Commit a2a82c74 authored by Phil Elwell's avatar Phil Elwell
Browse files

overlays: Add sdtweak features for network booting 

It has been observed that a Pi with no SD card will poll the interface
continuously, using up to 10% CPU. Add some new parameters to the
sdtweak overlay to control this behaviour:

poll_once   Only look for a card once, at boot time. If none is found
            then the interface is effectively disabled.

enable      Set to "off" or "no" to completely disable the interface.

See: https://github.com/raspberrypi/linux/issues/2567



Signed-off-by: default avatarPhil Elwell <phil@raspberrypi.org>
parent a2092141

arch/arm/boot/dts/overlays/README

+10 −0
Original line number Diff line number Diff line
@@ -1618,6 +1618,16 @@ Params: overclock_50 Clock (in MHz) to use when the MMC framework 


        debug                   Enable debug output (default off)



        poll_once               Looks for a card once after booting. Useful

                                for network booting scenarios to avoid the

                                overhead of continuous polling. N.B. Using

                                this option restricts the system to using a

                                single card per boot (or none at all).

                                (default off)



        enable                  Set to off to completely disable the interface

                                (default on)





Name:   smi

Info:   Enables the Secondary Memory Interface peripheral. Uses GPIOs 2-25!

arch/arm/boot/dts/overlays/sdtweak-overlay.dts

+2 −0
Original line number Diff line number Diff line
@@ -19,5 +19,7 @@ 
		force_pio        = <&frag0>,"brcm,force-pio?";

		pio_limit        = <&frag0>,"brcm,pio-limit:0";

		debug            = <&frag0>,"brcm,debug?";

		enable           = <&frag0>,"status";

		poll_once        = <&frag0>,"non-removable?";

	};

};