On Mon, 2011-09-05 at 05:41 -0400, Donggeun Kim wrote:
> This patch allows to read temperature
> from TMU(Thermal Management Unit) of SAMSUNG EXYNOS4 series of SoC.
>
> Signed-off-by: Donggeun Kim <dg77.kim@xxxxxxxxxxx>
> Signed-off-by: MyungJoo Ham <myungjoo.ham@xxxxxxxxxxx>
> Signed-off-by: Kyungmin Park <kyungmin.park@xxxxxxxxxxx>
Looks pretty good now. Only a whitespace nitpick, and we'll still have
to resolve the uevent issue.
[ ... ]
> diff --git a/Documentation/hwmon/exynos4_tmu b/Documentation/hwmon/exynos4_tmu
> new file mode 100644
> index 0000000..7fe12c1
> --- /dev/null
> +++ b/Documentation/hwmon/exynos4_tmu
> @@ -0,0 +1,81 @@
> +Kernel driver exynos4_tmu
> +=================
> +
> +Supported chips:
> +* ARM SAMSUNG EXYNOS4 series of SoC
> + Prefix: 'exynos4-tmu'
> + Datasheet: Not publicly available
> +
> +Authors: Donggeun Kim <dg77.kim@xxxxxxxxxxx>
> +
> +Description
> +-----------
> +
> +This driver allows to read temperature inside SAMSUNG EXYNOS4 series of SoC.
> +
> +The chip only exposes the measured 8-bit temperature code value
> +through a register.
> +Temperature can be taken from the temperature code.
> +There are three equations converting from temperature to temperature code.
> +
> +The three equations are:
> + 1. Two point trimming
> + Tc = (T - 25) * (TI2 - TI1) / (85 - 25) + TI1
> +
> + 2. One point trimming
> + Tc = T + TI1 - 25
> +
> + 3. No trimming
> + Tc = T + 50
> +
The above assignment lines create a whitespace warning (blank before
tab). Please fix.
[ ... ]
> +
> +static void exynos4_tmu_work(struct work_struct *work)
> +{
> + struct exynos4_tmu_data *data = container_of(work,
> + struct exynos4_tmu_data, irq_work);
> + unsigned int interrupt_stat;
> + char *envp[2];
> +
> + mutex_lock(&data->lock);
> + clk_enable(data->clk);
> +
> + interrupt_stat = readl(data->base + EXYNOS4_TMU_REG_INTSTAT);
> +
> + writel(EXYNOS4_TMU_INTCLEAR_VAL, data->base + EXYNOS4_TMU_REG_INTCLEAR);
> +
> + if (interrupt_stat & EXYNOS4_TMU_TRIG_LEVEL3_MASK) {
> + envp[0] = "TRIG_LEVEL=3";
> + sysfs_notify(&data->hwmon_dev->kobj, NULL,
> + "temp1_emergency_alarm");
> + } else if (interrupt_stat & EXYNOS4_TMU_TRIG_LEVEL2_MASK) {
> + envp[0] = "TRIG_LEVEL=2";
> + sysfs_notify(&data->hwmon_dev->kobj, NULL,
> + "temp1_crit_alarm");
> + } else if (interrupt_stat & EXYNOS4_TMU_TRIG_LEVEL1_MASK) {
> + envp[0] = "TRIG_LEVEL=1";
> + sysfs_notify(&data->hwmon_dev->kobj, NULL, "temp1_max_alarm");
> + } else
> + envp[0] = "TRIG_LEVEL=0";
> + envp[1] = NULL;
> +
> + kobject_uevent_env(&data->hwmon_dev->kobj, KOBJ_CHANGE, envp);
> +
Concern here is two-fold: envp is driver specific, and sysfs_notify()
should really be called whenever an attribute changes its state. Right
now it is only called for 0->1 transitions, but not for 1->0
transitions, which means that any listener will not get notified for
1->0 transitions. This makes the sysfs notification pretty much useless.
For the uevent, I would suggest to generate the global uevent as other
drivers do it right now.
kobject_uevent(&data->hwmon_dev->kobj, KOBJ_CHANGE);
An alternative would be to pass one of the changed attribute names as
environment (eg the highest temperature 0->1 transition).
For the 1->0 transitions, I don't really have a good idea how to handle
it if the chip does not generate interrupts in this case. Not really
sure, though, if calling sysfs_notify even makes sense in that case,
since a poll on a "triggered" attribute file will be stuck forever.
Thanks,
Guenter
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