linux-kernel - [PATCH 4/4] powerpc/pseries/iommu: Remove default DMA window before creating DDW

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Date:   Fri, 19 Jun 2020 02:06:20 -0300
From:   Leonardo Bras <leobras.c@...il.com>
To:     Michael Ellerman <mpe@...erman.id.au>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Alexey Kardashevskiy <aik@...abs.ru>,
        Leonardo Bras <leobras.c@...il.com>,
        Thiago Jung Bauermann <bauerman@...ux.ibm.com>,
        Ram Pai <linuxram@...ibm.com>
Cc:     linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org
Subject: [PATCH 4/4] powerpc/pseries/iommu: Remove default DMA window before creating DDW

On LoPAR "DMA Window Manipulation Calls", it's recommended to remove the
default DMA window for the device, before attempting to configure a DDW,
in order to make the maximum resources available for the next DDW to be
created.

This is a requirement for some devices to use DDW, given they only
allow one DMA window.

If setting up a new DDW fails anywhere after the removal of this
default DMA window, restore it using reset_dma_window.

Signed-off-by: Leonardo Bras <leobras.c@...il.com>
---
 arch/powerpc/platforms/pseries/iommu.c | 20 +++++++++++++++++---
 1 file changed, 17 insertions(+), 3 deletions(-)

diff --git a/arch/powerpc/platforms/pseries/iommu.c b/arch/powerpc/platforms/pseries/iommu.c
index de633f6ae093..68d1ea957ac7 100644
--- a/arch/powerpc/platforms/pseries/iommu.c
+++ b/arch/powerpc/platforms/pseries/iommu.c
@@ -1074,8 +1074,9 @@ static u64 enable_ddw(struct pci_dev *dev, struct device_node *pdn)
 	u64 dma_addr, max_addr;
 	struct device_node *dn;
 	u32 ddw_avail[3];
+
 	struct direct_window *window;
-	struct property *win64;
+	struct property *win64, *dfl_win;
 	struct dynamic_dma_window_prop *ddwprop;
 	struct failed_ddw_pdn *fpdn;
 
@@ -1110,8 +1111,19 @@ static u64 enable_ddw(struct pci_dev *dev, struct device_node *pdn)
 	if (ret)
 		goto out_failed;
 
-       /*
-	 * Query if there is a second window of size to map the
+	/*
+	 * First step of setting up DDW is removing the default DMA window,
+	 * if it's present. It will make all the resources available to the
+	 * new DDW window.
+	 * If anything fails after this, we need to restore it.
+	 */
+
+	dfl_win = of_find_property(pdn, "ibm,dma-window", NULL);
+	if (dfl_win)
+		remove_dma_window(pdn, ddw_avail, dfl_win);
+
+	/*
+	 * Query if there is a window of size to map the
 	 * whole partition.  Query returns number of windows, largest
 	 * block assigned to PE (partition endpoint), and two bitmasks
 	 * of page sizes: supported and supported for migrate-dma.
@@ -1219,6 +1231,8 @@ static u64 enable_ddw(struct pci_dev *dev, struct device_node *pdn)
 	kfree(win64);
 
 out_failed:
+	if (dfl_win)
+		reset_dma_window(dev, pdn);
 
 	fpdn = kzalloc(sizeof(*fpdn), GFP_KERNEL);
 	if (!fpdn)
-- 
2.25.4