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From: Arnd Bergmann <arnd@arndb.de>
To: linux-arm-kernel@lists.infradead.org
Cc: linux-kernel@vger.kernel.org,
	Linus Walleij <linus.walleij@linaro.org>,
	Russell King <rmk+kernel@arm.linux.org.uk>,
	Liviu Dudau <liviu.dudau@arm.com>,
	Sudeep Holla <sudeep.holla@arm.com>,
	Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>,
	Arnd Bergmann <arnd@arndb.de>,
	Russell King <linux@arm.linux.org.uk>
Subject: [PATCH 04/10] ARM: no longer force unbuffered DMA for realview
Date: Wed, 25 Nov 2015 17:32:17 +0100	[thread overview]
Message-ID: <1448469143-447355-5-git-send-email-arnd@arndb.de> (raw)
In-Reply-To: <1448469143-447355-1-git-send-email-arnd@arndb.de>

Commit 42c4dafe803dca ("ARM: 6202/1: Do not ARM_DMA_MEM_BUFFERABLE
on RealView boards with L210/L220") changed the generic setting for
ARM_DMA_MEM_BUFFERABLE to be disabled on any Realview kernel that includes
support for any of the ARM11 variations. Doing this was required to
allow doing DMA without a lockup in the l2x0 cache controller on the
Realview platform.

Unfortunately, in a kernel that also contains support for any ARMv7
based machine, the same change makes it impossible to do DMA on ARMv7,
which gets in the way of enabling multiplatform support on Realview.

As confirmed by Catalin Marinas and Linus Walleij, the current
code for Realview that we have in the kernel does not actually
perform any DMA, and this is unlikely to change in the future.
Therefore we can revert 42c4dafe803dca without introducing regressions,
but we must never start using DMA on this platform in the future.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Linus Walleij <linus.walleij@linaro.org>
Cc: Russell King <linux@arm.linux.org.uk>
---
 arch/arm/mm/Kconfig | 2 --
 1 file changed, 2 deletions(-)

diff --git a/arch/arm/mm/Kconfig b/arch/arm/mm/Kconfig
index 41218867a9a6..76f65f2d59b1 100644
--- a/arch/arm/mm/Kconfig
+++ b/arch/arm/mm/Kconfig
@@ -1005,8 +1005,6 @@ config ARM_L1_CACHE_SHIFT
 
 config ARM_DMA_MEM_BUFFERABLE
 	bool "Use non-cacheable memory for DMA" if (CPU_V6 || CPU_V6K) && !CPU_V7
-	depends on !(MACH_REALVIEW_PB1176 || REALVIEW_EB_ARM11MP || \
-		     MACH_REALVIEW_PB11MP)
 	default y if CPU_V6 || CPU_V6K || CPU_V7
 	help
 	  Historically, the kernel has used strongly ordered mappings to
-- 
2.1.0.rc2


WARNING: multiple messages have this Message-ID (diff)
From: arnd@arndb.de (Arnd Bergmann)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH 04/10] ARM: no longer force unbuffered DMA for realview
Date: Wed, 25 Nov 2015 17:32:17 +0100	[thread overview]
Message-ID: <1448469143-447355-5-git-send-email-arnd@arndb.de> (raw)
In-Reply-To: <1448469143-447355-1-git-send-email-arnd@arndb.de>

Commit 42c4dafe803dca ("ARM: 6202/1: Do not ARM_DMA_MEM_BUFFERABLE
on RealView boards with L210/L220") changed the generic setting for
ARM_DMA_MEM_BUFFERABLE to be disabled on any Realview kernel that includes
support for any of the ARM11 variations. Doing this was required to
allow doing DMA without a lockup in the l2x0 cache controller on the
Realview platform.

Unfortunately, in a kernel that also contains support for any ARMv7
based machine, the same change makes it impossible to do DMA on ARMv7,
which gets in the way of enabling multiplatform support on Realview.

As confirmed by Catalin Marinas and Linus Walleij, the current
code for Realview that we have in the kernel does not actually
perform any DMA, and this is unlikely to change in the future.
Therefore we can revert 42c4dafe803dca without introducing regressions,
but we must never start using DMA on this platform in the future.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Linus Walleij <linus.walleij@linaro.org>
Cc: Russell King <linux@arm.linux.org.uk>
---
 arch/arm/mm/Kconfig | 2 --
 1 file changed, 2 deletions(-)

diff --git a/arch/arm/mm/Kconfig b/arch/arm/mm/Kconfig
index 41218867a9a6..76f65f2d59b1 100644
--- a/arch/arm/mm/Kconfig
+++ b/arch/arm/mm/Kconfig
@@ -1005,8 +1005,6 @@ config ARM_L1_CACHE_SHIFT
 
 config ARM_DMA_MEM_BUFFERABLE
 	bool "Use non-cacheable memory for DMA" if (CPU_V6 || CPU_V6K) && !CPU_V7
-	depends on !(MACH_REALVIEW_PB1176 || REALVIEW_EB_ARM11MP || \
-		     MACH_REALVIEW_PB11MP)
 	default y if CPU_V6 || CPU_V6K || CPU_V7
 	help
 	  Historically, the kernel has used strongly ordered mappings to
-- 
2.1.0.rc2

  parent reply	other threads:[~2015-11-25 16:38 UTC|newest]

Thread overview: 32+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-11-25 16:32 [PATCH 00/10] ARM: realview multiplatform Arnd Bergmann
2015-11-25 16:32 ` Arnd Bergmann
2015-11-25 16:32 ` [PATCH 01/10] ARM: realview: remove sparsemem hack Arnd Bergmann
2015-11-25 16:32   ` Arnd Bergmann
2015-11-25 16:32 ` [PATCH 02/10] ARM: realview: don't map undefined PCI registers Arnd Bergmann
2015-11-25 16:32   ` Arnd Bergmann
2015-11-25 16:32 ` [PATCH 03/10] clk/realview: stop using machine headers Arnd Bergmann
2015-11-25 16:32   ` Arnd Bergmann
2015-11-25 16:32 ` Arnd Bergmann [this message]
2015-11-25 16:32   ` [PATCH 04/10] ARM: no longer force unbuffered DMA for realview Arnd Bergmann
2015-11-25 16:32 ` [PATCH 05/10] ARM: realview: remove private barrier implementation Arnd Bergmann
2015-11-25 16:32   ` Arnd Bergmann
2015-12-10  9:09   ` Linus Walleij
2015-12-10  9:09     ` Linus Walleij
2015-11-25 16:32 ` [PATCH 06/10] ARM: realview: enable multiplatform Arnd Bergmann
2015-11-25 16:32   ` Arnd Bergmann
2015-12-10 10:04   ` Linus Walleij
2015-12-10 10:04     ` Linus Walleij
2015-12-10 10:55     ` Arnd Bergmann
2015-12-10 10:55       ` Arnd Bergmann
2015-11-25 16:32 ` [PATCH 07/10] ARM: integrator: use explicit core module options Arnd Bergmann
2015-11-25 16:32   ` Arnd Bergmann
2015-11-25 16:32 ` [PATCH 08/10] ARM: no longer make CPU targets visible separately Arnd Bergmann
2015-11-25 16:32   ` Arnd Bergmann
2015-11-25 16:32 ` [PATCH 09/10] ARM: realview: make all header files local Arnd Bergmann
2015-11-25 16:32   ` Arnd Bergmann
2015-12-10 10:06   ` Linus Walleij
2015-12-10 10:06     ` Linus Walleij
2015-11-25 16:32 ` [PATCH 10/10] ARM: realview: clean up header files Arnd Bergmann
2015-11-25 16:32   ` Arnd Bergmann
  -- strict thread matches above, loose matches on Subject: below --
2015-02-26 16:11 [PATCH 04/10] ARM: no longer force unbuffered DMA for realview Arnd Bergmann
2015-02-27 12:24 ` Linus Walleij

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