On 23 July 2014 12:54, Thierry Reding <thierry.reding@xxxxxxxxx> wrote: > ARM_TEGRA_CPUFREQ is still optional, so the select only applies when the > Tegra cpufreq driver is enabled. This is mostly just out of convenience, > though. The Tegra cpufreq driver uses the generic CPU0 cpufreq driver so > a select will automatically pull in the necessary dependency. With a Not necessarily. cpufreq-cpu0 can have few unmet dependency. And so there are chances that tegra driver is compiled but cpufreq-cpu0 isn't as we didn't mention it as a *hard* dependency. And so at boot, there wouldn't be any cpufreq support even when tegra's cpufreq driver is available. Though, menuconfig may give some warnings no such situations. > "depends on" the Tegra cpufreq driver only becomes available after > you've selected GENERIC_CPUFREQ_CPU0, which is somewhat unintuitive. > > To illustrate with an example: as a user, I want to enable CPU frequency > scaling on Tegra. So I use menuconfig to navigate to the "CPU Frequency > scaling" menu (enable it if not available yet) and look for an entry > that says "Tegra". But I can't find it because it's hidden due to the > lack of GENERIC_CPUFREQ_CPU0. That the Tegra CPU frequency driver uses a > generic driver is an implementation detail that users shouldn't have to > be aware of. Don't know, the guy compiling out stuff should be knowledgeable enough to have a look why tegra cpufreq entry isn't shown in menu. As, probably the above problem I mentioned looks to be of more significance than this one, atleast to me :) And, another thing to mention is that CONFIG_TEGRA_CPUFREQ is valid for earlier platforms as well and so a select/depends wouldn't be valid for earlier platforms. We probably need another Kconfig entry here. > But we're using cpu_dev->of_node, so we need to make sure cpu_dev > doesn't go away suddenly. Simply keeping a reference to ->of_node > won't ensure that. Oh, yeah I completely agree, but don't see that as a normal code style people follow. Probably they take cpu for granted, which doesn't look right :) > I guess technically it would be better if get_cpu_device() already > incremented the reference count on the returned struct device. Currently > it would theoretically still be possible for the device to disappear > between the call to get_cpu_device() and a call to get_device(). I agree again. -- To unsubscribe from this list: send the line "unsubscribe linux-tegra" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
