On Tue, Sep 04, 2007 at 02:47:50PM +0400, Anton Vorontsov wrote: > > _and system GPIOs_ :-) > > Yup, firmware should set up gpios, to make initial kernel boot.
No, it should set all pins and similar setup-once type initialization that is board-specific rather than device-specific -- there's no reason for the kernel to need to care about that sort of thing. > After that, kernel can and should manage GPIOs. Few examples. > > Say units (like USB or SPI) can work in very different modes. And > it's okay if user want to change device mode in the runtime. This is a special case that warrants kernel involvement. It should not be used as justification for the bootloader leaving pins unconfigured in the majority of cases where it does not make sense to change them at runtime. > Another example, power management - if some unit temporarily unused, > to save power GPIOs should be set up differently. Say if SPI unit > turned off (unused just now), it's wise to bring their dedicated > GPIOs to "power saving" state (be it output0/1 or input, it > depends). The kernel is of course welcome to do so -- and this may be a valid reason to attach pin information to specific device nodes, if it actually saves a non-negligible amount of power -- but it's not a reason to force the kernel to have to care by not setting things up in the firmware. -Scott _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@ozlabs.org https://ozlabs.org/mailman/listinfo/linuxppc-dev
