Hello, On Mon, Sep 11, 2017 at 08:47:03PM +0200, Enrico Weigelt, metux IT consult wrote: > On 11.09.2017 09:16, Uwe Kleine-König wrote: > > > Try adding a #define DEBUG in linux-4.13/arch/arm/boot/compressed/head.S > > > and make sure enabled DEBUG_LL and selected the right UART in your> > .config. > After deep digging in the init code, I've meanwhile fixed it (at least > with self-compiled 2015 bbx - didn't try newer versions yet). In the end > was just dt misconfiguration (that wasn't obvious in this dts wood, > which I ported from the old 4.1-phy tree): the debug uart was disabled. > > This lead to some funny situations: > > * DEBUG_ll worked after fixing the port number (the counting is a bit > confusing: ttymxc1 is #2) CONFIG_DEBUG_IMX_UART_PORT=2 means it should use UART-2 as documented in the reference manual. But yeah, this is confusing, the problem is that the hardware guy numbering the UARTS named the first UART UART-1 which isn't what a kernel hacker would have picked. > * console works up to the point where the uarts tty drivers are > configured. as the uart was disabled in dt, no tty driver was > associated (while ll driver was still active), so the clock was > disabled on some point, leading to supposedly hangup (actually, > just the console was gone) When the UART tty driver are configured doesn't play a role here. At some point during boot all unused clocks are disabled and up to then no driver ensured your uart clock to be used. And maybe you had a real hangup because writing to an UART with its clock off might have "funny" effects. > * hacking out the clock disable lead further to the point where rootfs > is mounted and init started There is no need for a hack, just pass "clk_ignore_unused" on the kernel command line. Best regards Uwe -- Pengutronix e.K. | Uwe Kleine-König | Industrial Linux Solutions | http://www.pengutronix.de/ | _______________________________________________ barebox mailing list barebox@xxxxxxxxxxxxxxxxxxx http://lists.infradead.org/mailman/listinfo/barebox
