Messages in this thread | | | Date | Fri, 29 Aug 2014 09:56:45 -0600 | From | Stephen Warren <> | Subject | Re: [PATCH] earlyprintk: re-enable earlyprintk calling early_param |
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On 08/28/2014 11:28 PM, Sahara wrote: > > > On Wed, 27 Aug 2014, Thierry Reding wrote: > >> On Thu, Aug 14, 2014 at 07:13:36PM +0900, kpark3469@gmail.com wrote: >>> From: Sahara <keun-o.park@windriver.com> >>> >>> Although there are many obs_kernel_param and its names are >>> earlyprintk and also EARLY_PRINTK is also enabled, we could not >>> see the early_printk output properly until now. This patch >>> considers earlycon as well as earlyprintk. >>> >>> Signed-off-by: Sahara <keun-o.park@windriver.com> >>> --- >>> init/main.c | 3 ++- >>> 1 file changed, 2 insertions(+), 1 deletion(-) >>> >>> diff --git a/init/main.c b/init/main.c >>> index bb1aed9..235d248 100644 >>> --- a/init/main.c >>> +++ b/init/main.c >>> @@ -426,7 +426,8 @@ static int __init do_early_param(char *param, char > *val, const char *unused) >>> for (p = __setup_start; p < __setup_end; p++) { >>> if ((p->early && parameq(param, p->str)) || >>> (strcmp(param, "console") == 0 && >>> - strcmp(p->str, "earlycon") == 0) >>> + ((strcmp(p->str, "earlycon") == 0) || >>> + (strcmp(p->str, "earlyprintk") == 0))) >>> ) { >>> if (p->setup_func(val) != 0) >>> pr_warn("Malformed early option '%s'\n", > param); >> >> It seems like this patch causes the following warning for me during >> boot: >> >> [ 0.000000] Booting Linux on physical CPU 0x0 >> [ 0.000000] Initializing cgroup subsys cpu >> [ 0.000000] Initializing cgroup subsys cpuacct >> [ 0.000000] Linux version 3.17.0-rc2-next-20140827 > (thierry.reding@ulmo) (gcc version 4.9.0 (GCC) ) #18 SMP PREEMPT Wed Aug > 27 17:08:12 CEST 2014 >> [ 0.000000] CPU: ARMv7 Processor [413fc0f3] revision 3 (ARMv7), > cr=10c5387d >> [ 0.000000] CPU: PIPT / VIPT nonaliasing data cache, PIPT instruction > cache >> [ 0.000000] Machine model: NVIDIA Tegra124 Jetson TK1 >> [ 0.000000] bootconsole [earlycon0] enabled >> [ 0.000000] debug: ignoring loglevel setting. >> [ 0.000000] ------------[ cut here ]------------ >> [ 0.000000] WARNING: CPU: 0 PID: 0 at > /home/thierry.reding/src/kernel/linux-work.git/kernel/printk/printk.c:2402 > register_console+0x60/0x37c() >> [ 0.000000] console 'earlycon0' already registered >> [ 0.000000] Modules linked in: >> [ 0.000000] CPU: 0 PID: 0 Comm: swapper Not tainted > 3.17.0-rc2-next-20140827 #18 >> [ 0.000000] [<c0015fec>] (unwind_backtrace) from [<c0011aac>] > (show_stack+0x10/0x14) >> [ 0.000000] [<c0011aac>] (show_stack) from [<c062b700>] > (dump_stack+0x98/0xd8) >> [ 0.000000] [<c062b700>] (dump_stack) from [<c0025ba0>] > (warn_slowpath_common+0x70/0x8c) >> [ 0.000000] [<c0025ba0>] (warn_slowpath_common) from [<c0025bec>] > (warn_slowpath_fmt+0x30/0x40) >> [ 0.000000] [<c0025bec>] (warn_slowpath_fmt) from [<c00639b8>] > (register_console+0x60/0x37c) >> [ 0.000000] [<c00639b8>] (register_console) from [<c0883870>] > (setup_early_printk+0x20/0x28) >> [ 0.000000] [<c0883870>] (setup_early_printk) from [<c087f43c>] > (do_early_param+0x6c/0xd0) >> [ 0.000000] [<c087f43c>] (do_early_param) from [<c003cba0>] > (parse_args+0x238/0x3d0) >> [ 0.000000] [<c003cba0>] (parse_args) from [<c087f814>] > (parse_early_options+0x38/0x40) >> [ 0.000000] [<c087f814>] (parse_early_options) from [<c087f84c>] > (parse_early_param+0x30/0x40) >> [ 0.000000] [<c087f84c>] (parse_early_param) from [<c088206c>] > (setup_arch+0x4b4/0x974) >> [ 0.000000] [<c088206c>] (setup_arch) from [<c087f8f8>] > (start_kernel+0x98/0x3a8) >> [ 0.000000] [<c087f8f8>] (start_kernel) from [<80008074>] > (0x80008074) >> [ 0.000000] ---[ end trace cb88537fdc8fa200 ]--- >> [ 0.000000] cma: Reserved 128 MiB at a7800000 >> [ 0.000000] Memory policy: Data cache writealloc >> [ 0.000000] On node 0 totalpages: 524032 >> [ 0.000000] free_area_init_node: node 0, pgdat c091cc00, node_mem_map > e67b7000 >> [ 0.000000] Normal zone: 1520 pages used for memmap >> [ 0.000000] Normal zone: 0 pages reserved >> [ 0.000000] Normal zone: 194560 pages, LIFO batch:31 >> [ 0.000000] HighMem zone: 2574 pages used for memmap >> [ 0.000000] HighMem zone: 329472 pages, LIFO batch:31 >> [ 0.000000] PERCPU: Embedded 8 pages/cpu @e6767000 s8832 r8192 d15744 > u32768 >> [ 0.000000] pcpu-alloc: s8832 r8192 d15744 u32768 alloc=8*4096 >> [ 0.000000] pcpu-alloc: [0] 0 [0] 1 [0] 2 [0] 3 >> [ 0.000000] Built 1 zonelists in Zone order, mobility grouping on. > Total pages: 522512 >> [ 0.000000] Kernel command line: console=ttyS0,115200n8 > ignore_loglevel rootwait ro earlyprintk ip=:::::eth0:dhcp root=/dev/nfs > nfsroot=192.168.69.100:/srv/nfs/tegra124 drm.debug=0xf cma=128M >> >> Reverting the patch eliminates the warning. earlyprintk does work fine >> for me without this patch. >> >> Thierry > > > This warning message is caused by specifying 'earlyprintk' in > your command line args. Same problem may happen if you specify 'earlycon' > in your command line args and enable CONFIG_SERIAL_EARLYCON with > the current code without this patch. I think it's appropriate result > letting a developer know that both ways of using earlyprintk are enabled. > With current code, although a developer enables CONFIG_EARLY_PRINTK and > has "console=" arg in command line args, he/she should specify the > 'earlyprintk' in command line args also to see early_printk() outputs. > With this patch, simply enabling CONFIG_EARLY_PRINTK and having 'console=' > line make you be able to the early_printk(). > > Nonetheless I want to retract this patch. It's good for ARM, but not good > for other architectures such as x86. And, because CONFIG_EARLY_PRINTK is > depending on DEBUG_LL in ARM, making a relation with "console=" is absurd. > (see strcmp(param, "console") == 0 && strcmp(p->str, "earlyprintk") == 0)
Even on ARM, this patch feels like the wrong thing. After all, I can build a DEBUG_LL enabled multi-platform kernel, and boot it on a bunch of different SoCs. However, earlyprintk will only work on one (or zero) of those SoCs, and hence shouldn't automatically enable itself; specifically requesting activation using the earlyprintk kernel command-line parameter is the correct approach.
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