Hi Graeme, On Tue, Mar 20, 2012 at 4:28 PM, Graeme Russ <graeme.r...@gmail.com> wrote: > Hi Stephen, Simon, > > On Wed, Mar 21, 2012 at 8:17 AM, Stephen Warren <swar...@wwwdotorg.org> wrote: >> On 03/20/2012 02:13 PM, Simon Glass wrote: >>> Hi Stephen, >>> >>> On Tue, Mar 20, 2012 at 12:57 PM, Stephen Warren <swar...@wwwdotorg.org> >>> wrote: >>>> This works together with a kernel change that looks at the scratchpad >>>> register to determine which of the many UARTs it should use for early >>>> printing: >>>> >>>> http://www.spinics.net/lists/arm-kernel/msg154633.html >>>> >>>> Note that this configuration only affects the kernel's decompressor and >>>> earlyprintk code. Once the kernel is initialized far enough to parse the >>>> device tree, the console is initialized using information contained >>>> therein. >>>> >>>> Base on work by Doug Anderson <diand...@chromium.org>, but significantly >>>> rewritten. >>>> >>>> Signed-off-by: Stephen Warren <swar...@wwwdotorg.org> > >> >>> For the pre-console panic stuff, the point is that there may well be >>> one UART used for the console, but *we don't know which one it is!*. >> >> That's where we disagree. >> >> For each board, there is a single fixed UART that should be used for >> both pre-console panic and the "real" console later. This is fixed by >> the single static board design. > > I agree - The board designer should specify a 'default' debug port which > is used for all character output prior to the 'configured' console port > being initialised.
We can provide that, but if it is wrong for the board we are using, then there will be no output. Stephen's original complaint was a brick if there is no valid device tree. We need this to work! > > In the 'normal' boot case, the default console should never have any output > sent to it (unless it also happens to be the 'configured' console port) as > Both U-Boot and Linux will use a pre console buffer to buffer any output > prior to the 'configured' console being available > > So I think there is a clear evidence that the 'Board panic no console' > and 'Specify debugging serial port at boot' are intrinsicly related - Both > U-Boot and Linux should be dumping their 'pre-console' messages to the > same port and this port should be specified by the hardware designer > > So that being the case, there should be a single CONFIG_ option which > both patches should be using We cannot select the UART via CONFIG - remember that all of these boards have the same U-Boot binary. Please read that again :-) The device tree is the only thing that distinguishes them. All of the CONFIG options are identical for all boards. If I had time right now I would send out a proper serial fdt patch series - the previous one was just a WIP. But you can see it here: https://gerrit.chromium.org/gerrit/#change,18257 > > Just my 2% of $1.00 ;) > > Regards, > > Graeme Regards, Simon _______________________________________________ U-Boot mailing list U-Boot@lists.denx.de http://lists.denx.de/mailman/listinfo/u-boot
