Re: [RFC PATCH 00/11] Removing Calxeda platform support

From: Florian Fainelli <f.fainelli@gmail.com>
To: Rob Herring <robh@kernel.org>, Andre Przywara <andre.przywara@arm.com>
Cc: Mark Langsdorf <mlangsdo@redhat.com>,
	kvm@vger.kernel.org, Viresh Kumar <viresh.kumar@linaro.org>,
	"open list:LIBATA SUBSYSTEM (Serial and Parallel ATA drivers)" 
	<linux-ide@vger.kernel.org>, Will Deacon <will@kernel.org>,
	linux-clk <linux-clk@vger.kernel.org>,
	soc@kernel.org, Joerg Roedel <joro@8bytes.org>,
	Daniel Lezcano <daniel.lezcano@linaro.org>,
	devicetree@vger.kernel.org, Jon Loeliger <jdl@jdl.com>,
	"open list:THERMAL" <linux-pm@vger.kernel.org>,
	Eric Auger <eric.auger@redhat.com>,
	Alex Williamson <alex.williamson@redhat.com>,
	Tony Luck <tony.luck@intel.com>, Alexander Graf <graf@amazon.com>,
	Mauro Carvalho Chehab <mchehab@kernel.org>,
	"moderated list:ARM/FREESCALE IMX / MXC ARM ARCHITECTURE" 
	<linux-arm-kernel@lists.infradead.org>,
	linux-edac <linux-edac@vger.kernel.org>,
	Jens Axboe <axboe@kernel.dk>,
	Matthias Brugger <mbrugger@suse.com>,
	Stephen Boyd <sboyd@kernel.org>, netdev <netdev@vger.kernel.org>,
	Cornelia Huck <cohuck@redhat.com>,
	"Rafael J. Wysocki" <rjw@rjwysocki.net>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	Linux IOMMU <iommu@lists.linux-foundation.org>,
	Robert Richter <rrichter@marvell.com>,
	James Morse <james.morse@arm.com>, Borislav Petkov <bp@alien8.de>,
	Robin Murphy <robin.murphy@arm.com>,
	"David S. Miller" <davem@davemloft.net>
Subject: Re: [RFC PATCH 00/11] Removing Calxeda platform support
Date: Tue, 18 Feb 2020 10:51:17 -0800	[thread overview]
Message-ID: <f2b15018-2b88-01b8-14f1-a6c326b10b58@gmail.com> (raw)
In-Reply-To: <CAL_JsqJpDLn5Zr2UHno1TeReqrwZ-HAAfd78AouigGi4sAQuOw@mail.gmail.com>

On 2/18/20 10:40 AM, Rob Herring wrote:
> On Tue, Feb 18, 2020 at 12:14 PM Andre Przywara <andre.przywara@arm.com> wrote:
>>
>> On Tue, 18 Feb 2020 11:13:10 -0600
>> Rob Herring <robh@kernel.org> wrote:
>>
>> Hi,
>>
>>> Calxeda has been defunct for 6 years now. Use of Calxeda servers carried
>>> on for some time afterwards primarily as distro builders for 32-bit ARM.
>>> AFAIK, those systems have been retired in favor of 32-bit VMs on 64-bit
>>> hosts.
>>>
>>> The other use of Calxeda Midway I'm aware of was testing 32-bit ARM KVM
>>> support as there are few or no other systems with enough RAM and LPAE. Now
>>> 32-bit KVM host support is getting removed[1].
>>>
>>> While it's not much maintenance to support, I don't care to convert the
>>> Calxeda DT bindings to schema nor fix any resulting errors in the dts files
>>> (which already don't exactly match what's shipping in firmware).
>>
>> While every kernel maintainer seems always happy to take patches with a negative diffstat, I wonder if this is really justification enough to remove a perfectly working platform. I don't really know about any active users, but experience tells that some platforms really are used for quite a long time, even if they are somewhat obscure. N900 or Netwinder, anyone?
>>
>> So to not give the impression that actually *everyone* (from that small subset of people actively reading the kernel list) is happy with that, I think that having support for at least Midway would be useful. On the one hand it's a decent LPAE platform (with memory actually exceeding 4GB), and on the other hand it's something with capable I/O (SATA) and networking, so one can actually stress test the system. Which is the reason I was using that for KVM testing, but even with that probably going away now there remain still some use cases, and be it for general ARM(32) testing.
> 
> Does LPAE with more than 4GB actually need to work if there's not
> another platform out there?

There are ARCH_BRCMSTB platforms that are 32-bit only and have 6GB of
DRAM populated, and those continue to work just fine, though there is no
known use for KVM AFAICT.
-- 
Florian