From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from mx1.redhat.com ([209.132.183.28]) by bombadil.infradead.org with esmtps (Exim 4.80.1 #2 (Red Hat Linux)) id 1YjFjU-0000p6-Hm for kexec@lists.infradead.org; Fri, 17 Apr 2015 23:31:37 +0000 Message-ID: <553197BE.7060705@redhat.com> Date: Sat, 18 Apr 2015 05:01:10 +0530 From: Pratyush Anand MIME-Version: 1.0 Subject: Re: [PATCH RFC 6/6] arm64: wait for transmit completion before next character transmission References: <6c8a63f701e98cb7cf4ddd96ab5b509115ebdc41.1429201849.git.panand@redhat.com> <1429291343.5479.22.camel@infradead.org> In-Reply-To: <1429291343.5479.22.camel@infradead.org> List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="us-ascii"; Format="flowed" Sender: "kexec" Errors-To: kexec-bounces+dwmw2=infradead.org@lists.infradead.org To: Geoff Levand Cc: kexec@lists.infradead.org, kexec@lists.fedoraproject.org On Friday 17 April 2015 10:52 PM, Geoff Levand wrote: > On Thu, 2015-04-16 at 22:17 +0530, Pratyush Anand wrote: >> Previous transmission must be completed before next character to be >> transmitted, otherwise TX buffer may saturate and we will not see all >> the characters on screen. >> >> @@ -34,6 +38,8 @@ static const char arm64_opts_usage[] __attribute__ ((unused)) = >> " --lite Fast reboot, no memory integrity checks.\n" >> " --page-offset Kernel page-offset for binary image load.\n" >> " --port=ADDRESS Purgatory output to port ADDRESS.\n" >> +" --port-lsr=ADDRESS Purgatory output port line status ADDRESS.\n" >> +" --port-lsr-val=VALUE Purgatory output port Line status expected SET value when TX empty.\n" >> " --ramdisk=FILE Use FILE as the kernel initial ramdisk.\n" >> " --reuse-cmdline Use command line arg of primary kernel.\n"; > > We just need to put some chars to the screen, so I want to avoid a lot > of parameters. > I was not able to get even two lines print without it :( > Usually the status register is at a fixed offset from the TX port. Is > that not the case for the ARM uarts? > > Can't we just poll port-lsr until empty then start writing again? That > will at least eliminate port-lsr-val. > infact my first version was using a direct offset with port. Both are fixed in most of the cases as offset 0x14 and value 0x60. OK, I will remove the param for now. if someone finds any different values then later on we can add it. ~Pratyush _______________________________________________ kexec mailing list kexec@lists.infradead.org http://lists.infradead.org/mailman/listinfo/kexec