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From: khalasa@piap.pl (Krzysztof Hałasa)
To: Arnd Bergmann <arnd@arndb.de>
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: Wed, 20 Feb 2019 08:35:21 +0100
Message-ID: <m3y36aud3a.fsf@t19.piap.pl> (raw)
In-Reply-To: <CAK8P3a10daNVCMOSKcLTG=0-YkK4sQ0p3Uu-wM3xM5TEimUzkQ@mail.gmail.com>

Arnd Bergmann <arnd@arndb.de> writes:

> - the MMIO workarounds don't really work for a VGA card
>   in general since you cannot map the frame buffer into user
>   space, so the application of that is still a bit limited. I suspect
>   you would have had the same problem with the existing
>   ixp4xx code as well, depending on how the driver implements
>   user space graphics.

Right. Now I remember I put the VGA FB in the first 64 MB of PCI address
space (this means it was a 64 MB VGA, and that I could actually do
direct and indirect accesses at the same time). The rest of PCI address
space was used indirectly for (I guess) VGA registers and other hardware
(SATA controller and similar stuff - nothing which would require mapped
PCI memory).

The PCI bus mastering limitation was far worse - there are boards with
128 and 256 MB (maximum possible on IXP42x) of RAM and double SKB
buffering with e.g. dual gigabit Ethernet wasn't nice. I ended up with
a hack which allocated network buffers from the first 64 MB of RAM only.
-- 
Krzysztof Halasa

Industrial Research Institute for Automation and Measurements PIAP
Al. Jerozolimskie 202, 02-486 Warsaw, Poland

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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
2019-02-19  6:51                   ` khalasa
2019-02-19  9:46                     ` Arnd Bergmann
2019-02-20  7:35                       ` khalasa [this message]
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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