hwmon: (pmbus/fsp-3y) Fix FSP-3Y YH-5151E VOUT

After testing new YH-5151E devices, we found out that not all YH-5151E
work the same. The newly tested devices actually report vout correctly
in linear16 (even though they're still YH-5151E). We suspect that it is
because these new devices have a different firmware version, but that is
unconfirmed. The version cannot be queried through PMBus.

The compliant versions of YH-5151E report VOUT_MODE normally, so we turn
on the linear11 workaround only if VOUT_MODE doesn't report anything.

Signed-off-by: Václav Kubernát <kubernat@cesnet.cz>
Link: https://lore.kernel.org/r/20210513201110.313523-1-kubernat@cesnet.cz
Signed-off-by: Guenter Roeck <linux@roeck-us.net>

diff --git a/drivers/hwmon/pmbus/fsp-3y.c b/drivers/hwmon/pmbus/fsp-3y.c
index e2484247525452ab2b9870e578df196aabbbfed9..aec294cc72d1f249743cf8549184eb309ae67b83 100644 (file)
--- a/drivers/hwmon/pmbus/fsp-3y.c
+++ b/drivers/hwmon/pmbus/fsp-3y.c
@@ -37,6 +37,8 @@ struct fsp3y_data {
        struct pmbus_driver_info info;
        int chip;
        int page;
+
+       bool vout_linear_11;
 };
 
 #define to_fsp3y_data(x) container_of(x, struct fsp3y_data, info)
@@ -108,11 +110,9 @@ static int fsp3y_read_byte_data(struct i2c_client *client, int page, int reg)
        int rv;
 
        /*
-        * YH5151-E outputs vout in linear11. The conversion is done when
-        * reading. Here, we have to inject pmbus_core with the correct
-        * exponent (it is -6).
+        * Inject an exponent for non-compliant YH5151-E.
         */
-       if (data->chip == yh5151e && reg == PMBUS_VOUT_MODE)
+       if (data->vout_linear_11 && reg == PMBUS_VOUT_MODE)
                return 0x1A;
 
        rv = set_page(client, page);
@@ -161,10 +161,9 @@ static int fsp3y_read_word_data(struct i2c_client *client, int page, int phase,
                return rv;
 
        /*
-        * YH-5151E is non-compliant and outputs output voltages in linear11
-        * instead of linear16.
+        * Handle YH-5151E non-compliant linear11 vout voltage.
         */
-       if (data->chip == yh5151e && reg == PMBUS_READ_VOUT)
+       if (data->vout_linear_11 && reg == PMBUS_READ_VOUT)
                rv = sign_extend32(rv, 10) & 0xffff;
 
        return rv;
@@ -256,6 +255,25 @@ static int fsp3y_probe(struct i2c_client *client)
 
        data->info = fsp3y_info[data->chip];
 
+       /*
+        * YH-5151E sometimes reports vout in linear11 and sometimes in
+        * linear16. This depends on the exact individual piece of hardware. One
+        * YH-5151E can use linear16 and another might use linear11 instead.
+        *
+        * The format can be recognized by reading VOUT_MODE - if it doesn't
+        * report a valid exponent, then vout uses linear11. Otherwise, the
+        * device is compliant and uses linear16.
+        */
+       data->vout_linear_11 = false;
+       if (data->chip == yh5151e) {
+               rv = i2c_smbus_read_byte_data(client, PMBUS_VOUT_MODE);
+               if (rv < 0)
+                       return rv;
+
+               if (rv == 0xFF)
+                       data->vout_linear_11 = true;
+       }
+
        return pmbus_do_probe(client, &data->info);
 }