Case <[email protected]>

Signed-off-by Aaron Sierra <[email protected]>

---
v2 - Unchanged from v1

 drivers/misc/eeprom/at24.c | 35 ++++++++++++++++++++++++++++++++---
 1 file changed, 32 insertions(+), 3 deletions(-)

drivers/misc/eeprom/at24.c +32 -3

index c3d3add..32eca05 100644
@@ -134,6 +134,25 @@ MODULE_DEVICE_TABLE(i2c, at24_ids);
 /*-------------------------------------------------------------------------*/
 
 /*
+ * Write a byte to an AT24 device using SMBus cycles.
+ */
+static inline s32 at24_smbus_write_byte_data(struct at24_data *at24,
+	struct i2c_client *client, u16 offset, u8 value)
+{
+	if (!(at24->chip.flags & AT24_FLAG_ADDR16))
+		return i2c_smbus_write_byte_data(client, offset, value);
+
+	/*
+	 * Emulate I2C multi-byte write by using SMBus "write word"
+	 * cycle.  We split up the 16-bit offset among the "command"
+	 * byte and the first data byte.
+	 */
+	return i2c_smbus_write_word_data(client,
+		((offset >> 8) & 0xff),
+		(value << 8) | (offset & 0xff));
+}
+
+/*
  * Write block data to an AT24 device using SMBus cycles.
  */
 static inline s32 at24_smbus_write_i2c_block_data(struct at24_data *at24,

@@ -376,8 +395,8 @@ static ssize_t at24_eeprom_write(struct at24_data *at24, const char *buf,
 						client, offset, count, buf);
 				break;
 			case I2C_SMBUS_BYTE_DATA:
-				status = i2c_smbus_write_byte_data(client,
-						offset, buf[0]);
+				status = at24_smbus_write_byte_data(at24,
+						client, offset, buf[0]);
 				break;
 			}

@@ -562,7 +581,17 @@ static int at24_probe(struct i2c_client *client, const struct i2c_device_id *id)
 		if (i2c_check_functionality(client->adapter,
 				I2C_FUNC_SMBUS_WRITE_I2C_BLOCK)) {
 			use_smbus_write = I2C_SMBUS_I2C_BLOCK_DATA;
-		} else if (i2c_check_functionality(client->adapter,
+		} else if (chip.flags & AT24_FLAG_ADDR16 &&
+		    i2c_check_functionality(client->adapter,
+					I2C_FUNC_SMBUS_WRITE_WORD_DATA)) {
+			/*
+			 * We need SMBUS_WRITE_WORD_DATA to implement
+			 * byte writes for 16-bit address devices.
+			 */
+			use_smbus_write = I2C_SMBUS_BYTE_DATA;
+			chip.page_size = 1;
+		} else if (!(chip.flags & AT24_FLAG_ADDR16) &&
+			i2c_check_functionality(client->adapter,
 				I2C_FUNC_SMBUS_WRITE_BYTE_DATA)) {
 			use_smbus_write = I2C_SMBUS_BYTE_DATA;
 			chip.page_size = 1;

Signature · 1 line

1.9.1

Jean Delvare

2015-11-03 08:43 UTC #4 lore raw

In reply to Aaron Sierra

Quoted 23 lines · Aaron Sierra

Introduce at24_smbus_write_byte_data() to allow very slow (e.g. 248 B/s) write access to 16-bit EEPROM devices attached to SMBus controllers like the Intel SCH.
Signed-off-by Nate Case <[email protected]>
Signed-off-by Aaron Sierra <[email protected]>
---
 drivers/misc/eeprom/at24.c | 35 ++++++++++++++++++++++++++++++++---
 1 file changed, 32 insertions(+), 3 deletions(-)
drivers/misc/eeprom/at24.c +5 -0
index 4cf53a0..2ee1301 100644
@@ -134,6 +134,25 @@ MODULE_DEVICE_TABLE(i2c, at24_ids);
 /*-------------------------------------------------------------------------*/
 
 /*
+ * Write a byte to an AT24 device using SMBus cycles.
+ */
+static inline s32 at24_smbus_write_byte_data(struct at24_data *at24,
+	struct i2c_client *client, u16 offset, u8 value)
+{

drivers/misc/eeprom/at24.c MODULE_DEVICE_TABLE(i2c, at24_ids); · line 151

Quoted 10 lines

drivers/misc/eeprom/at24.c +10 -0

+	if (!(at24->chip.flags & AT24_FLAG_ADDR16))
+		return i2c_smbus_write_byte_data(client, offset, value);
+
+	/*
+	 * Emulate I2C multi-byte write by using SMBus "write word"
+	 * cycle.  We split up the 16-bit offset among the "command"
+	 * byte and the first data byte.
+	 */
+	return i2c_smbus_write_word_data(client,
+		((offset >> 8) & 0xff),

Useless masking.

Quoted 19 lines

drivers/misc/eeprom/at24.c +6 -2

+		(value << 8) | (offset & 0xff));
+}
+
+/*
  * Write block data to an AT24 device using SMBus cycles.
  */
 static inline s32 at24_smbus_write_i2c_block_data(struct at24_data *at24,

@@ -401,8 +420,8 @@ static ssize_t at24_eeprom_write(struct at24_data *at24, const char *buf,
 						client, offset, count, buf);
 				break;
 			case I2C_SMBUS_BYTE_DATA:
-				status = i2c_smbus_write_byte_data(client,
-						offset, buf[0]);
+				status = at24_smbus_write_byte_data(at24,
+						client, offset, buf[0]);
 				break;
 			}

drivers/misc/eeprom/at24.c static int at24_probe(struct i2c_client *client, const struct i2c_device_id *id) · line 612

Quoted 5 lines

drivers/misc/eeprom/at24.c +1 -1

@@ -590,7 +609,17 @@ static int at24_probe(struct i2c_client *client, const struct i2c_device_id *id)
 		if (i2c_check_functionality(client->adapter,
 				I2C_FUNC_SMBUS_WRITE_I2C_BLOCK)) {
 			use_smbus_write = I2C_SMBUS_I2C_BLOCK_DATA;
-		} else if (i2c_check_functionality(client->adapter,
+		} else if (chip.flags & AT24_FLAG_ADDR16 &&

Parentheses around (x & y) please.

drivers/misc/eeprom/at24.c static int at24_probe(struct i2c_client *client, const struct i2c_device_id *id) · line 614

Quoted 2 lines

drivers/misc/eeprom/at24.c +2 -0

+		    i2c_check_functionality(client->adapter,
+					I2C_FUNC_SMBUS_WRITE_WORD_DATA)) {

Would be good to align this the same way the other two are aligned.

drivers/misc/eeprom/at24.c static int at24_probe(struct i2c_client *client, const struct i2c_device_id *id) · line 625

Quoted 11 lines

drivers/misc/eeprom/at24.c +8 -0

+			/*
+			 * We need SMBUS_WRITE_WORD_DATA to implement
+			 * byte writes for 16-bit address devices.
+			 */
+			use_smbus_write = I2C_SMBUS_BYTE_DATA;
+			chip.page_size = 1;
+		} else if (!(chip.flags & AT24_FLAG_ADDR16) &&
+			i2c_check_functionality(client->adapter,
 				I2C_FUNC_SMBUS_WRITE_BYTE_DATA)) {
 			use_smbus_write = I2C_SMBUS_BYTE_DATA;
 			chip.page_size = 1;

Like patch 1/3, the code you are adding in this patch can't be tested.

Signature · 2 lines

Jean Delvare
SUSE L3 Support