2 files changed, 26 insertions, 9 deletions

diff --git a/Documentation/hwmon/via686a b/Documentation/hwmon/via686a
index b82014cb7c53..a936fb3824b2 100644
--- a/Documentation/hwmon/via686a
+++ b/Documentation/hwmon/via686a
@@ -18,8 +18,9 @@ Authors:
 Module Parameters
 -----------------
 
-force_addr=0xaddr       Set the I/O base address. Useful for Asus A7V boards
-                        that don't set the address in the BIOS. Does not do a
+force_addr=0xaddr       Set the I/O base address. Useful for boards that
+                        don't set the address in the BIOS. Look for a BIOS
+                        upgrade before resorting to this. Does not do a
                         PCI force; the via686a must still be present in lspci.
                         Don't use this unless the driver complains that the
                         base address is not set.
@@ -63,3 +64,15 @@ miss once-only alarms.
 
 The driver only updates its values each 1.5 seconds; reading it more often
 will do no harm, but will return 'old' values.
+
+Known Issues
+------------
+
+This driver handles sensors integrated in some VIA south bridges. It is
+possible that a motherboard maker used a VT82C686A/B chip as part of a
+product design but was not interested in its hardware monitoring features,
+in which case the sensor inputs will not be wired. This is the case of
+the Asus K7V, A7V and A7V133 motherboards, to name only a few of them.
+So, if you need the force_addr parameter, and end up with values which
+don't seem to make any sense, don't look any further: your chip is simply
+not wired for hardware monitoring.
diff --git a/drivers/hwmon/via686a.c b/drivers/hwmon/via686a.c
index 60e94879f415..688ccf924c3a 100644
--- a/drivers/hwmon/via686a.c
+++ b/drivers/hwmon/via686a.c
@@ -589,10 +589,8 @@ static int via686a_detect(struct i2c_adapter *adapter)
         u16 val;
 
         /* 8231 requires multiple of 256, we enforce that on 686 as well */
-        if (force_addr)
-                address = force_addr & 0xFF00;
-
         if (force_addr) {
+                address = force_addr & 0xFF00;
                 dev_warn(&adapter->dev, "forcing ISA address 0x%04X\n",
                          address);
                 if (PCIBIOS_SUCCESSFUL !=
@@ -603,11 +601,17 @@ static int via686a_detect(struct i2c_adapter *adapter)
             pci_read_config_word(s_bridge, VIA686A_ENABLE_REG, &val))
                 return -ENODEV;
         if (!(val & 0x0001)) {
-                dev_warn(&adapter->dev, "enabling sensors\n");
-                if (PCIBIOS_SUCCESSFUL !=
-                    pci_write_config_word(s_bridge, VIA686A_ENABLE_REG,
-                                          val | 0x0001))
+                if (force_addr) {
+                        dev_info(&adapter->dev, "enabling sensors\n");
+                        if (PCIBIOS_SUCCESSFUL !=
+                            pci_write_config_word(s_bridge, VIA686A_ENABLE_REG,
+                                                  val | 0x0001))
+                                return -ENODEV;
+                } else {
+                        dev_warn(&adapter->dev, "sensors disabled - enable "
+                                 "with force_addr=0x%x\n", address);
                         return -ENODEV;
+                }
         }
 
         /* Reserve the ISA region */