Dear Andrew Lunn, On Fri, 24 Oct 2014 16:20:44 +0200, Andrew Lunn wrote: > Does Marvell mandate this PIC and gpio interface? Or is a board > designer free to implement it some other way? It seems to me, this > should be considered specific to the Marvell reference design. They don't mandate this interface, it's really a board-specific decision, which is why I've split my implementation between: * SoC-specific code, in mach-mvebu/pm.c. * Board-specific code, in mach-mvebu/pm-board.c. > I'm wondering if this code should be a power driver, living in > drivers/power/reset/. I'm fine with that, but have you seen the *very* tight interaction between the SoC-specific code and the board-specific code? The problem is that the board-specific code needs to put the SDRAM into self-refresh *right* before shutting down the SoC, and all that while making sure the code doing both of these operations remains in the I-Cache, and does not touch any other location in memory (which has become inaccessible due to being in self-refresh mode). Look at the mvebu_armada_xp_gp_pm_enter() function: it takes two arguments, received from the SoC-level code. How to handle this thing with a driver in drivers/power/reset/ ? > A few kirkwood boards have a PIC controlling the power. QNAP devices > use a serial port to talk to it. Others use a single gpio line. Is > there something to stop a designer doing this for XP? Nothing stops that. I think Marvell told me they wanted to standardize this GPIO interface with a PIC, but that's only for their own development boards. Since it remains something outside the SoC, it is by nature board-specific, and designers can do pretty much what they want. > It seems like you would have a more generic solution by allowing DT to > specify a power off driver to use. Sure, but see above. If you have some suggestion, I'm surely interested. Best regards, Thomas -- Thomas Petazzoni, CTO, Free Electrons Embedded Linux, Kernel and Android engineering http://free-electrons.com -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
