Hi, Daniel

Subject: Re: [PATCH RESEND 2/4] thermal: imx8mm: Add support for
i.MX8MM thermal monitoring unit

On 28/02/2020 02:12, Anson Huang wrote:

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Hi, Daniel

[ ... ]

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+static int tmu_get_temp(void *data, int *temp) {
+	struct imx8mm_tmu *tmu = data;
+	u32 val;
+
+	/* the temp sensor need about 1ms to finish the measurement */
+	usleep_range(1000, 2000);

Why do yo need to force a delay here? If the sensor can not be read
more than one time every 1ms, then specify that in the DT switching
the polling to the right value, no?

The polling time(2 seconds) is OK for this case, adding this sleep is
to prevent user from reading temperature from sysfs interface very

frequently like less than 1ms, does it make sense?

Not really, well except if the user is able to press the keys in less than 1ms :)

If the userspace writes a polling script reading the temperature in a busy loop,
there is nothing we can do against silly programming :/

Make sense😊

However, it could interesting to add a <min polling interval> in the thermal
structure and handle that from the core framework by caching the last value
and return it in case get_temp is called too fast.

OK, I will resend V2 patch set to remove the sleep in this driver and see if there is
real issue of such corner case, if any issue observed, I will try summit a patch to core
framework later.

Thanks,
Anson