From mboxrd@z Thu Jan 1 00:00:00 1970 From: Domen Puncer Date: Wed, 18 Apr 2007 07:55:07 +0200 Subject: [U-Boot-Users] [PATCH] icecube/lite5200b: document wakeup from low-power support In-Reply-To: <20070417145019.AFA8B352658@atlas.denx.de> References: <200704171329.37002.sr@denx.de> <20070417145019.AFA8B352658@atlas.denx.de> Message-ID: <20070418055507.GA27576@nd47.coderock.org> List-Id: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: u-boot@lists.denx.de Document what Lite5200B low-power is about. Signed-off-by: Domen Puncer --- doc/README.Lite5200B_low_power | 22 ++++++++++++++++++++++ 1 file changed, 22 insertions(+) Index: u-boot.git/doc/README.Lite5200B_low_power =================================================================== --- /dev/null +++ u-boot.git/doc/README.Lite5200B_low_power @@ -0,0 +1,22 @@ +Lite5200B wakeup from low-power mode (CONFIG_LITE5200B_PM) +---------------------------------------------------------- + +Low-power mode as described in Lite5200B User's Manual, means that +with support of MC68HLC908QT1 microcontroller (refered to as QT), +everything but the SDRAM can be powered down. This brings +maximum power saving, while one can still restore previous state +quickly. + +Quick overview where U-Boot comes into the picture: +- OS saves device states +- OS saves wakeup handler address to physical 0x0, puts SDRAM into + self-refresh and signals to QT, it should power down the board +- / board is sleeping here / +- someone presses SW4 (connected to QT) +- U-Boot checks PSC2_4 pin, if QT drives it down, then we woke up, + so get SDRAM out of self-refresh and transfer control to OS + wakeup handler +- OS restores device states + +This was tested on Linux with USB and Ethernet in use. Adding +support for other devices is an OS issue.