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From: Arnd Bergmann <arnd@arndb.de>
To: "Krzysztof Hałasa" <khalasa@piap.pl>
Cc: Jason Cooper <jason@lakedaemon.net>,
	Marc Zyngier <marc.zyngier@arm.com>,
	Linus Walleij <linus.walleij@linaro.org>,
	Olof Johansson <olof@lixom.net>,
	Thomas Gleixner <tglx@linutronix.de>,
	Imre Kaloz <kaloz@openwrt.org>,
	Tim Harvey <tharvey@gateworks.com>,
	Linux ARM <linux-arm-kernel@lists.infradead.org>
Subject: Re: [PATCH 04/17 v1] irqchip: Add driver for IXP4xx
Date: Mon, 18 Feb 2019 13:44:19 +0100
Message-ID: <CAK8P3a0iubKdPrTO9ZxM+=0c3H8djpBw11KY-SO0Ai1Zgx3zHg@mail.gmail.com> (raw)
In-Reply-To: <m3bm39uwvm.fsf@t19.piap.pl>

On Mon, Feb 18, 2019 at 1:03 PM Krzysztof Hałasa <khalasa@piap.pl> wrote:
>
> Arnd Bergmann <arnd@arndb.de> writes:
>
> > I found a document that explains some of the more obscure details
> > of this chip (among a lot of the general concepts), in particular how
> > you can configure memory regions as either BE, LE-data-coherent or
> > LE-address-coherent, and the byte swap on PCI depending on that:
>
> There is also a problem with certain devices (certain old US Robotics
> access servers?) using IXP425 rev. A0. Those first chips don't have the
> LE data coherent mode.
> We (= the official Linux kernel) don't use LE data coherent mode at all,
> though I have had a patch (not very clean) which could do that.

It does sound appealing to move to data coherent mode, since that is
closer to what we have elsewhere. Maybe we can finally work that out
and then allow a little-endian multiplatform configuration to include
ixp4xx.

I have two questions about this:

- I have a vague memory that only specific revisions actually require
  the PCI indirect mode. Is it the same chip revision A0 of IXP425
  that requires both pci-indirect and address-coherent mode, or are
  there other combinations?

- How much would it hurt actual users to drop support for both
  features? I.e. do we know of anyone using the affected chips
  (and still doing updates), or are the remaining ixp4xx systems
  generally using the later chip revision?

      Arnd

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Thread overview: 43+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-02-03 21:41 [PATCH 00/17 v1] ARM: ixp4xx: Modernize and DT support Linus Walleij
2019-02-03 21:41 ` [PATCH 01/17 v1] ARM: ixp4xx: Convert to MULTI_IRQ_HANDLER Linus Walleij
2019-02-03 21:41 ` [PATCH 02/17 v1] ARM: ixp4xx: Pass IRQ resource to beeper Linus Walleij
2019-02-03 21:41 ` [PATCH 03/17 v1] ARM: ixp4xx: Convert to SPARSE_IRQ Linus Walleij
2019-02-03 21:41 ` [PATCH 04/17 v1] irqchip: Add driver for IXP4xx Linus Walleij
2019-02-11 15:30   ` Marc Zyngier
2019-02-11 20:58     ` Linus Walleij
2019-02-11 22:11       ` Marc Zyngier
2019-02-18  7:06         ` khalasa
2019-02-18  7:16           ` Linus Walleij
2019-02-18  7:35             ` khalasa
2019-02-18  9:40             ` Arnd Bergmann
2019-02-18 12:03               ` khalasa
2019-02-18 12:44                 ` Arnd Bergmann [this message]
2019-02-19  6:51                   ` khalasa
2019-02-19  9:46                     ` Arnd Bergmann
2019-02-20  7:35                       ` khalasa
2019-02-18  9:18         ` Arnd Bergmann
2019-02-03 21:41 ` [PATCH 05/17 v1] gpio: ixp4xx: Add driver for the IXP4xx GPIO Linus Walleij
2019-02-06 16:03   ` Bartosz Golaszewski
2019-02-21  8:50     ` Linus Walleij
2019-02-03 21:41 ` [PATCH 06/17 v1] ARM: ixp4xx: Switch to use new IRQ+GPIO drivers Linus Walleij
2019-02-03 21:41 ` [PATCH 07/17 v1] clocksource/drivers/ixp4xx: Add driver Linus Walleij
2019-02-03 21:41 ` [PATCH 08/17 v1] ARM: ixp4xx: Switch to use new timer driver Linus Walleij
2019-02-03 21:41 ` [PATCH 09/17 v1] irqchip: ixp4xx: Add DT bindings Linus Walleij
2019-02-18 21:25   ` Rob Herring
2019-02-03 21:41 ` [PATCH 10/17 v1] irqchip: ixp4xx: Add OF initialization support Linus Walleij
2019-02-03 21:41 ` [PATCH 11/17 v1] clocksource/drivers/ixp4xx: Add DT bindings Linus Walleij
2019-02-18 21:26   ` Rob Herring
2019-02-18 22:10     ` Daniel Lezcano
2019-02-03 21:42 ` [PATCH 12/17 v1] clocksource/drivers/ixp4xx: Add OF initialization support Linus Walleij
2019-02-11 11:26   ` Daniel Lezcano
2019-02-03 21:42 ` [PATCH 13/17 v1] gpio: ixp4xx: Add DT bindings Linus Walleij
2019-02-06 16:05   ` Bartosz Golaszewski
2019-02-18 21:27   ` Rob Herring
2019-02-03 21:42 ` [PATCH 14/17 v1] gpio: ixp4xx: Add OF probing support Linus Walleij
2019-02-06 16:13   ` Bartosz Golaszewski
2019-02-21  8:55     ` Linus Walleij
2019-02-03 21:42 ` [PATCH 15/17 v1] ARM: ixp4xx: Add DT bindings Linus Walleij
2019-02-04 15:16   ` Rob Herring
2019-02-08 19:37     ` Linus Walleij
2019-02-03 21:42 ` [PATCH 16/17 v1] ARM: ixp4xx: Add device tree boot support Linus Walleij
2019-02-03 21:42 ` [PATCH 17/17 v1] RFC: ARM: dts: Add some initial IXP4xx device trees Linus Walleij

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