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Date: Wed, 19 May 2021 16:11:04 -0700
From: Guenter Roeck <linux@...ck-us.net>
To: Václav Kubernát <kubernat@...net.cz>,
Jean Delvare <jdelvare@...e.com>,
Jonathan Corbet <corbet@....net>, linux-hwmon@...r.kernel.org,
linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v5 2/5] hwmon: (max31790) Fix and split pwm*_enable
On 5/11/21 6:30 PM, Václav Kubernát wrote:
> In the old code, pwm*_enable does two things. Firstly, it sets whether
> the chip should run in PWM or RPM mode. Secondly, it tells the chip
> whether it should monitor fan RPM. However, these two settings aren't
> tied together, so they shouldn't be set with a single value. In the new
> code, fan*_enable now controls fan RPM monitoring (pwm*_enable no longer
> controls that).
>
> According to the sysfs hwmon documentation, pwm*_enable has three
> possible values, 0 for "no control / full-speed", 1 for manual mode, and
> 2+ for automatic. The old code works fine for 1 and 2, but 0 only
> differs from 1 in that it just turns off fan speed monitoring. The chip
> actually does have a way to turn off fan controls (and only monitor),
> and what that does is that it sets PWM to 0% duty cycle. In the new
> code, 0 in pwm*_enable turns off the "control" feature of the chip.
>
> These two changes are closely connected together, mainly because the
> detection of the pwm*_enable value depended on whether fan speed
> monitoring is enabled (which is now controlled as written in the first
> paragraph).
>
The above is an indication that the current code is simply wrong.
pwmX_enable does not and should not have anything to do with
fan speed monitoring (even though it may implicitly enable it).
Fixing pwmX_enable therefore needs to be a separate patch from
introducing fanX_enable, and like the other fixes it needs to come
first, before changing the code to use regmap (to enable backporting).
More comments below.
Thanks,
Guenter
> Signed-off-by: Václav Kubernát <kubernat@...net.cz>
> ---
> Documentation/hwmon/max31790.rst | 10 ++--
> drivers/hwmon/max31790.c | 78 +++++++++++++++++++++-----------
> 2 files changed, 58 insertions(+), 30 deletions(-)
>
> diff --git a/Documentation/hwmon/max31790.rst b/Documentation/hwmon/max31790.rst
> index f301385d8cef..d2ac4e926905 100644
> --- a/Documentation/hwmon/max31790.rst
> +++ b/Documentation/hwmon/max31790.rst
> @@ -34,10 +34,14 @@ also be configured to serve as tachometer inputs.
> Sysfs entries
> -------------
>
> -================== === =======================================================
> +================== === =============================================================
> +fan[1-12]_enable RW enable fan speed monitoring
> fan[1-12]_input RO fan tachometer speed in RPM
> fan[1-12]_fault RO fan experienced fault
> fan[1-6]_target RW desired fan speed in RPM
> -pwm[1-6]_enable RW regulator mode, 0=disabled, 1=manual mode, 2=rpm mode
> +pwm[1-6]_enable RW regulator mode, 0=no control, sets 0% PWM,
> + 1=manual (pwm) mode,
> + 2=rpm mode
> + setting rpm mode sets fan*_enable to 1
> pwm[1-6] RW fan target duty cycle (0-255)
> -================== === =======================================================
> +================== === =============================================================
> diff --git a/drivers/hwmon/max31790.c b/drivers/hwmon/max31790.c
> index e3765ce4444a..5d4c551df010 100644
> --- a/drivers/hwmon/max31790.c
> +++ b/drivers/hwmon/max31790.c
> @@ -30,6 +30,7 @@
> #define MAX31790_FAN_CFG_RPM_MODE 0x80
> #define MAX31790_FAN_CFG_TACH_INPUT_EN 0x08
> #define MAX31790_FAN_CFG_TACH_INPUT 0x01
> +#define MAX31790_FAN_CFG_CTRL_MON 0x10
This define should be above MAX31790_FAN_CFG_TACH_INPUT_EN
to maintain sequence/order.
>
> /* Fan Dynamics register bits */
> #define MAX31790_FAN_DYN_SR_SHIFT 5
> @@ -191,6 +192,9 @@ static int max31790_read_fan(struct device *dev, u32 attr, int channel,
> else
> *val = !!(fault & (1 << channel));
> return 0;
> + case hwmon_fan_enable:
> + *val = !!(data->fan_config[channel] & MAX31790_FAN_CFG_TACH_INPUT_EN);
> + return 0;
> default:
> return -EOPNOTSUPP;
> }
> @@ -233,6 +237,15 @@ static int max31790_write_fan(struct device *dev, u32 attr, int channel,
> MAX31790_REG_TARGET_COUNT(channel),
> target_count);
> break;
> + case hwmon_fan_enable:
> + if (val == 0)
> + data->fan_config[channel] &= ~MAX31790_FAN_CFG_TACH_INPUT_EN;
> + else
> + data->fan_config[channel] |= MAX31790_FAN_CFG_TACH_INPUT_EN;
> + err = regmap_write(regmap,
> + MAX31790_REG_FAN_CONFIG(channel),
> + data->fan_config[channel]);
> + break;
> default:
> err = -EOPNOTSUPP;
> break;
> @@ -260,6 +273,11 @@ static umode_t max31790_fan_is_visible(const void *_data, u32 attr, int channel)
> !(fan_config & MAX31790_FAN_CFG_TACH_INPUT))
> return 0644;
> return 0;
> + case hwmon_fan_enable:
> + if (channel < NR_CHANNEL ||
> + (fan_config & MAX31790_FAN_CFG_TACH_INPUT))
> + return 0644;
> + return 0;
> default:
> return 0;
> }
> @@ -281,12 +299,12 @@ static int max31790_read_pwm(struct device *dev, u32 attr, int channel,
> *val = read >> 8;
> return 0;
> case hwmon_pwm_enable:
> - if (data->fan_config[channel] & MAX31790_FAN_CFG_RPM_MODE)
> + if (data->fan_config[channel] & MAX31790_FAN_CFG_CTRL_MON)
> + *val = 0;
> + else if (data->fan_config[channel] & MAX31790_FAN_CFG_RPM_MODE)
> *val = 2;
> - else if (data->fan_config[channel] & MAX31790_FAN_CFG_TACH_INPUT_EN)
> + else
> *val = 1;
> - else
> - *val = 0;
> return 0;
> default:
> return -EOPNOTSUPP;
> @@ -298,35 +316,41 @@ static int max31790_write_pwm(struct device *dev, u32 attr, int channel,
> {
> struct max31790_data *data = dev_get_drvdata(dev);
> struct regmap *regmap = data->regmap;
> - u8 fan_config;
> + u8 fan_config = data->fan_config[channel];
> int err = 0;
>
> mutex_lock(&data->update_lock);
>
> switch (attr) {
> case hwmon_pwm_input:
> - if (val < 0 || val > 255) {
> + if (fan_config & MAX31790_FAN_CFG_CTRL_MON || val < 0 || val > 255) {
No. It has to be possible to set the target pwm value before enabling pwm control.
> err = -EINVAL;
> break;
> }
> +
> err = write_reg_word(regmap, MAX31790_REG_PWMOUT(channel), val << 8);
> break;
> case hwmon_pwm_enable:
> fan_config = data->fan_config[channel];
> - if (val == 0) {
> - fan_config &= ~(MAX31790_FAN_CFG_TACH_INPUT_EN |
> - MAX31790_FAN_CFG_RPM_MODE);
> - } else if (val == 1) {
> - fan_config = (fan_config |
> - MAX31790_FAN_CFG_TACH_INPUT_EN) &
> - ~MAX31790_FAN_CFG_RPM_MODE;
> + if (val == 0)
> + fan_config |= MAX31790_FAN_CFG_CTRL_MON;
> + else if (val == 1) {
> + fan_config &= ~(MAX31790_FAN_CFG_RPM_MODE | MAX31790_FAN_CFG_CTRL_MON);
> } else if (val == 2) {
> - fan_config |= MAX31790_FAN_CFG_TACH_INPUT_EN |
> - MAX31790_FAN_CFG_RPM_MODE;
> + fan_config &= ~(MAX31790_FAN_CFG_CTRL_MON);
Unnecessary ( )
> + fan_config |= MAX31790_FAN_CFG_RPM_MODE;
> } else {
> err = -EINVAL;
> break;
> }
> +
> + /*
> + * RPM mode implies enabled TACH input, so enable it in RPM
> + * mode.
> + */
> + if (val == 2)
> + fan_config |= MAX31790_FAN_CFG_TACH_INPUT_EN;
> +
The datasheet says this is automatically enabled in rpm mode, meaning there
is no need to explicitly set the bit. I don't know if the bit is set
automatically. If not, it should not be set here. Either case, there is
already an "if (val ==2)" check above. If needed, this bit should be set there.
> data->fan_config[channel] = fan_config;
> err = regmap_write(regmap,
> MAX31790_REG_FAN_CONFIG(channel),
> @@ -400,18 +424,18 @@ static umode_t max31790_is_visible(const void *data,
>
> static const struct hwmon_channel_info *max31790_info[] = {
> HWMON_CHANNEL_INFO(fan,
> - HWMON_F_INPUT | HWMON_F_TARGET | HWMON_F_FAULT,
> - HWMON_F_INPUT | HWMON_F_TARGET | HWMON_F_FAULT,
> - HWMON_F_INPUT | HWMON_F_TARGET | HWMON_F_FAULT,
> - HWMON_F_INPUT | HWMON_F_TARGET | HWMON_F_FAULT,
> - HWMON_F_INPUT | HWMON_F_TARGET | HWMON_F_FAULT,
> - HWMON_F_INPUT | HWMON_F_TARGET | HWMON_F_FAULT,
> - HWMON_F_INPUT | HWMON_F_FAULT,
> - HWMON_F_INPUT | HWMON_F_FAULT,
> - HWMON_F_INPUT | HWMON_F_FAULT,
> - HWMON_F_INPUT | HWMON_F_FAULT,
> - HWMON_F_INPUT | HWMON_F_FAULT,
> - HWMON_F_INPUT | HWMON_F_FAULT),
> + HWMON_F_ENABLE | HWMON_F_INPUT | HWMON_F_TARGET | HWMON_F_FAULT,
> + HWMON_F_ENABLE | HWMON_F_INPUT | HWMON_F_TARGET | HWMON_F_FAULT,
> + HWMON_F_ENABLE | HWMON_F_INPUT | HWMON_F_TARGET | HWMON_F_FAULT,
> + HWMON_F_ENABLE | HWMON_F_INPUT | HWMON_F_TARGET | HWMON_F_FAULT,
> + HWMON_F_ENABLE | HWMON_F_INPUT | HWMON_F_TARGET | HWMON_F_FAULT,
> + HWMON_F_ENABLE | HWMON_F_INPUT | HWMON_F_TARGET | HWMON_F_FAULT,
> + HWMON_F_ENABLE | HWMON_F_INPUT | HWMON_F_FAULT,
> + HWMON_F_ENABLE | HWMON_F_INPUT | HWMON_F_FAULT,
> + HWMON_F_ENABLE | HWMON_F_INPUT | HWMON_F_FAULT,
> + HWMON_F_ENABLE | HWMON_F_INPUT | HWMON_F_FAULT,
> + HWMON_F_ENABLE | HWMON_F_INPUT | HWMON_F_FAULT,
> + HWMON_F_ENABLE | HWMON_F_INPUT | HWMON_F_FAULT),
> HWMON_CHANNEL_INFO(pwm,
> HWMON_PWM_INPUT | HWMON_PWM_ENABLE,
> HWMON_PWM_INPUT | HWMON_PWM_ENABLE,
>
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