Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S967966Ab3DSJ20 (ORCPT ); Fri, 19 Apr 2013 05:28:26 -0400 Received: from cam-admin0.cambridge.arm.com ([217.140.96.50]:60785 "EHLO cam-admin0.cambridge.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S967926Ab3DSJ2Z (ORCPT ); Fri, 19 Apr 2013 05:28:25 -0400 Date: Fri, 19 Apr 2013 10:27:52 +0100 From: Will Deacon To: Pranavkumar Sawargaonkar Cc: Marc Zyngier , "linaro-kernel@lists.linaro.org" , Anup Patel , Patch Tracking , Rusty Russell , "linux-kernel@vger.kernel.org" , "kvmarm@lists.cs.columbia.edu" , "linux-arm-kernel@lists.infradead.org" Subject: Re: [RFC] arm64: Early printk support for virtio-mmio console devices. Message-ID: <20130419092752.GB13283@mudshark.cambridge.arm.com> References: <1366264344-28025-1-git-send-email-pranavkumar@linaro.org> <20130419090558.GA13283@mudshark.cambridge.arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1543 Lines: 31 On Fri, Apr 19, 2013 at 10:25:35AM +0100, Pranavkumar Sawargaonkar wrote: > On 19 April 2013 14:35, Will Deacon wrote: > > On Thu, Apr 18, 2013 at 09:48:49AM +0100, Pranavkumar Sawargaonkar wrote: > >> Actually i thought adding a config register will be easier to add a > >> code than writing entire emulation as 8250 emulation will require to > >> deal with dealing with more registers and more code. > > > > kvmtool already has an 8250 emulation! All we need to do is hack together > > something which will allow us to instantiate those ioport devices in a more > > flexible manner (namely, inside the MMIO space for ARM). For earlyprintk, I > > suspect we can get away without an interrupt too, which should simplify > > things a bit to start with. > > > > Regardless of the outcome of this discussion, I think getting the 8250 > > working on ARM is definitely something worth doing. If I get time, I'll take > > a look. > > I am not against using 8250 emulation (as far as it solves printk > issues for kernel booting logs), but my point is why not to add early > read-write support for virtio console, which also can be useful in > emulation less mach-virt environment also ? We can have both, but only one of those requires a change to the virtio specification. Will -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/