Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752970AbcLFADf (ORCPT ); Mon, 5 Dec 2016 19:03:35 -0500 Received: from mx1.redhat.com ([209.132.183.28]:44636 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752109AbcLFADc (ORCPT ); Mon, 5 Dec 2016 19:03:32 -0500 Subject: Re: [PATCH] SPCR: check bit width for the 16550 UART To: Duc Dang References: <20161205130534.11080-1-aleksey.makarov@linaro.org> 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: <0ac8dc36-38d9-0f08-9f5f-021f40b8ea7d@redhat.com> Date: Mon, 5 Dec 2016 19:03:25 -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 [10.5.110.28]); Tue, 06 Dec 2016 00:03:31 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1611 Lines: 42 On 12/05/2016 06:52 PM, Duc Dang wrote: > Hi Jon, > > On Mon, Dec 5, 2016 at 3:27 PM, Jon Masters wrote: >> Duc, Aleksey, all, >> >> I have a question about this... >> >> On 12/05/2016 01:51 PM, Duc Dang wrote: >>> On Mon, Dec 5, 2016 at 5:05 AM, Aleksey Makarov >>> wrote: >>>> Check the 'Register Bit Width' field of the ACPI Generic Address >>>> Structure that specifies the address of the UART registers to >>>> decide if the driver should use "mmio32" access instead of "mmio". >>>> >>>> If the driver is other than 16550 the access with is defined >>>> by the Interface Type field of the SPCR table. >> >> I have two questions about this: >> >> 1). Why is this not a full 16550 (ACPI_DBG2_16550_COMPATIBLE)? >> >> 2). Why is it a ACPI_DBG2_16550_SUBSET you are assuming here? > > The patch is actually applied for both ACPI_DBG2_16550_COMPATIBLE and > ACPI_DBG2_16500_SUBSET. Or I misunderstood your question? No, I had missed the fall through for both conditions since it hadn't worked in my quick boot test with the other type earlier. It's probably only applicable in the general 16550 case, not in the subset case, but I don't have any objections at this. My bad. Now as to why it's not actually triggering on my test machine is something I'll check. I set the port width in the address struct in the ACPI table to 32-bit and it didn't see mmio32 just mmio, so I then re-read the patch itself and had assumed Aleksey meant it to be only for the subtype. Be right back after I poke... Jon. -- Computer Architect | Sent from my Fedora powered laptop