Hi Simon, On Wed, Mar 21, 2012 at 10:33 AM, Simon Glass <s...@chromium.org> wrote: > 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.
But I don't get it - In your Seaboard patch, you only use UARTD so in this case we could CONFIG_ it? And it's sounding like for other scenarios you are going to resign yourself to there not being a common UART so you will send the pre-console (panic) message to multiple UARTs - something that should be avoided at all costs... I know we are dealing with a corner case abnormal situation here, but something does not smell right... Maybe I'm not understanding something obvious yet... Regards, Graeme _______________________________________________ U-Boot mailing list U-Boot@lists.denx.de http://lists.denx.de/mailman/listinfo/u-boot
