Messages in this thread | | | Date | Mon, 30 Jan 2012 11:13:48 +0800 | From | Shawn Guo <> | Subject | Re: Pinmux bindings proposal V2 |
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On Fri, Jan 27, 2012 at 07:43:36AM -0800, Simon Glass wrote: ... > The cost of the pmx@dta node is about 12 bytes for the header (it > depends on the length of the name), and each of the properties above > is 16 bytes. So in total this node is 76 bytes. If we have 250 pins > being muxed as Tegra3 then this is about 20KB (including a bit of > slack for longer names). My point about being able to 'optimise out' > some of these remains, though, but probably not for the kernel. > > Stephen's 'mux' property uses 12 bytes plus 8 bytes per pin/group (I > am removing the prefixes): > > mux = > <PG_DTA MUX_SDIO1> > <PG_DTD MUX_SDIO1>; > > so 28 bytes. What I proposed would use (12 + 2 * 16) per pin/group, or > 44 bytes (60% bigger): > It's not only about size but also run-time tree travelling efficiency. Your proposal requires every single pin show as a node in device tree. Looking at these for_each_node_by_*() APIs in include/linux/of.h, you might agree we should avoid bloating device tree with so many nodes.
-- Regards, Shawn
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