1 From eadd32681787b1828ff92ef5046db6568d52ad55 Mon Sep 17 00:00:00 2001
2 From: Phil Elwell <phil@raspberrypi.org>
3 Date: Tue, 29 May 2018 10:52:11 +0100
4 Subject: [PATCH 308/454] overlays: Add sdtweak features for network booting
6 It has been observed that a Pi with no SD card will poll the interface
7 continuously, using up to 10% CPU. Add some new parameters to the
8 sdtweak overlay to control this behaviour:
10 poll_once Only look for a card once, at boot time. If none is found
11 then the interface is effectively disabled.
13 enable Set to "off" or "no" to completely disable the interface.
15 See: https://github.com/raspberrypi/linux/issues/2567
17 Signed-off-by: Phil Elwell <phil@raspberrypi.org>
19 arch/arm/boot/dts/overlays/README | 10 ++++++++++
20 arch/arm/boot/dts/overlays/sdtweak-overlay.dts | 2 ++
21 2 files changed, 12 insertions(+)
23 --- a/arch/arm/boot/dts/overlays/README
24 +++ b/arch/arm/boot/dts/overlays/README
25 @@ -1618,6 +1618,16 @@ Params: overclock_50 Clock (i
27 debug Enable debug output (default off)
29 + poll_once Looks for a card once after booting. Useful
30 + for network booting scenarios to avoid the
31 + overhead of continuous polling. N.B. Using
32 + this option restricts the system to using a
33 + single card per boot (or none at all).
36 + enable Set to off to completely disable the interface
41 Info: Enables the Secondary Memory Interface peripheral. Uses GPIOs 2-25!
42 --- a/arch/arm/boot/dts/overlays/sdtweak-overlay.dts
43 +++ b/arch/arm/boot/dts/overlays/sdtweak-overlay.dts
45 force_pio = <&frag0>,"brcm,force-pio?";
46 pio_limit = <&frag0>,"brcm,pio-limit:0";
47 debug = <&frag0>,"brcm,debug?";
48 + enable = <&frag0>,"status";
49 + poll_once = <&frag0>,"non-removable?";