linux-kernel - [PATCH v3 5/6] powerpc/pseries/iommu: Make use of DDW even if it does not map the partition

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Date:   Fri,  3 Jul 2020 03:18:43 -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 v3 5/6] powerpc/pseries/iommu: Make use of DDW even if it does not map the partition

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

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

The ddw created will be used for direct mapping by default.
If it's not available, indirect mapping sill be used instead.

As there will never have both mappings at the same time, the same property
name can be used for the created DDW.

So renaming
define DIRECT64_PROPNAME "linux,direct64-ddr-window-info"
to
define DMA64_PROPNAME "linux,dma64-ddr-window-info"
looks the right thing to do.

Signed-off-by: Leonardo Bras <leobras.c@...il.com>
---
 arch/powerpc/platforms/pseries/iommu.c | 38 ++++++++++++++++----------
 1 file changed, 24 insertions(+), 14 deletions(-)

diff --git a/arch/powerpc/platforms/pseries/iommu.c b/arch/powerpc/platforms/pseries/iommu.c
index 5b520ac354c6..c652177de09c 100644
--- a/arch/powerpc/platforms/pseries/iommu.c
+++ b/arch/powerpc/platforms/pseries/iommu.c
@@ -364,7 +364,7 @@ static LIST_HEAD(direct_window_list);
 static DEFINE_SPINLOCK(direct_window_list_lock);
 /* protects initializing window twice for same device */
 static DEFINE_MUTEX(direct_window_init_mutex);
-#define DIRECT64_PROPNAME "linux,direct64-ddr-window-info"
+#define DMA64_PROPNAME "linux,dma64-ddr-window-info"
 
 static int tce_clearrange_multi_pSeriesLP(unsigned long start_pfn,
 					unsigned long num_pfn, const void *arg)
@@ -690,7 +690,7 @@ 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);
 
@@ -704,8 +704,13 @@ 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, DMA64_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,dma64-ddr-window-info property !\n");
 		return;
 	}
 
@@ -823,7 +828,7 @@ static void remove_ddw(struct device_node *np, bool remove_prop)
 	if (ret)
 		return;
 
-	win = of_find_property(np, DIRECT64_PROPNAME, NULL);
+	win = of_find_property(np, DMA64_PROPNAME, NULL);
 	if (!win)
 		return;
 
@@ -869,8 +874,8 @@ static int find_existing_ddw_windows(void)
 	if (!firmware_has_feature(FW_FEATURE_LPAR))
 		return 0;
 
-	for_each_node_with_property(pdn, DIRECT64_PROPNAME) {
-		direct64 = of_get_property(pdn, DIRECT64_PROPNAME, &len);
+	for_each_node_with_property(pdn, DMA64_PROPNAME) {
+		direct64 = of_get_property(pdn, DMA64_PROPNAME, &len);
 		if (!direct64)
 			continue;
 
@@ -1205,23 +1210,26 @@ static u64 enable_ddw(struct pci_dev *dev, struct device_node *pdn)
 			  query.page_size);
 		goto out_restore_defwin;
 	}
+
 	/* 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_restore_defwin;
+		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,
 			"couldn't allocate property for 64bit dma window\n");
 		goto out_restore_defwin;
 	}
-	win64->name = kstrdup(DIRECT64_PROPNAME, GFP_KERNEL);
+	win64->name = kstrdup(DMA64_PROPNAME, GFP_KERNEL);
 	win64->value = ddwprop = kmalloc(sizeof(*ddwprop), GFP_KERNEL);
 	win64->length = sizeof(*ddwprop);
 	if (!win64->name || !win64->value) {
@@ -1268,7 +1276,9 @@ 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