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Date: Thu, 14 Nov 2019 13:39:01 -0800
From: Guenter Roeck <linux@...ck-us.net>
To: Giovanni Mascellani <gio@...ian.org>
Cc: Pali Rohár <pali.rohar@...il.com>,
Jean Delvare <jdelvare@...e.com>, linux-hwmon@...r.kernel.org,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH] hwmon: (dell-smm-hwmon) Disable BIOS fan control on
SET_FAN
On Thu, Nov 14, 2019 at 10:14:08PM +0100, Giovanni Mascellani wrote:
> On some Dell laptops the BIOS directly controls fan speed, ignoring
> SET_FAN commands. Also, the BIOS controller often happens to be buggy,
> failing to increase fan speed when the CPU is under heavy load and
> setting fan at full speed even when the CPU is idle and relatively
> cool.
>
> Disable BIOS fan control on such laptops as soon as a SET_FAN command
> is issued, and re-enable it at module unloading, so that a userspace
> controller like i8kmon can take control of the fan.
>
> There is a missing feature: interaction with PM; I think that when
> suspending on RAM the fans should be stopped (this BIOS doesn't always
> do this automatically, neither when fan control is enabled nor when it
> is disabled); when recovering from hibernation to disk, also, the
> command to disable BIOS fan control should be issued again, because
> the computer will have had a power cycle in the meantime.
>
> I don't know how to implement these two actions; can someone suggest a
> way? Also, I would be happy to know from more experienced people if
> these actions are sensible.
>
I think this is too drastic: Not everyone wants to use this driver for
fan control, and even automatic switching to manual mode on write
operations may be unexpected.
I can see two possibilities: Either add a pwm1_enable attribute to
be able to set manual/automatic fan control, or add a module parameter
to enable manual fan speed control on affected systems.
As for PM support, this would have to be implemented using the standard
PM functions.
Guenter
> Signed-off-by: Giovanni Mascellani <gio@...ian.org>
> ---
> drivers/hwmon/dell-smm-hwmon.c | 64 ++++++++++++++++++++++++++++++++++
> 1 file changed, 64 insertions(+)
>
> diff --git a/drivers/hwmon/dell-smm-hwmon.c b/drivers/hwmon/dell-smm-hwmon.c
> index 4212d022d253..6d72e207076f 100644
> --- a/drivers/hwmon/dell-smm-hwmon.c
> +++ b/drivers/hwmon/dell-smm-hwmon.c
> @@ -32,6 +32,12 @@
>
> #include <linux/i8k.h>
>
> +/*
> + * The code for enabling and disabling BIOS fan control were found by
> + * trial and error with the program at
> + * https://github.com/clopez/dellfan.
> + */
> +
> #define I8K_SMM_FN_STATUS 0x0025
> #define I8K_SMM_POWER_STATUS 0x0069
> #define I8K_SMM_SET_FAN 0x01a3
> @@ -43,6 +49,8 @@
> #define I8K_SMM_GET_TEMP_TYPE 0x11a3
> #define I8K_SMM_GET_DELL_SIG1 0xfea3
> #define I8K_SMM_GET_DELL_SIG2 0xffa3
> +#define I8K_SMM_DISABLE_BIOS 0x30a3
> +#define I8K_SMM_ENABLE_BIOS 0x31a3
>
> #define I8K_FAN_MULT 30
> #define I8K_FAN_MAX_RPM 30000
> @@ -68,6 +76,8 @@ static uint i8k_pwm_mult;
> static uint i8k_fan_max = I8K_FAN_HIGH;
> static bool disallow_fan_type_call;
> static bool disallow_fan_support;
> +static bool disable_bios;
> +static bool bios_disabled;
>
> #define I8K_HWMON_HAVE_TEMP1 (1 << 0)
> #define I8K_HWMON_HAVE_TEMP2 (1 << 1)
> @@ -419,6 +429,26 @@ static int i8k_get_power_status(void)
> return (regs.eax & 0xff) == I8K_POWER_AC ? I8K_AC : I8K_BATTERY;
> }
>
> +/*
> + * Disable BIOS fan control.
> + */
> +static int i8k_disable_bios(void)
> +{
> + struct smm_regs regs = { .eax = I8K_SMM_DISABLE_BIOS, .ebx = 0 };
> +
> + return i8k_smm(®s) ? : regs.eax & 0xff;
> +}
> +
> +/*
> + * Enable BIOS fan control.
> + */
> +static int i8k_enable_bios(void)
> +{
> + struct smm_regs regs = { .eax = I8K_SMM_ENABLE_BIOS, .ebx = 0 };
> +
> + return i8k_smm(®s) ? : regs.eax & 0xff;
> +}
> +
> /*
> * Procfs interface
> */
> @@ -488,6 +518,13 @@ i8k_ioctl_unlocked(struct file *fp, unsigned int cmd, unsigned long arg)
> if (copy_from_user(&speed, argp + 1, sizeof(int)))
> return -EFAULT;
>
> + if (disable_bios && !bios_disabled) {
> + val = i8k_disable_bios();
> + if (val < 0)
> + return val;
> + bios_disabled = true;
> + }
> +
> val = i8k_set_fan(val, speed);
> break;
>
> @@ -1135,6 +1172,22 @@ static struct dmi_system_id i8k_blacklist_fan_support_dmi_table[] __initdata = {
> { }
> };
>
> +/*
> + * On some machines the BIOS disregards all SET_FAN commands unless it
> + * is explicitly disabled.
> + * See bug: https://bugzilla.kernel.org/show_bug.cgi?id=200949
> + */
> +static struct dmi_system_id i8k_disable_bios_dmi_table[] __initdata = {
> + {
> + .ident = "Dell Precision 5530",
> + .matches = {
> + DMI_MATCH(DMI_SYS_VENDOR, "Dell Inc."),
> + DMI_EXACT_MATCH(DMI_PRODUCT_NAME, "Precision 5530"),
> + },
> + },
> + { }
> +};
> +
> /*
> * Probe for the presence of a supported laptop.
> */
> @@ -1169,6 +1222,11 @@ static int __init i8k_probe(void)
> disallow_fan_type_call = true;
> }
>
> + if (dmi_check_system(i8k_disable_bios_dmi_table)) {
> + pr_warn("broken Dell BIOS detected, will disable BIOS fan control\n");
The above is your interpretation: Since there is a command to enable/disable
BIOS fan control, we can not just claim that it is broken because we don't like
how it works.
> + disable_bios = true;
> + }
> +
> strlcpy(bios_version, i8k_get_dmi_data(DMI_BIOS_VERSION),
> sizeof(bios_version));
> strlcpy(bios_machineid, i8k_get_dmi_data(DMI_PRODUCT_SERIAL),
> @@ -1241,6 +1299,12 @@ static void __exit i8k_exit(void)
> {
> hwmon_device_unregister(i8k_hwmon_dev);
> i8k_exit_procfs();
> +
> + if (bios_disabled) {
> + pr_warn("re-enabling BIOS fan control\n");
I don't see the point of this warning.
> + if (i8k_enable_bios())
> + pr_warn("could not re-enable BIOS fan control\n");
> + }
> }
>
> module_init(i8k_init);
> --
> 2.24.0
>
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