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charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 8/20/26 18:06, Changhuang Liang wrote: > Hi, Guenter > > Thanks for the review. > >>>> On 8/19/26 02:16, Changhuang Liang wrote: >>>>> Add fan tach driver for StarFive JHB100 SoC. >>>>> >>>>> The controller supports up to 16 independent fan tachometer inputs >>>>> and reports fan speed in RPM through the hwmon sysfs interface, >>>>> along with stall and low-speed alarms. >>>>> >>>>> For this controller, the special clock and reset operation sequence is: >>>>> probe: clk_prepare_enable() than reset_control_deassert() >>>>> remove: clk_disable_unprepare() than reset_control_assert() >>>> >>>> s/than/then/ >>>> >>>>> >>>>> Co-developed-by: William Qiu >>>>> Signed-off-by: William Qiu >>>>> Signed-off-by: Changhuang Liang >>>>> >>>>> --- >> ... >>>>> + >>>>> +static int starfive_fan_tach_hwmon_read(struct device *dev, >>>>> + enum hwmon_sensor_types type, u32 attr, >>>>> + int channel, long *val) >>>>> +{ >>>>> + struct starfive_fan_tach_data *priv = dev_get_drvdata(dev); >>>>> + int ret = 0; >>>>> + >>>>> + switch (attr) { >>>>> + case hwmon_fan_fault: >>>>> + scoped_guard(mutex, &priv->lock) { >>>>> + scoped_guard(spinlock_irqsave, &priv->irq_lock) { >>>>> + writel(STARFIVE_FAN_TACH_STALL_INT(channel), >>>>> + priv->regs + STARFIVE_FAN_TACH_STATUS); >>>>> + /* clear fan_stall first */ >>>>> + priv->fan_stall[channel] = 0; >>>>> + reinit_completion(&priv->comp_stall[channel]); >>>>> + priv->armed_stall |= BIT(channel); >>>>> + } >>>>> + >>>>> + starfive_fan_tach_ch_stall_unmask(priv, channel, true); >>>>> + >>>>> + /* Waiting for hardware to measure */ >>>>> + >> wait_for_completion_timeout(&priv->comp_stall[channel], >>>>> + 2 * >>>> STARFIVE_FAN_TACH_TIMEOUT_JIFFIES); >>>>> + >>>>> + starfive_fan_tach_ch_stall_unmask(priv, channel, false); >>>>> + >>>>> + scoped_guard(spinlock_irqsave, &priv->irq_lock) { >>>>> + priv->armed_stall &= ~BIT(channel); >>>>> + *val = priv->fan_stall[channel]; >>>>> + } >>>>> + } >>>>> + >>>> >>>> I'd really be interested to see how long it takes to read the alarm >>>> and fault status of all fans. And, yes, Sashiko has a point: the >>>> attributes are supported to report a sticky status, not something >>>> that is calculated on the fly. Is this based on some heuristics ? I >>>> don't claim to understand how fault and min_alarm are calculated. A >>>> comment in the code describing how this works would be helpful. >>> >>> There is no real calculation for fault and min_alarm, the hardware >>> simply counts the corresponding pulses within a specified time period >>> and reports the counts via interrupt when the counting period expires. >>> I will try to modify it so that the previous statistical result is >>> recorded, and when reading, the previous result is returned, thus >> eliminating the need to wait for the measurement. >>> >> >> So how long does it take to execute the "sensors" command with 16 active >> fans ? > > # time sensors > starfive_fan_tach-isa-0000 > Adapter: ISA adapter > fan1: FAULT (min = 300 RPM) > fan2: FAULT (min = 300 RPM) > fan3: FAULT (min = 300 RPM) > fan4: FAULT (min = 300 RPM) > fan5: FAULT (min = 300 RPM) > fan6: FAULT (min = 300 RPM) > fan7: FAULT (min = 300 RPM) > fan8: FAULT (min = 300 RPM) > fan9: FAULT (min = 300 RPM) > fan10: FAULT (min = 300 RPM) > fan11: FAULT (min = 300 RPM) > fan12: FAULT (min = 300 RPM) > fan13: FAULT (min = 300 RPM) > fan14: FAULT (min = 300 RPM) > fan15: FAULT (min = 300 RPM) > fan16: 1800 RPM (min = 300 RPM) > > > real 0m4.865s > user 0m0.023s > sys 0m0.001s > > >> ... >>>>> + >>>>> + for (index = 0; index < count; index++) { >>>>> + u8 ch = tach_ch[index]; >>>>> + >>>>> + if (ch >= STARFIVE_FAN_TACH_CH) { >>>>> + dev_warn(priv->dev, "Invalid tach-ch %d, skipping\n", ch); >>>>> + continue; >>>> >>>> This should also return an error. Also, this is the only use of >>>> priv->dev, and >>>> priv->dev == dev. priv->dev is therefore unnecessary. >>>> >>> >>> Thank you for pointing that out. I noticed that the `struct device >>> *dev` passed in the function >>> starfive_fan_tach_create_fan() is somewhat redundant, so I plan to >>> remove it directly and keep `priv->dev` instead. >> >> Just for use in this function ? Why ? It is not used after probe. > > After probe, priv->dev is also used. In the starfive_fan_tach_create_fan() function, > priv->dev can be used directly as well, so I plan to simply remove struct device *dev. > Are you checking if I pay attention ? starfive_fan_tach_create_fan() is called from the probe function, not "after" probe. Guenter