On Tue, 22 Mar 2016 00:02:57 +0100 Matthias Schiffer <mschiffer@xxxxxxxxxxxxxxxxxxxx> wrote: > Hi, > we're experiencing weird nondeterministic hangs during bootconsole/console > handover on some ath79 systems on OpenWrt. I've seen this issue myself on > kernel 3.18.23~3.18.27 on a AR7241-based system, but according to other > reports ([1], [2]) kernel 4.1.x is affected as well, and other SoCs like > QCA953x likewise. > > See the log below for the exact place it hangs; the log was taken in during > a good boot; a bad boot will just hang forever at the marked location. The > issue is extremely hard to debug, as changing the timing in any way (like > adding additional printk) will usually make it work without problems. (Even > recompiling the kernel with the same config, but different uname timestamp > will make the occurence more or less likely) > > My theory is the following: > > As soon as ttyS0 is detected and installed as the console, there are two > console drivers active on the serial port at the same time: early0 and > ttyS0. I suspect that the hang occurs when the primitive early0 > implementation prom_putchar_ar71xx waits indefinitely on THRE, Can you use EJTAG to prove your theory? -- Best regards, Antony Pavlov -- 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
