linux-kernel - [PATCH 0/5] iommu/sun50i: Allwinner D1 support

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Date:   Wed, 27 Apr 2022 20:03:55 -0500
From:   Samuel Holland <samuel@...lland.org>
To:     Joerg Roedel <joro@...tes.org>, Will Deacon <will@...nel.org>,
        iommu@...ts.linux-foundation.org
Cc:     Heiko Stuebner <heiko@...ech.de>,
        Palmer Dabbelt <palmer@...belt.com>,
        linux-riscv@...ts.infradead.org,
        Samuel Holland <samuel@...lland.org>,
        Chen-Yu Tsai <wens@...e.org>,
        Jernej Skrabec <jernej.skrabec@...il.com>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Maxime Ripard <mripard@...nel.org>,
        Philipp Zabel <p.zabel@...gutronix.de>,
        Rob Herring <robh+dt@...nel.org>, devicetree@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-sunxi@...ts.linux.dev
Subject: [PATCH 0/5] iommu/sun50i: Allwinner D1 support

D1 is a RISC-V SoC from Allwinner's sunxi family. This series adds IOMMU
binding and driver support.

One piece is still missing to use the IOMMU for DMA allocations: a call
to iommu_setup_dma_ops(). On ARM64 this is handled by the architecture's
code. RISC-V does not currently select ARCH_HAS_SETUP_DMA_OPS, but it
will once Zicbom support[1] is merged.

[1]: https://lore.kernel.org/lkml/20220307224620.1933061-2-heiko@sntech.de/

So I cannot follow virtio-iommu.c and call iommu_setup_dma_ops() when
ARCH_HAS_SETUP_DMA_OPS=n. However, if I apply the following patch on top
of Heiko's non-coherent DMA series, the display engine successfully uses
the IOMMU to allocate its framebuffer:

--- a/arch/riscv/mm/dma-noncoherent.c
+++ b/arch/riscv/mm/dma-noncoherent.c
@@ -6,6 +6,7 @@
  */

 #include <linux/dma-direct.h>
+#include <linux/dma-iommu.h>
 #include <linux/dma-map-ops.h>
 #include <linux/mm.h>

@@ -53,4 +54,7 @@
 {
 	/* If a specific device is dma-coherent, set it here */
 	dev->dma_coherent = coherent;
+
+	if (iommu)
+		iommu_setup_dma_ops(dev, dma_base, dma_base + size - 1);
 }


Samuel Holland (5):
  dt-bindings: iommu: sun50i: Add compatible for Allwinner D1
  iommu/sun50i: Support variants without an external reset
  iommu/sun50i: Ensure bypass is disabled
  iommu/sun50i: Add support for the D1 variant
  iommu/sun50i: Ensure the IOMMU can be used for DMA

 .../iommu/allwinner,sun50i-h6-iommu.yaml      | 16 +++++++++++--
 drivers/iommu/Kconfig                         |  1 +
 drivers/iommu/sun50i-iommu.c                  | 24 +++++++++++++++++--
 3 files changed, 37 insertions(+), 4 deletions(-)

-- 
2.35.1