From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751212Ab3EUEHo (ORCPT ); Tue, 21 May 2013 00:07:44 -0400 Received: from intranet.asianux.com ([58.214.24.6]:29521 "EHLO intranet.asianux.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750715Ab3EUEHn (ORCPT ); Tue, 21 May 2013 00:07:43 -0400 X-Spam-Score: -100.8 Message-ID: <519AF2DC.2040200@asianux.com> Date: Tue, 21 May 2013 12:06:52 +0800 From: Chen Gang User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130110 Thunderbird/17.0.2 MIME-Version: 1.0 To: Will Deacon CC: Marc Zyngier , Catalin Marinas , Santosh Shilimkar , Tony Lindgren , "linux-arm-kernel@lists.infradead.org" , "linux-kernel@vger.kernel.org" Subject: Re: [PATCH] arm64: kernel: compiling issue, need 'EXPORT_SYMBOL_GPL(read_current_timer)' References: <5199C725.8050102@asianux.com> <168084c28e8ba5124c05553e97463172@localhost> <20130520095606.GH31359@mudshark.cambridge.arm.com> In-Reply-To: <20130520095606.GH31359@mudshark.cambridge.arm.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 05/20/2013 05:56 PM, Will Deacon wrote: > On Mon, May 20, 2013 at 08:15:04AM +0100, Marc Zyngier wrote: >> On Mon, 20 May 2013 14:48:05 +0800, Chen Gang >> wrote: >>> Need 'EXPORT_SYMBOL_GPL(read_current_timer)' if build with allmodconfig. >>> >>> The related error: >>> ERROR: "read_current_timer" [lib/rbtree_test.ko] undefined! >>> ERROR: "read_current_timer" [lib/interval_tree_test.ko] undefined! >>> ERROR: "read_current_timer" [fs/ext4/ext4.ko] undefined! >>> ERROR: "read_current_timer" [crypto/tcrypt.ko] undefined! >>> >>> >>> Signed-off-by: Chen Gang >>> --- >>> arch/arm64/kernel/time.c | 1 + >>> 1 files changed, 1 insertions(+), 0 deletions(-) >>> >>> diff --git a/arch/arm64/kernel/time.c b/arch/arm64/kernel/time.c >>> index a551f88..7fcba80 100644 >>> --- a/arch/arm64/kernel/time.c >>> +++ b/arch/arm64/kernel/time.c >>> @@ -73,6 +73,7 @@ int read_current_timer(unsigned long *timer_value) >>> *timer_value = arch_timer_read_counter(); >>> return 0; >>> } >>> +EXPORT_SYMBOL_GPL(read_current_timer); >>> >>> void __init time_init(void) >>> { >> >> While this solves the problem, I'm not sure this is the best fix. The real >> issue is with get_cycles, which is a macro around read_current_timer. >> >> AArch32 exports it because of the number of timer implementations. On >> arm64, we should be able to just return CNTVCT_EL0. >> >> Catalin, Will, what do you think? > > Should be ok once the arch timer driver has moved exclusively to virtual > time. I'm also not sure we even need to implement read_current_timer() -- > it's only used for delay-loop calibration, which we don't need for the > arch timer. > For whether we need implement read_current_timer(): many platforms have implemented it (openrisc, arm, sparc, hexagon, avr32, x86). it is called by init/calibrate.c when 'ARCH_HAS_READ_CURRENT_TIMER' is defined. since arm64 can implement it, better to provide it as an architect features to let outside use. For the implementation of read_current_timer(): it has to face various configurations (e.g. CONFIG_ARM_ARCH_TIMER, arch_timer_read_zero, arch_counter_get_cntvct, arch_counter_get_cntpct) so better still use variable instead of. (excuse me, I do not know what is 'CNTVCT_EL0', is it like a constant number ?) For the implementation of get_cycles() if read_current_timer() is provided, better to let get_cycles() to call it, instead of implement once again. Thanks. -- Chen Gang Asianux Corporation