Re: [PATCH 3/6] hwmon: (dell-smm) Disallow fan_type() calls on broken machines

[Guenter Roeck]

On 06/17/2016 03:54 PM, Pali RohÃr wrote:
> 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@xxxxxxxxx>
> Signed-off-by: Pali RohÃr <pali.rohar@xxxxxxxxx>
> Link: https://bugzilla.kernel.org/show_bug.cgi?id=100121
> Cc: stable@xxxxxxxxxxxxxxx # v4.0+, will need backport

Applied.

It seemed worthwhile to apply this patch now, without waiting for further test
feedback, since it at least reduces the impact of the observed problems.
If follow-up changes are necessary, those will have to be applied in separate
patches.

Guenter

> ---
>   drivers/hwmon/dell-smm-hwmon.c |   36 +++++++++++++++++++++++++-----------
>   1 file changed, 25 insertions(+), 11 deletions(-)
>
> diff --git a/drivers/hwmon/dell-smm-hwmon.c b/drivers/hwmon/dell-smm-hwmon.c
> index c8bd3fdd..4bbc587 100644
> --- 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),