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

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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: Armin Wolf <W_Armin@gmx.de>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
This commit is contained in:
Guenter Roeck 2024-06-14 08:27:21 -07:00
parent 27972a4142
commit 1226a1b2e5
1 changed files with 56 additions and 0 deletions
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56
drivers/hwmon/spd5118.c
View File

@ -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;