On Wed, 2018-02-21 at 11:00 +0100, Maxime Ripard wrote:
> Hi David,
>
> On Sat, Feb 03, 2018 at 10:14:31AM +0100, Maxime Ripard wrote:
> >
> > From: Heiko Stuebner <heiko.stuebner@xxxxxx>
> >
> > On i.MX, which carries a lot of pin-groups of which most are unused on
> > individual boards, they noticed that this plethora of nodes also results
> > in the runtime-lookup-performance also degrading [0].
> >
> > A i.MX-specific solution defining the pingroups in the board files but
> > using macros to reference the pingroup-data was not well received.
> >
> > This patch is trying to solve this issue in a more general way, by
> > adding the ability to mark nodes as needing to be referenced somewhere
> > in the tree.
> >
> > To mark a node a needing to be referenced it must be prefixed with
> > /delete-if-unreferenced/. This makes dtc check the nodes reference-status
> > when creating the flattened tree, dropping it if unreferenced.
> >
> > For example, the i.MX6SL pingroup
> >
> > /delete-if-unreferenced/ pinctrl_ecspi1_1: ecspi1grp-1 {
> > fsl,pins = <
> > MX6SL_PAD_ECSPI1_MISO__ECSPI1_MISO 0x100b1
> > MX6SL_PAD_ECSPI1_MOSI__ECSPI1_MOSI 0x100b1
> > MX6SL_PAD_ECSPI1_SCLK__ECSPI1_SCLK 0x100b1
> > >;
> > };
> >
> > would only be included in the dtb if it got referenced somewhere
> > as pingroup via
> >
> > node {
> > pinctrl-0 <&pinctrl_ecscpi1_1>;
> > };
> >
> > [0] http://thread.gmane.org/gmane.linux.ports.arm.kernel/275912/
> Have you been able to take a look at this?
Wouldn't this destroy the ability to use overlays, whose whole point is
to establish references at runtime rather than compile time?
-- Ian
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