From mboxrd@z Thu Jan 1 00:00:00 1970 From: Sebastian Frias Subject: Re: [RFC PATCH] always probe UART HW when options are not specified Date: Tue, 12 Jan 2016 15:22:25 +0100 Message-ID: <56950C21.3010805@laposte.net> References: <5672D18E.8000301@laposte.net> <5672E2CF.6080705@hurleysoftware.com> <5672E76A.3010506@laposte.net> <5672F588.8070503@hurleysoftware.com> <5672FD35.5070609@laposte.net> <56731689.70702@hurleysoftware.com> <56740FC3.50302@laposte.net> <5674204C.1000907@hurleysoftware.com> <56782DE5.7090708@laposte.net> <56798EC7.1030804@laposte.net> <5693C52B.90003@laposte.net> <5693D41E.8050601@hurleysoftware.com> <5693ECBA.50003@laposte.net> <5693FD3C.5080601@hurleysoftware.com> <5694C94B.3090405@free.fr> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <5694C94B.3090405@free.fr> Sender: linux-kernel-owner@vger.kernel.org To: Mason , Peter Hurley Cc: Greg Kroah-Hartman , linux-serial@vger.kernel.org, LKML , Mans Rullgard List-Id: linux-serial@vger.kernel.org On 01/12/2016 10:37 AM, Mason wrote: > On 11/01/2016 20:06, Peter Hurley wrote: > >> I don't have enough information to suggest what you "should" use >> here. >> >> Is this going to be a shipping product? >> Is it single-core? >> etc. >> >> And what is your purpose for outputting early boot information >> before loading the serial driver which does provide console output? > > I'm not sure exactly which board Sebastian has in mind, but I've been > using the SERIAL_8250_RT288X driver on my Tango4 board. For the record, I'm using a SoC emulator, and thus do not have a bootloader per se and there are a bunch of other things that I cannot count on. The emulator has the UART pre-setup, so I just need Linux to take over without changing the parameters. Ideally, I would like to have the same image of Linux+DT to start in any instance of the emulator or real chips, regardless of the clock ratios, that's why I sort of need Linux to not change the UART speed, which is quite tricky because there are no clock generators in the emulator. NOTE: on my tree I'm using the patch I previously submitted here, so Linux is probing the UART so it works for all my cases, but I would like to go back to a standard tree. > > Note: calling the UART driver "Au1x00/RT288x" is a bit of a misnomer, > as these are names of SoCs using that distinct register layout. > The actual IP is probably the 16550-compatible Palmchip BK-3103. > https://sites.google.com/a/palmchiptech.com/palmchiptech/product-services/hardware-services/ip-cores/bk-3103 > (Not sure that this website is legitimate, though.) > > When I need earlyprintk support, I use this patch from Mans: > http://thread.gmane.org/gmane.linux.kernel/2081016 > > Regards. >