hwmon: (dell-smm) Disallow fan_type() calls on broken machines

Some Dell machines have especially broken SMM or BIOS which cause that once
fan_type() is called then CPU fan speed going randomly up and down. And for
fixing this behaviour reboot is required.

So this patch creates fan_type blacklist of affected Dell machines and
disallow fan_type() call on them to prevent that erratic behaviour.

Old blacklist which disabled loading driver on some machines added in
commits a4b45b25f18d ("hwmon: (dell-smm) Blacklist Dell Studio XPS 8100")
and 6220f4ebd7b4 ("hwmon: (dell-smm) Blacklist Dell Studio XPS 8000") were
moved to FAN_TYPE blacklist.

Reported-by: Jan C Peters <jcpeters89@gmail.com>
Signed-off-by: Pali Rohár <pali.rohar@gmail.com>
Link: https://bugzilla.kernel.org/show_bug.cgi?id=100121
Cc: stable@vger.kernel.org # v4.0+, will need backport
Signed-off-by: Guenter Roeck <linux@roeck-us.net>

diff --git a/drivers/hwmon/dell-smm-hwmon.c b/drivers/hwmon/dell-smm-hwmon.c
index c8bd3fdd07103bdf0d61f0a4d48a5eb1a6134764..4bbc587148685ec4a3bb0fa1eb521b815382119b 100644 (file)
--- a/drivers/hwmon/dell-smm-hwmon.c
+++ b/drivers/hwmon/dell-smm-hwmon.c
@@ -73,6 +73,7 @@ static u32 i8k_hwmon_flags;
 static uint i8k_fan_mult = I8K_FAN_MULT;
 static uint i8k_pwm_mult;
 static uint i8k_fan_max = I8K_FAN_HIGH;
+static bool disallow_fan_type_call;
 
 #define I8K_HWMON_HAVE_TEMP1   (1 << 0)
 #define I8K_HWMON_HAVE_TEMP2   (1 << 1)
@@ -241,6 +242,9 @@ static int i8k_get_fan_type(int fan)
 {
        struct smm_regs regs = { .eax = I8K_SMM_GET_FAN_TYPE, };
 
+       if (disallow_fan_type_call)
+               return -EINVAL;
+
        regs.ebx = fan & 0xff;
        return i8k_smm(&regs) ? : regs.eax & 0xff;
 }
@@ -726,6 +730,9 @@ static struct attribute *i8k_attrs[] = {
 static umode_t i8k_is_visible(struct kobject *kobj, struct attribute *attr,
                              int index)
 {
+       if (disallow_fan_type_call &&
+           (index == 9 || index == 12))
+               return 0;
        if (index >= 0 && index <= 1 &&
            !(i8k_hwmon_flags & I8K_HWMON_HAVE_TEMP1))
                return 0;
@@ -937,12 +944,14 @@ static struct dmi_system_id i8k_dmi_table[] __initdata = {
 
 MODULE_DEVICE_TABLE(dmi, i8k_dmi_table);
 
-static struct dmi_system_id i8k_blacklist_dmi_table[] __initdata = {
+/*
+ * On some machines once I8K_SMM_GET_FAN_TYPE is issued then CPU fan speed
+ * randomly going up and down due to bug in Dell SMM or BIOS. Here is blacklist
+ * of affected Dell machines for which we disallow I8K_SMM_GET_FAN_TYPE call.
+ * See bug: https://bugzilla.kernel.org/show_bug.cgi?id=100121
+ */
+static struct dmi_system_id i8k_blacklist_fan_type_dmi_table[] __initdata = {
        {
-               /*
-                * CPU fan speed going up and down on Dell Studio XPS 8000
-                * for unknown reasons.
-                */
                .ident = "Dell Studio XPS 8000",
                .matches = {
                        DMI_EXACT_MATCH(DMI_SYS_VENDOR, "Dell Inc."),
@@ -950,16 +959,19 @@ static struct dmi_system_id i8k_blacklist_dmi_table[] __initdata = {
                },
        },
        {
-               /*
-                * CPU fan speed going up and down on Dell Studio XPS 8100
-                * for unknown reasons.
-                */
                .ident = "Dell Studio XPS 8100",
                .matches = {
                        DMI_EXACT_MATCH(DMI_SYS_VENDOR, "Dell Inc."),
                        DMI_EXACT_MATCH(DMI_PRODUCT_NAME, "Studio XPS 8100"),
                },
        },
+       {
+               .ident = "Dell Inspiron 580",
+               .matches = {
+                       DMI_EXACT_MATCH(DMI_SYS_VENDOR, "Dell Inc."),
+                       DMI_EXACT_MATCH(DMI_PRODUCT_NAME, "Inspiron 580 "),
+               },
+       },
        { }
 };
 
@@ -974,8 +986,7 @@ static int __init i8k_probe(void)
        /*
         * Get DMI information
         */
-       if (!dmi_check_system(i8k_dmi_table) ||
-           dmi_check_system(i8k_blacklist_dmi_table)) {
+       if (!dmi_check_system(i8k_dmi_table)) {
                if (!ignore_dmi && !force)
                        return -ENODEV;
 
@@ -986,6 +997,9 @@ static int __init i8k_probe(void)
                        i8k_get_dmi_data(DMI_BIOS_VERSION));
        }
 
+       if (dmi_check_system(i8k_blacklist_fan_type_dmi_table))
+               disallow_fan_type_call = true;
+
        strlcpy(bios_version, i8k_get_dmi_data(DMI_BIOS_VERSION),
                sizeof(bios_version));
        strlcpy(bios_machineid, i8k_get_dmi_data(DMI_PRODUCT_SERIAL),