[PATCH kernel v4 06/19] powerpc/pseries/iommu: Use memory@ nodes in max RAM address calculation

[Alexey Kardashevskiy <aik@ozlabs.ru>]

We might have memory@ nodes with "linux,usable-memory" set to zero
(for example, to replicate powernv's behaviour for GPU coherent memory)
which means that the memory needs an extra initialization but since
it can be used afterwards, the pseries platform will try mapping it
for DMA so the DMA window needs to cover those memory regions too;
if the window cannot cover new memory regions, the memory onlining fails.

This walks through the memory nodes to find the highest RAM address to
let a huge DMA window cover that too in case this memory gets onlined
later.

Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
---
Changes:
v4:
* uses of_read_number directly instead of cut-n-pasted read_n_cells
---
 arch/powerpc/platforms/pseries/iommu.c | 34 +++++++++++++++++++++++++-
 1 file changed, 33 insertions(+), 1 deletion(-)

diff --git a/arch/powerpc/platforms/pseries/iommu.c b/arch/powerpc/platforms/pseries/iommu.c
index 06f0296..7da74b5 100644
--- a/arch/powerpc/platforms/pseries/iommu.c
+++ b/arch/powerpc/platforms/pseries/iommu.c
@@ -964,6 +964,38 @@ struct failed_ddw_pdn {
 
 static LIST_HEAD(failed_ddw_pdn_list);
 
+static phys_addr_t ddw_memory_hotplug_max(void)
+{
+	phys_addr_t max_addr = memory_hotplug_max();
+	struct device_node *memory;
+
+	for_each_node_by_type(memory, "memory") {
+		unsigned long start, size;
+		int ranges, n_mem_addr_cells, n_mem_size_cells, len;
+		const __be32 *memcell_buf;
+
+		memcell_buf = of_get_property(memory, "reg", &len);
+		if (!memcell_buf || len <= 0)
+			continue;
+
+		n_mem_addr_cells = of_n_addr_cells(memory);
+		n_mem_size_cells = of_n_size_cells(memory);
+
+		/* ranges in cell */
+		ranges = (len >> 2) / (n_mem_addr_cells + n_mem_size_cells);
+
+		/* these are order-sensitive, and modify the buffer pointer */
+		start = of_read_number(memcell_buf, n_mem_addr_cells);
+		memcell_buf += n_mem_addr_cells;
+		size = of_read_number(memcell_buf, n_mem_size_cells);
+		memcell_buf += n_mem_size_cells;
+
+		max_addr = max_t(phys_addr_t, max_addr, start + size);
+	}
+
+	return max_addr;
+}
+
 /*
  * If the PE supports dynamic dma windows, and there is space for a table
  * that can map all pages in a linear offset, then setup such a table,
@@ -1053,7 +1085,7 @@ static u64 enable_ddw(struct pci_dev *dev, struct device_node *pdn)
 	}
 	/* verify the window * number of ptes will map the partition */
 	/* check largest block * page size > max memory hotplug addr */
-	max_addr = memory_hotplug_max();
+	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 %u "
 			  "%llu-sized pages\n", max_addr,  query.largest_available_block,
-- 
2.17.1