From mboxrd@z Thu Jan 1 00:00:00 1970 From: Prarit Bhargava Subject: Re: [PATCH v2] console: Add console=auto option Date: Wed, 29 Aug 2018 08:54:37 -0400 Message-ID: <8689f544-c905-3542-5d45-2d817cf86283@redhat.com> References: <728a8e68-ea4b-4040-a0fc-217df4f1928d@redhat.com> <20180816173902.18971-1-prarit@redhat.com> <20180817093828.GA10337@jagdpanzerIV> <20180817105046.GB10337@jagdpanzerIV> <9d164aa0-bc61-1bbf-f888-a24aeaf7dec0@redhat.com> <20180817125714.yekdxxqflmgajf2s@pathway.suse.cz> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20180817125714.yekdxxqflmgajf2s@pathway.suse.cz> Content-Language: en-GB Sender: linux-kernel-owner@vger.kernel.org To: Petr Mladek Cc: Sergey Senozhatsky , linux-kernel@vger.kernel.org, Mark Salter , Al Stone , "Rafael J. Wysocki" , Len Brown , Pavel Machek , x86@kernel.org, Sergey Senozhatsky , Steven Rostedt , Kees Cook , Greg Kroah-Hartman , linux-pm@vger.kernel.org, Peter Zijlstra List-Id: linux-pm@vger.kernel.org On 08/17/2018 08:57 AM, Petr Mladek wrote: > On Fri 2018-08-17 07:06:56, Prarit Bhargava wrote: >> On 08/17/2018 06:50 AM, Sergey Senozhatsky wrote: >>>> Like I mentioned to Petr, I'd like to know if you (or anyone else) has strong >>>> feelings about changing the behaviour of earlycon on x86? I could make it so >>>> that specifying just earlycon would also initialize the console. >>> >>> x86 people and/or scheduler people might have strong opinions on this. >>> I Cc-ed Peter Zijlstra; he represents both groups and is known to be >>> a hardcore earlycon user. >> >> Thanks, I'm a user of earlycon too, but only moderately. >> >> peterz, to give you an overview: Currently on x86, the SPCR information is only >> interpreted by the early console code, and can be enabled with kernel parameter >> "earlycon" (no arguments). In this patch I'm proposing adding "console=auto" >> that would enable the console based on the SPCR data. >> >> There are two options on the table. One, we could go with this patch which >> would make users do "earlycon console=auto" or, I could just change the >> behaviour of earlycon (no arguments) to also bring up the console. In the >> second case the kernel parameter would just be "earlycon". There is precedent >> for the second option as arm64 enables both the earlycon and console by default >> if SPCR is present. However, on x86, I know many users do not want the console >> enabled by default so we should keep it on demand. >> >> tl;dr: Pick one >> >> Option 1: earlycon enables both the early console and console. > > I am afraid that this is not acceptable. Users are sensitive > when a new kernel suddenly enables different consoles. For example, > see: > > + commit dac8bbbae1d0ccba9 ("Revert "printk: fix double printing with > earlycon") > > + commit c6c7d83b9c9e6a8b3 ("Revert "console: don't prefer first > registered if DT specifies stdout-path") > > > By other words, the new behavior must depend on a new option. > > >> Option 2: earlycon only enables the early console, and console=auto enables the >> console. > > I suggest: > > Option 3: "earlycon" enables early console defined by SPCR > "console" enables console defined by SPCR > > I mean that "console" without extra options would enable the console > defined by ACPI SPCR. It would work the same as "earlycon" without > extra options for early consoles. > > If you would want to make it explicit than I agree with Sergey > and would prefer "console=spcr" instead of "console=auto". I'm going with "console=spcr". FYI. P. > > Note kernel tries to enable some consoles automatically even > when "console" parameter is not defined at all. Therefore "auto" > is somehow misleading. > > Best Regards, > Petr > > PS: JFYI, I have vacation the following week... >