linux-kernel - [PATCH v2 5/6] powerpc/pseries/iommu: Make use of DDW even if it does not map the partition

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Date:   Wed, 24 Jun 2020 03:24:10 -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>,
        Leonardo Bras <leobras.c@...il.com>,
        Alexey Kardashevskiy <aik@...abs.ru>,
        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 v2 5/6] powerpc/pseries/iommu: Make use of DDW even if it does not map the partition

As of today, if a DDW is created and can't map the whole partition, it's
removed and the default DMA window "ibm,dma-window" is used instead.

Usually this DDW is bigger than the default DMA window, so it would be
better to make use of it instead.

Signed-off-by: Leonardo Bras <leobras.c@...il.com>
---
 arch/powerpc/platforms/pseries/iommu.c | 28 +++++++++++++++++---------
 1 file changed, 19 insertions(+), 9 deletions(-)

diff --git a/arch/powerpc/platforms/pseries/iommu.c b/arch/powerpc/platforms/pseries/iommu.c
index 4fcf00016fb1..2d217cda4075 100644
--- a/arch/powerpc/platforms/pseries/iommu.c
+++ b/arch/powerpc/platforms/pseries/iommu.c
@@ -685,7 +685,7 @@ static void pci_dma_bus_setup_pSeriesLP(struct pci_bus *bus)
 	struct iommu_table *tbl;
 	struct device_node *dn, *pdn;
 	struct pci_dn *ppci;
-	const __be32 *dma_window = NULL;
+	const __be32 *dma_window = NULL, *alt_dma_window = NULL;
 
 	dn = pci_bus_to_OF_node(bus);
 
@@ -699,8 +699,13 @@ static void pci_dma_bus_setup_pSeriesLP(struct pci_bus *bus)
 			break;
 	}
 
+	/* If there is a DDW available, use it instead */
+	alt_dma_window = of_get_property(pdn, DIRECT64_PROPNAME, NULL);
+	if (alt_dma_window)
+		dma_window = alt_dma_window;
+
 	if (dma_window == NULL) {
-		pr_debug("  no ibm,dma-window property !\n");
+		pr_debug("  no ibm,dma-window nor linux,direct64-ddr-window-info property !\n");
 		return;
 	}
 
@@ -1166,16 +1171,19 @@ static u64 enable_ddw(struct pci_dev *dev, struct device_node *pdn)
 			  query.page_size);
 		goto out_failed;
 	}
+
 	/* verify the window * number of ptes will map the partition */
-	/* check largest block * page size > max memory hotplug addr */
 	max_addr = ddw_memory_hotplug_max();
 	if (query.largest_available_block < (max_addr >> page_shift)) {
-		dev_dbg(&dev->dev, "can't map partition max 0x%llx with %llu "
-			  "%llu-sized pages\n", max_addr,  query.largest_available_block,
-			  1ULL << page_shift);
-		goto out_failed;
+		dev_dbg(&dev->dev, "can't map partition max 0x%llx with %llu %llu-sized pages\n",
+			max_addr, query.largest_available_block,
+			1ULL << page_shift);
+
+		len = order_base_2(query.largest_available_block << page_shift);
+	} else {
+		len = order_base_2(max_addr);
 	}
-	len = order_base_2(max_addr);
+
 	win64 = kzalloc(sizeof(struct property), GFP_KERNEL);
 	if (!win64) {
 		dev_info(&dev->dev,
@@ -1229,7 +1237,9 @@ static u64 enable_ddw(struct pci_dev *dev, struct device_node *pdn)
 	list_add(&window->list, &direct_window_list);
 	spin_unlock(&direct_window_list_lock);
 
-	dma_addr = be64_to_cpu(ddwprop->dma_base);
+	/* Only returns the dma_addr if DDW maps the whole partition */
+	if (len == order_base_2(max_addr))
+		dma_addr = be64_to_cpu(ddwprop->dma_base);
 	goto out_unlock;
 
 out_free_window:
-- 
2.25.4