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@xxxxxxxxxx>
Cc: John Hamrick <johnham@xxxxxxxxxx>
Cc: Chris Sarra <chrissarra@xxxxxxxxxx>
Signed-off-by: Guenter Roeck <linux@xxxxxxxxxxxx>
---
v2: Simplified to use mechanisms introduced in the first two patches
of the series.
drivers/hwmon/spd5118.c | 56 +++++++++++++++++++++++++++++++++++++++++
1 file changed, 56 insertions(+)
diff --git a/drivers/hwmon/spd5118.c b/drivers/hwmon/spd5118.c
index 995c45e2a997..80a02dba2ccc 100644
--- a/drivers/hwmon/spd5118.c
+++ b/drivers/hwmon/spd5118.c
@@ -538,6 +538,58 @@ 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;
@@ -547,6 +599,10 @@ 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;
--
2.39.2
