On Tue, Dec 5, 2023 at 2:26 PM Arnd Bergmann [off-list ref] wrote:

On Tue, Dec 5, 2023, at 10:45, Yoshinori Sato wrote:

quoted

+     if (of_property_read_u32_array(pdev->dev.of_node,
+                                    "renesas,memory", memory, 2) < 0) {
+             /*
+              * If no memory range is specified,
+              *  the entire main memory will be targeted for DMA.
+              */
+             memory[0] = memory_start;
+             memory[1] = memory_end - memory_start;
+     }

There is a generic "dma-ranges" proerty for describing
which memory is visible by a bus.

It's really a headache to use, so I put a bit of documentation here:
https://elinux.org/Device_Tree_Usage#PCI_DMA_Address_Translation

Yoshinoro, you can look at these bindings and drivers that use
dma-ranges for help:
Documentation/devicetree/bindings/pci/intel,ixp4xx-pci.yaml
drivers/pci/controller/pci-ixp4xx.c
Documentation/devicetree/bindings/pci/faraday,ftpci100.yaml
drivers/pci/controller/pci-ftpci100.c

Yours,
Linus Walleij