Commit 1226a1b2 authored by Guenter Roeck's avatar Guenter Roeck
Browse files

hwmon: (spd5118) Add support for Renesas/ITD SPD5118 hub controllers 



The SPD5118 specification says, in its documentation of the page bits
in the MR11 register:

"
This register only applies to non-volatile memory (1024) Bytes) access of
SPD5 Hub device.
For volatile memory access, this register must be programmed to '000'.
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
"

Renesas/ITD SPD5118 hub controllers take this literally and disable access
to volatile memory if the page selected in MR11 is != 0. Since the BIOS or
ROMMON will access the non-volatile memory and likely select a page != 0,
this means that the driver will not instantiate since it can not identify
the chip. Even if the driver instantiates, access to volatile registers
is blocked after a nvram read operation which selects a page other than 0.

To solve the problem, add initialization code to select page 0 during
probe. Before doing that, use basic validation to ensure that this is
really a SPD5118 device and not some random EEPROM.

Cc: Sasha Kozachuk <skozachuk@google.com>
Cc: John Hamrick <johnham@google.com>
Cc: Chris Sarra <chrissarra@google.com>
Tested-by: default avatarArmin Wolf <W_Armin@gmx.de>
Signed-off-by: default avatarGuenter Roeck <linux@roeck-us.net>
parent 27972a41

drivers/hwmon/spd5118.c

+56 −0
Original line number Diff line number Diff line
@@ -513,6 +513,58 @@ static const struct regmap_config spd5118_regmap_config = { 
	.num_ranges = ARRAY_SIZE(spd5118_regmap_range_cfg),

};



static int spd5118_init(struct i2c_client *client)

{

	struct i2c_adapter *adapter = client->adapter;

	int err, regval, mode;



	if (!i2c_check_functionality(adapter, I2C_FUNC_SMBUS_BYTE_DATA |

				     I2C_FUNC_SMBUS_WORD_DATA))

		return -ENODEV;



	regval = i2c_smbus_read_word_swapped(client, SPD5118_REG_TYPE);

	if (regval < 0 || (regval && regval != 0x5118))

		return -ENODEV;



	/*

	 * If the device type registers return 0, it is possible that the chip

	 * has a non-zero page selected and takes the specification literally,

	 * i.e. disables access to volatile registers besides the page register

	 * if the page is not 0. Try to identify such chips.

	 */

	if (!regval) {

		/* Vendor ID registers must also be 0 */

		regval = i2c_smbus_read_word_data(client, SPD5118_REG_VENDOR);

		if (regval)

			return -ENODEV;



		/* The selected page in MR11 must not be 0 */

		mode = i2c_smbus_read_byte_data(client, SPD5118_REG_I2C_LEGACY_MODE);

		if (mode < 0 || (mode & ~SPD5118_LEGACY_MODE_MASK) ||

		    !(mode & SPD5118_LEGACY_PAGE_MASK))

			return -ENODEV;



		err = i2c_smbus_write_byte_data(client, SPD5118_REG_I2C_LEGACY_MODE,

						mode & SPD5118_LEGACY_MODE_ADDR);

		if (err)

			return -ENODEV;



		/*

		 * If the device type registers are still bad after selecting

		 * page 0, this is not a SPD5118 device. Restore original

		 * legacy mode register value and abort.

		 */

		regval = i2c_smbus_read_word_swapped(client, SPD5118_REG_TYPE);

		if (regval != 0x5118) {

			i2c_smbus_write_byte_data(client, SPD5118_REG_I2C_LEGACY_MODE, mode);

			return -ENODEV;

		}

	}



	/* We are reasonably sure that this is really a SPD5118 hub controller */

	return 0;

}



static int spd5118_probe(struct i2c_client *client)

{

	struct device *dev = &client->dev;
@@ -522,6 +574,10 @@ static int spd5118_probe(struct i2c_client *client) 
	struct regmap *regmap;

	int err;



	err = spd5118_init(client);

	if (err)

		return err;



	data = devm_kzalloc(dev, sizeof(*data), GFP_KERNEL);

	if (!data)

		return -ENOMEM;