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From: Robin Murphy <robin.murphy@arm.com>
To: liviu.dudau@arm.com, sudeep.holla@arm.com, lorenzo.pieralisi@arm.com
Cc: linux-arm-kernel@lists.infradead.org,
	Anders Roxell <anders.roxell@linaro.org>
Subject: [PATCH] arm64: dts: juno: Remove GICv2m dma-range
Date: Mon, 24 Jan 2022 17:57:01 +0000	[thread overview]
Message-ID: <856c3f7192c6c3ce545ba67462f2ce9c86ed6b0c.1643046936.git.robin.murphy@arm.com> (raw)

Although it is painstakingly honest to describe all 3 PCI windows in
"dma-ranges", it misses the the subtle distinction that the window for
the GICv2m range is normally programmed for Device memory attributes
rather than Normal Cacheable like the DRAM windows. Since MMU-401 only
offers stage 2 translation, this means that when the PCI SMMU is
enabled, accesses through that IPA range unexpectedly lose coherency if
mapped as cacheable at the SMMU, due to the attribute combining rules.
Since an extra 256KB is neither here nor there when we still have 10GB
worth of usable address space, rather than attempting to describe and
cope with this detail let's just remove the offending range. If the SMMU
is not used then it makes no difference anyway.

Fixes: 4ac4d146cb63 ("arm64: dts: juno: Describe PCI dma-ranges")
Reported-by: Anders Roxell <anders.roxell@linaro.org>
Signed-off-by: Robin Murphy <robin.murphy@arm.com>
---

Sorry it took a while to catch up on this...

 arch/arm64/boot/dts/arm/juno-base.dtsi | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/arch/arm64/boot/dts/arm/juno-base.dtsi b/arch/arm64/boot/dts/arm/juno-base.dtsi
index 6288e104a089..a2635b14da30 100644
--- a/arch/arm64/boot/dts/arm/juno-base.dtsi
+++ b/arch/arm64/boot/dts/arm/juno-base.dtsi
@@ -543,8 +543,7 @@ pcie_ctlr: pcie@40000000 {
 			 <0x02000000 0x00 0x50000000 0x00 0x50000000 0x0 0x08000000>,
 			 <0x42000000 0x40 0x00000000 0x40 0x00000000 0x1 0x00000000>;
 		/* Standard AXI Translation entries as programmed by EDK2 */
-		dma-ranges = <0x02000000 0x0 0x2c1c0000 0x0 0x2c1c0000 0x0 0x00040000>,
-			     <0x02000000 0x0 0x80000000 0x0 0x80000000 0x0 0x80000000>,
+		dma-ranges = <0x02000000 0x0 0x80000000 0x0 0x80000000 0x0 0x80000000>,
 			     <0x43000000 0x8 0x00000000 0x8 0x00000000 0x2 0x00000000>;
 		#interrupt-cells = <1>;
 		interrupt-map-mask = <0 0 0 7>;
-- 
2.28.0.dirty


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             reply	other threads:[~2022-01-24 18:22 UTC|newest]

Thread overview: 3+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-01-24 17:57 Robin Murphy [this message]
2022-01-25 15:24 ` [PATCH] arm64: dts: juno: Remove GICv2m dma-range Liviu Dudau
2022-01-26 10:26 ` Sudeep Holla

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