From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Message-ID: <1429291343.5479.22.camel@infradead.org> Subject: Re: [PATCH RFC 6/6] arm64: wait for transmit completion before next character transmission From: Geoff Levand Date: Fri, 17 Apr 2015 10:22:23 -0700 In-Reply-To: <6c8a63f701e98cb7cf4ddd96ab5b509115ebdc41.1429201849.git.panand@redhat.com> References: <6c8a63f701e98cb7cf4ddd96ab5b509115ebdc41.1429201849.git.panand@redhat.com> Mime-Version: 1.0 List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "kexec" Errors-To: kexec-bounces+dwmw2=infradead.org@lists.infradead.org To: Pratyush Anand Cc: kexec@lists.infradead.org, kexec@lists.fedoraproject.org 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. 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. -Geoff _______________________________________________ kexec mailing list kexec@lists.infradead.org http://lists.infradead.org/mailman/listinfo/kexec