Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752007AbcLFGei (ORCPT ); Tue, 6 Dec 2016 01:34:38 -0500 Received: from mx1.redhat.com ([209.132.183.28]:54508 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751779AbcLFGef (ORCPT ); Tue, 6 Dec 2016 01:34:35 -0500 Subject: Re: [PATCH] SPCR: check bit width for the 16550 UART To: Duc Dang References: <20161205130534.11080-1-aleksey.makarov@linaro.org> <3a6193ef-ca86-c113-b09a-5d6c882137e2@redhat.com> Cc: Aleksey Makarov , "Rafael J . Wysocki" , linux-acpi@vger.kernel.org, linux-serial@vger.kernel.org, Linux Kernel Mailing List , Greg Kroah-Hartman , Russell King , Peter Hurley , Mark Salter , Graeme Gregory , Len Brown From: Jon Masters Message-ID: <53421849-d031-77e1-9edb-53c9d673d462@redhat.com> Date: Tue, 6 Dec 2016 01:34:26 -0500 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.25]); Tue, 06 Dec 2016 06:34:34 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1547 Lines: 34 On 12/05/2016 10:55 PM, Duc Dang wrote: > On Mon, Dec 5, 2016 at 6:27 PM, Jon Masters wrote: >> Hi Duc, all, >> >> So after regenerating the initrd override (I must have fat fingered) >> it is now detecting the correct bit width on boot (attached dmesg log). >> >> HOWEVER while the console does come up, the use of "earlycon" on the >> command line (with no parameters) doesn't result in the early SPCR >> console coming up correctly. I see some garbled characters that >> suggest the baud (or register access width) is off somewhere. > > My bad that I did not catch this in the morning. Yes, earlycon does > not seems to work as expected. I can see that earlycon parameters > seems to be correct, but the bootconsole message does not come out > (the following is from 'dmesg') > [ 0.000000] ACPI: SPCR: console: uart,mmio32,0x1c020000,115200 > [ 0.000000] earlycon: uart0 at MMIO32 0x000000001c020000 (options '115200') > [ 0.000000] bootconsole [uart0] enabled The difference appears to be in the baud rate. When I explicitly specify "earlycon=uart8250,mmio32,0x1c021000" no baud is set. When booting with the SPCR, the baud is set to 9600 in my case or 115200 in yours. But we both know that the base clock on the X-Gene UART is weird. Maybe somehow we can explain this through the lack of setting a baud. I am pondering some more currently. If it's X-Gene specific, let's add that to the quirk (and to perhaps a more APM specific SPCR subtype). Jon. -- Computer Architect | Sent from my Fedora powered laptop