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    SubjectRe: [PATCH 2/3] thermal: sun50i: add thermal driver for h6
    Hi,

    On Sun, May 12, 2019 at 11:41:28PM +0200, Ondřej Jirman wrote:
    > > > +static int tsens_get_temp(void *data, int *temp)
    > > > +{
    > > > + struct tsensor *s = data;
    > > > + struct tsens_device *tmdev = s->tmdev;
    > > > + int val;
    > > > +
    > > > + regmap_read(tmdev->regmap, tmdev->chip->temp_data_base +
    > > > + 0x4 * s->id, &val);
    > > > +
    > > > + if (unlikely(val == 0))
    > > > + return -EBUSY;
    > >
    > > I'm not sure why a val equals to 0 would be associated with EBUSY?
    >
    > Thermal zone driver can (will) call get_temp before we got the
    > first interrupt and the thermal data. In that case val will be 0.
    >
    > Resulting in:
    >
    > (val + offset) * scale = (-2794) * -67 = 187198
    >
    > 187°C and immediate shutdown during boot - based on cirtical
    > temperature being reached.
    >
    > Busy here means, get_temp does not yet have data. Thermal zone
    > driver just reports any error to dmesg output.

    Ah, that makes sense.

    I guess if we're switching to an interrupt-based driver, then we can
    just use a waitqueue, or is get_temp supposed to be atomic?

    Maxime

    --
    Maxime Ripard, Bootlin
    Embedded Linux and Kernel engineering
    https://bootlin.com
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