Hi! I got a strange effect when using the auxiliar UART as the logging console: The kernel is configured for drivers/tty/serial/8250/8250_bcm2835aux.c to get linked into the main kernel (requires also 8250.c to be linked in). As long as I boot using the main UART (PL011) in the kernel parameters: earlyprintk consoleblank=0 console=ttyAMA0 root=/dev/mmcblk0p2 rootwait Everything works fine - early_printk works and normal logging works as well. Both configured ttys (/dev/ttyAMA0 and /dev/ttyS0) in /etc/initttab work fine. Now when I switch the console to use the auxiliar UART (which right now does not support early_printk) like this: earlyprintk consoleblank=0 console=ttyS0,115200n1 root=/dev/mmcblk0p2 rootwait I get the situation where: * u-boot starts and writes to the main UART * Kernel boots using early_printk logging to the main UART until we get to: [ 2.657090] bootconsole [earlycon0] disabled * then we see the earlyprintk buffer dumped on the aux-uart * then booting continues and logging happens on the aux-uart: [ 2.657090] bootconsole [earlycon0] disabled [ 2.662673] 20201000.serial: ttyAMA0 at MMIO 0x20201000 (irq = 81, base_baud = 0) is a PL011 rev2 [ 2.663793] console [ttyS0] disabled [ 2.663899] 20215040.serial: ttyS0 at MMIO 0x0 (irq = 53, base_baud = 31224999) is a 16550 [ 3.384166] console [ttyS0] enabled * everything works fine and I get networking and everything up [....] Starting NTP server: ntpd. ok [....] Starting OpenBSD Secure Shell server: sshd. ok My IP address is 10.10.10.41 ::127.0.0.1 Raspbian GNU/Linux 7 raspcm.intern.sperl.org ttyS0 * I can even log in via SSH and networking works. Note that I have the getty for ttyAMA0 disabled in inittab * when I then enable the tty on the main UART like this: root@raspcm:~# /sbin/getty -a root -L ttyAMA0 115200 vt100 * I get the following: [ 72.962845] uart-pl011 20201000.serial: no DMA platform data * the system freezes… * sometimes I still get the following on the auxiliar UART before the system “crashes": (at least when starting the tty from inittab) [ 73.072985] bcm2835-clk 20101000.cprman: plld: couldn't lock PLL [ 73.079132] ------------[ cut here ]------------ [ 73.083848] WARNING: CPU: 0 PID: 2329 at drivers/clk/clk.c:680 clk_core_disable+0x34/0xf0() [ 73.093067] ---[ end trace 416e78cea88f5fb5 ]--- [ 73.097848] ------------[ cut here ]------------ [ 73.102616] WARNING: CPU: 0 PID: 2329 at drivers/clk/clk.c:575 clk_core_unprepare+0x34/0x110() [ 73.112219] ---[ end trace 416e78cea88f5fb6 ]--- A similar effect I get when using stty: root@raspcm:~# stty -F /dev/ttyAMA0 [ 128.878127] uart-pl011 20201000.serial: no DMA platform data speed 9600 baud; line = 0; -brkint -imaxbel Then the system freezes. As if the plld does not lock - even if it (probably) is already locked. Or the message actually comes from bcm2835_clock_wait_busy which also produces this message - so maybe we should better identify the message. Note that the same also applies if I remove earlyprintk with the only difference being that I do not get the initial boot messages on the main UART. (at that time only: "Uncompressing Linux... done, booting the kernel.” shows on the main uart after u-boot start..) Unfortunately it is only possible to really test this on a rpi-Compute module, as only there we can expose both uarts on distinct GPIOs at the same time: GPIO 14: level=1 fsel=4 alt=0 func=TXD0 GPIO 15: level=1 fsel=4 alt=0 func=RXD0 GPIO 32: level=1 fsel=2 alt=5 func=TXD1 GPIO 33: level=1 fsel=2 alt=5 func=RXD1 Here the commits I have used based on spi/for-next (based on 4.4.0) with the patches (* prefix) for the driver for aux-uart added separately as they are not in the tree I have used: * a96f6c7 serial: bcm2835: add driver for bcm2835-aux-uart * 464e876 clk: bcm2835: Add bindings for the auxiliary peripheral clock gates. * 1af1b28 clk: bcm2835: Add a driver for the auxiliary peripheral clock gates. ece19b8 Merge remote-tracking branch 'spi/fix/loopback' into spi-linus 887e6a3 Merge tag 'spi-v4.5' into spi-linus ebea7c0 spi: fix counting in spi-loopback-test code cabeea9 Merge remote-tracking branches 'spi/topic/sun4i', 'spi/topic/topcliff-pc 4f95307 Merge remote-tracking branches 'spi/topic/overlay', 'spi/topic/pxa2xx', 41d5a70 Merge remote-tracking branches 'spi/topic/lm70llp', 'spi/topic/loopback' 635b9b2 Merge remote-tracking branches 'spi/topic/dw', 'spi/topic/dw-mid', 'spi/ 3c27892 Merge remote-tracking branches 'spi/topic/bcm63xx', 'spi/topic/butterfly 9b17e80 Merge remote-tracking branch 'spi/topic/sunxi' into spi-next 174c211 Merge remote-tracking branch 'spi/topic/core' into spi-next f30f072 Merge remote-tracking branch 'spi/fix/mtk' into spi-linus afd2ff9 Linux 4.4 Maybe someone has gotten any idea? In the meantime I will try to reproduce on a 4.5-rc3 based branch. Thanks, Martin -- To unsubscribe from this list: send the line "unsubscribe linux-serial" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
