Hi Sk, Please keep the Cc list intact (specifically U-Boot Users). Although some of these questions are a little off-topic for the list, there is much confusion about U-Boot as an embedded boot loader, CoreBoot as a BIOS replacement which can boot the Linux kernel directly and x86 'Bootloaders' such as LILO, GRUB etc. Having this information in the mailing list archive is important
On 25/08/10 17:58, sk ong wrote: > Graeme, > > Thanks for your response. > > I have not accessed gmail for few days, so I see this late, I will take > some time to digest and look at coreboot too. > > I do not fully understand, can I ask some questions? Sure - Questions are always welcome :) > > Board designer of embedded board knows the information, instead of BIOS, > how does u-boot pass this information to protected-mode entry of linux > kernel? The x86 Linux Kernel has two components, a 'Real-Mode' component (which has access to BIOS but very limited access to memory and devices) and a 'Protected-Mode' component (with no access to BIOS but full access to memory and devices). The 'Real-Mode' component of the Linux Kernel 'probes' BIOS (via BIOS interrupt calls) to build a list of fundamental information (primarily memory layout) in memory and invokes the 'Protected Mode' component passing a memory address of the information collected (from BIOS) in Real-Mode My intent is for U-Boot to replace the 'Real-Mode' component of Linux and build the necessary information and directly invoke the 'Protected Mode' component of the Linux Kernel (bypassing Real-Mode entirely). Because an embedded board designer designs all part of the system (RAM, ROM, device memory and interrupt maps etc), they can build this information without needing BIOS. > > Does uboot execute option rom, such as the option rom for PCI/PCIE video > controller, SATA controller, network controller, etc.? No (although you could write drivers to do so). I think U-Boot may already have drivers for common hardware already. Because of the GPL, any device supported by Linux can be ported to U-Boot be taking the existing Linux driver code (does need to be modified specifically for U-Boot, but all the hard work has already been done) > > What are the x86 CPU and board that can run uboot-x86? Currently U-Boot supports the AMD SC520 'Elan' embedded processor. I am about to port U-Boot to the VIA EPIA EN1200/1500 boards > > Is there a porting guide if I want to port uboot-x86 to another x86 board? > Unfortunately not > Can uboot-x86 boot x86 PC Linux like Fedora, Ubuntu, etc.? U-Boot cannot boot a PC. The VIA EPIA platform is marketed as 'Embedded' but it is (kind-of) a PC motherboard. PC's are very diverse - BIOS is intended to create an abstraction between the software and the hardware to some extent. To boot a PC, U-Boot would need to replace the BIOS and all the abstraction that entails which would, essentially, mimic coreboot (i.e. implementing such 'genericness' would be a complete waste of time) > > If uboot-x86 can boot x86 PC Linux, what stop it from booting Windows > (at least non-ACPI kernel WIndows)? U-Boot can boot other OS's. I think some have even booted Windows CE (the embedded version of windows) > > Without in13h in uboot-x86, how MBR/grub/lilo load Linux image from > storage such as SATA, SD, etc? Most embedded systems use Flash memory to store the filesystem. U-Boot has drivers to access file systems on MTD (Flash) devices. U-Boot also has a wide variety of driver to provide access to various storage devices (as well as network adapters, Serial ports, USB, video, PCMCIA etc) > > I am looking for uboot, not only for x86 PC, but also for other x86 > embedded OS. If you are booting a generic, off-the-shelf PC motherboard (Gigabyte, Tyan, Asus etc) then look at coreboot. If you are creating your own hardware design, use U-Boot > > Thanks, > SK > > > On Sat, Aug 21, 2010 at 9:42 AM, Graeme Russ <graeme.r...@gmail.com > <mailto:graeme.r...@gmail.com>> wrote: > > Hi SK, > > On 20/08/10 17:42, sk ong wrote: > > Hi, > > > > I notice there is u-boot for x86 architecture in the denx site. I > wonder > > whether the u-boot-x86 has the legacy BIOS services, such as > dispatching > > PCI/PCIE device option rom such as video, SATA, etc. Does it have > int13, > > int15 etc. services for x86 Linux to call during booting phase. > > The x86 port has an (extremely) limited BIOS primarily to provide > INT12 and > INT15 for the purpose of determining memory size during the Linux > Real-Mode > startup procedure. > > I don't think that Linux actually needs BIOS other than during the > initial > Real-Mode bootstrap. In an embedded environment, the board designer > knows > all the information the BIOS would otherwise provide. My goal is to > remove > the BIOS functionality from U-Boot and use the Protected-Mode entry > point > of the Linux kernel and avoid the switching back-and-forth between > Real and > Protected Modes > > It sounds like you might be looking at using U-Boot for booting a > x86 PC. > If this is the case, maybe you should take a look at coreboot > (http://www.coreboot.org/) > > Regards, > > Graeme > > _______________________________________________ U-Boot mailing list U-Boot@lists.denx.de http://lists.denx.de/mailman/listinfo/u-boot
