linux-kernel - Re: [PATCH] PCI: Add pci=safemode option

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Date:   Wed, 30 May 2018 01:22:10 -0700
From:   okaya@...eaurora.org
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     Christoph Hellwig <hch@...radead.org>, linux-pci@...r.kernel.org,
        timur@...eaurora.org, linux-arm-msm@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        Jonathan Corbet <corbet@....net>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...nel.org>,
        Christoffer Dall <cdall@...aro.org>,
        "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
        Marc Zyngier <marc.zyngier@....com>,
        Kai-Heng Feng <kai.heng.feng@...onical.com>,
        Thymo van Beers <thymovanbeers@...il.com>,
        Frederic Weisbecker <frederic@...nel.org>,
        Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
        David Rientjes <rientjes@...gle.com>,
        "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
        Keith Busch <keith.busch@...el.com>,
        Dongdong Liu <liudongdong3@...wei.com>,
        Frederick Lawler <fred@...dlawl.com>,
        Oza Pawandeep <poza@...eaurora.org>,
        Gabriele Paoloni <gabriele.paoloni@...wei.com>,
        "open list:DOCUMENTATION" <linux-doc@...r.kernel.org>,
        open list <linux-kernel@...r.kernel.org>,
        linux-pci-owner@...r.kernel.org
Subject: Re: [PATCH] PCI: Add pci=safemode option

On 2018-05-30 00:56, okaya@...eaurora.org wrote:
> On 2018-05-30 00:48, Greg Kroah-Hartman wrote:
>> On Wed, May 30, 2018 at 12:44:29AM -0700, okaya@...eaurora.org wrote:
>>> On 2018-05-30 00:37, Christoph Hellwig wrote:
>>> > On Tue, May 29, 2018 at 09:41:33PM -0700, Sinan Kaya wrote:
>>> > > Bjorn and I discussed the need for such a "safe" mode feature when you
>>> > > want to bring up PCI for a platform. You want to turn off everything
>>> > > as
>>> > > a starter and just stick to bare minimum.
>>> >
>>> > Can we please make it a config option the instead of adding code
>>> > to every kernel?  Also maybe the bringup should be in the name
>>> > to make this more clear?
>>> 
>>> One other requirement was to have a runtime option rather than 
>>> compile time
>>> option.
>>> 
>>> When someone reported a problem, we wanted to be able to say "use 
>>> this
>>> option and see if system boots" without doing any bisects or 
>>> recompilation.
>>> 
>>> This would be the first step in troubleshooting a system to see if
>>> fundamental features are working.
>> 
>> That makes sense, people can not rebuild their kernels for the most
>> part.  Putting it behind a config option would not make sense as it
>> would always have to be enabled.
>> 
> 
> Here is where the discussion took place. Last 5-10  messages should 
> help.
> 
> 
> https://bugzilla.kernel.org/show_bug.cgi?id=196197
> 

Some more paper trail for general awareness.

https://lkml.org/lkml/2018/5/3/509

> 
>>> I don't mind changing the name Bjorn mentioned safe option. I made it
>>> safemode. I am looking at Bjorn for suggestions at this moment.
>> 
>> "minimal"?  "basic"?  "crippled"?
>> "my_hardware_is_so_borked_it_needs_this_option"?  :)
>> 
>> Naming is hard...
>> 
>> greg k-h