[U-Boot] Linux seamless booting
Hi all, we've been working on a PPC512x board booting with u-boot + linux 2.6.24.6, and one major issue for our application is boot time.
Right now, we went down to less than 6s boot time (i.e. time from power off to launch of the user app), even with some drivers installed, i.e.:
* CAN bus * GPU on PCI bus * USB host * UBI
with r/o squashfs root and r/w ubifs configuration filesystem mounted from a NOR flash memory.
This time could be enough for the high-level application (we're showing a splash screen in about 2-3s so it's ok if the main app takes a little longer to come up), but the whole system is connected to others via CAN and we can't afford the "black out" period between u-boot and linux.
Some other operating systems (e.g. QNX) have this "seamless booting" function, in which drivers are started in stages, so that a (minimal) functionality can be given in milliseconds, and more functionalities come up as time goes by.
Is there a way to support something similar with the u-boot -> linux solution?
Thank you, Matteo
Did you try "setenv bootdelay 0" in uboot?
On Mon, Oct 12, 2009 at 7:07 AM, Fortini Matteo matteo.fortini@mta.it wrote:
Hi all, we've been working on a PPC512x board booting with u-boot + linux 2.6.24.6, and one major issue for our application is boot time.
Right now, we went down to less than 6s boot time (i.e. time from power off to launch of the user app), even with some drivers installed, i.e.:
* CAN bus * GPU on PCI bus * USB host * UBI
with r/o squashfs root and r/w ubifs configuration filesystem mounted from a NOR flash memory.
This time could be enough for the high-level application (we're showing a splash screen in about 2-3s so it's ok if the main app takes a little longer to come up), but the whole system is connected to others via CAN and we can't afford the "black out" period between u-boot and linux.
Some other operating systems (e.g. QNX) have this "seamless booting" function, in which drivers are started in stages, so that a (minimal) functionality can be given in milliseconds, and more functionalities come up as time goes by.
Is there a way to support something similar with the u-boot -> linux solution?
Thank you, Matteo _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev
Yes, that's what we're currently using, but the problem is a little broader: I should answer to CAN messages in at most 100-200ms from powerup, and that can be done in u-boot. However, handing CAN transmission control over to Linux is quite complicated nowadays, since it would involve passing structures in memory and hacking through device init. It'd be nice to have a framework with which u-boot could hand-over devices to Linux in a clean and defined way. We were thinking about starting some kind of development in that direction, but with very little resources, so I was looking for someone who had looked at the same problem.
Thanks, Matteo
Roberto Guerra ha scritto:
Did you try "setenv bootdelay 0" in uboot?
On Mon, Oct 12, 2009 at 7:07 AM, Fortini Matteo matteo.fortini@mta.it wrote:
Hi all, we've been working on a PPC512x board booting with u-boot + linux 2.6.24.6, and one major issue for our application is boot time.
Right now, we went down to less than 6s boot time (i.e. time from power off to launch of the user app), even with some drivers installed, i.e.:
- CAN bus
- GPU on PCI bus
- USB host
- UBI
with r/o squashfs root and r/w ubifs configuration filesystem mounted from a NOR flash memory.
This time could be enough for the high-level application (we're showing a splash screen in about 2-3s so it's ok if the main app takes a little longer to come up), but the whole system is connected to others via CAN and we can't afford the "black out" period between u-boot and linux.
Some other operating systems (e.g. QNX) have this "seamless booting" function, in which drivers are started in stages, so that a (minimal) functionality can be given in milliseconds, and more functionalities come up as time goes by.
Is there a way to support something similar with the u-boot -> linux solution?
Thank you, Matteo _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev
.
On Mon, 2009-10-12 at 15:54 +0200, Fortini Matteo wrote:
Yes, that's what we're currently using, but the problem is a little broader: I should answer to CAN messages in at most 100-200ms from powerup, and that can be done in u-boot.
if you are in that interval you definitely need to go to a more exotic start sequence than usual.
one solution would be to do as you suggest and do a special driver that is living outside of the kernel during startup. you still need to hack into the interrupt code to let your "external" driver handle the CAN. then you need to hack up the ordinary driver to take over from yours.
I have not seen this solution on any project I worked on but should be doable.
optimizing the boot time of linux so it starts up in 200ms is probably going to be quite hard. I did 2 seconds to /sbin/init started from ide driver without to much trouble. removing the IDE and going to a root on NOR would probably get closer to 1.5 but to get down to 200ms would probably mean removing most of u-boot and only keep the dram setup then you probably need to remove most of the drivers from the kernel and load them later as modules. I have never really tried to do a insane fast boot like this so I'm not sure what problems you will run up against. but maybe it's possible. but 200ms feels a bit to optimistic.
However, handing CAN transmission control over to Linux is quite complicated nowadays, since it would involve passing structures in memory and hacking through device init. It'd be nice to have a framework with which u-boot could hand-over devices to Linux in a clean and defined way.
not likely to happen as a generic solution. Much better to just remove the boat loader then and work on optimizing the linux startup code.
participants (3)
-
Fortini Matteo -
Kenneth Johansson -
Roberto Guerra