From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751932AbaL1SdU (ORCPT ); Sun, 28 Dec 2014 13:33:20 -0500 Received: from atrey.karlin.mff.cuni.cz ([195.113.26.193]:41583 "EHLO atrey.karlin.mff.cuni.cz" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751752AbaL1SdQ (ORCPT ); Sun, 28 Dec 2014 13:33:16 -0500 Date: Sun, 28 Dec 2014 19:33:07 +0100 From: Pavel Machek To: Joe Perches Cc: linux-arch , LKML , Geert Uytterhoeven , linux-m68k , Steven Miao , Ralf Baechle , linux-mips Subject: Re: rfc: remove early_printk from a few arches? (blackfin, m68k, mips) Message-ID: <20141228183306.GD3922@amd> References: <1418849927.28384.1.camel@perches.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1418849927.28384.1.camel@perches.com> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed 2014-12-17 12:58:47, Joe Perches wrote: > It seems like early_printk can be configured into > a few architectures but also appear not to be used. > > $ git grep -w "early_printk" > arch/arm/kernel/Makefile:obj-$(CONFIG_EARLY_PRINTK) += early_printk.o > arch/arm/kernel/early_printk.c: * linux/arch/arm/kernel/early_printk.c > arch/arm/mach-socfpga/socfpga.c: early_printk("Early printk initialized\n"); > arch/blackfin/kernel/Makefile:obj-$(CONFIG_EARLY_PRINTK) += early_printk.o > arch/blackfin/kernel/bfin_dma.c:#include > arch/blackfin/kernel/early_printk.c: * derived from arch/x86/kernel/early_printk.c > arch/blackfin/kernel/early_printk.c:#include > arch/blackfin/kernel/setup.c:#include > arch/blackfin/kernel/shadow_console.c:#include > arch/blackfin/mm/init.c:#include > arch/ia64/sn/kernel/setup.c: * IO on SN2 is done via SAL calls, early_printk won't work without this. > arch/m68k/kernel/Makefile:obj-$(CONFIG_EARLY_PRINTK) += early_printk.o > arch/microblaze/kernel/Makefile:obj-$(CONFIG_EARLY_PRINTK) += early_printk.o > arch/microblaze/kernel/cpu/cpuinfo-pvr-full.c: early_printk("ERROR: Microblaze " x "-different for PVR and DTS\n"); > arch/microblaze/kernel/cpu/cpuinfo-static.c: early_printk("ERROR: Microblaze " x "-different for kernel and DTS\n"); > arch/microblaze/kernel/setup.c:/* initialize device tree for usage in early_printk */ > arch/mips/ath25/Makefile:obj-$(CONFIG_EARLY_PRINTK) += early_printk.o > arch/mips/ath79/Makefile:obj-$(CONFIG_EARLY_PRINTK) += early_printk.o > arch/mips/bcm63xx/Makefile:obj-$(CONFIG_EARLY_PRINTK) += early_printk.o > arch/mips/include/asm/mach-lantiq/falcon/lantiq_soc.h: * during early_printk no ioremap possible at this early stage > arch/mips/include/asm/mach-lantiq/xway/lantiq_soc.h: * during early_printk no ioremap is possible > arch/mips/kernel/Makefile:obj-$(CONFIG_EARLY_PRINTK) += early_printk.o > arch/mips/lantiq/Makefile:obj-$(CONFIG_EARLY_PRINTK) += early_printk.o > arch/mips/loongson/common/Makefile:obj-$(CONFIG_EARLY_PRINTK) += early_printk.o > arch/mips/ralink/Makefile:obj-$(CONFIG_EARLY_PRINTK) += early_printk.o > arch/tile/kernel/Makefile:obj-$(CONFIG_EARLY_PRINTK) += early_printk.o > arch/tile/kernel/early_printk.c: early_printk("Kernel panic - not syncing: %pV", &vaf); > arch/um/kernel/Makefile:obj-$(CONFIG_EARLY_PRINTK) += early_printk.o > arch/unicore32/kernel/Makefile:obj-$(CONFIG_EARLY_PRINTK) += early_printk.o > arch/unicore32/kernel/early_printk.c: * linux/arch/unicore32/kernel/early_printk.c > arch/x86/kernel/Makefile:obj-$(CONFIG_EARLY_PRINTK) += early_printk.o > arch/x86/kernel/e820.c: early_printk(msg); > arch/x86/kernel/head64.c: early_printk("Kernel alive\n"); > arch/x86/kernel/head_64.S: call early_printk > arch/x86/platform/efi/Makefile:obj-$(CONFIG_EARLY_PRINTK_EFI) += early_printk.o > drivers/tty/serial/8250/8250_early.c: * and on early_printk.c by Andi Kleen. > drivers/tty/serial/sn_console.c: * synchronous (raw) and asynchronous (buffered). initially, early_printk > drivers/tty/serial/sn_console.c: /* without early_printk, we may be invoked late enough to race > drivers/tty/serial/sn_console.c: /* early_printk invocation may have done this for us */ > include/linux/printk.h:void early_printk(const char *fmt, ...); > include/linux/printk.h:void early_printk(const char *s, ...) { } > kernel/events/core.c: early_printk("perf interrupt took too long (%lld > %lld), lowering " > kernel/locking/lockdep.c: * We cannot printk in early bootup code. Not even early_printk() > kernel/printk/printk.c:asmlinkage __visible void early_printk(const char *fmt, ...) > kernel/printk/printk.c: * early_printk) - sometimes before setup_arch() completes - be careful > kernel/printk/printk.c: * There are two types of consoles - bootconsoles (early_printk) and > > These seem to the only uses: > > arch/arm/mach-socfpga/socfpga.c: early_printk("Early printk initialized\n"); > [] > arch/microblaze/kernel/cpu/cpuinfo-pvr-full.c: early_printk("ERROR: Microblaze " x "-different for PVR and DTS\n"); > arch/microblaze/kernel/cpu/cpuinfo-static.c: early_printk("ERROR: Microblaze " x "-different for kernel and DTS\n"); > [] > arch/tile/kernel/early_printk.c: early_printk("Kernel panic - not syncing: %pV", &vaf); > [] > arch/x86/kernel/e820.c: early_printk(msg); > arch/x86/kernel/head64.c: early_printk("Kernel alive\n"); > arch/x86/kernel/head_64.S: call early_printk > [] > kernel/events/core.c: early_printk("perf interrupt took too long (%lld > %lld), lowering " > > So blackfin, m68k, and mips seems to have it possible to enable, > but also don't appear at first glance to use it, > > Is early_printk really used by these architectures? > Should it be removed? early_printk() is for debugging. Actually, feel free to remove: arch/arm/mach-socfpga/socfpga.c: early_printk("Early printk initialized\n"); Its debugging output I added and should have been removed. So... early_printk()s _should_ be unused in the mainline code, but functionality should be kept, so that when someone needs it, he can enable it. Pavel -- (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html