How does the kernel determine the resource flags of a device node in a device tree?

On further debugging, I observed that the parsing of "ranges' property fails at this point:

To give the sequence:

altera_pcie_probe() -> altera_pcie_parse_request_of_pci_ranges() -> of_pci_get_host_bridge_resources()

In of_pci_get_host_bridge_resources(), there is a call to of_pci_range_parser_init(), and then a loop for_each_of_pci_range(&parser, &range), as below:

/* Check for ranges property */

err = of_pci_range_parser_init(&parser, dev);

if (err)

goto parse_failed;

pr_debug("Parsing ranges property...\n");

for_each_of_pci_range(&parser, &range) {

pr_info("inside for_each_of_pci_range...\n");

/* Read next ranges element */

if ((range.flags & IORESOURCE_TYPE_BITS) == IORESOURCE_IO)

snprintf(range_type, 4, " IO");

else if ((range.flags & IORESOURCE_TYPE_BITS) == IORESOURCE_MEM)

snprintf(range_type, 4, "MEM");

else

snprintf(range_type, 4, "err");

pr_info(" %s %#010llx..%#010llx -> %#010llx\n", range_type,

range.cpu_addr, range.cpu_addr + range.size - 1,

range.pci_addr);

/* some code goes here */

}

What I observed is, the loop is not entered at all, which means the previous function of_pci_range_parser_init() hasn't done it's job properly.

Let me paste a portion of my DTS file again below:

sopc0: sopc@0 {

device_type = "soc";

ranges;

# address-cells = <1>;

# size-cells = <1>;

compatible = "ALTR,avalon", "simple-bus";

bus-frequency = <0>;

test_subsys_pcie: pcie@0x000000000 {

compatible = "altera, my-pcie";

reg = <0xc0000000 0x00001000>,

<0xc0001000 0x00010000>,

<0xff200000 0x00010000>;

reg-names = "axi_slave_1", "axi_slave_2", "axi_slave_3";

interrupt-parent = <&HPS_arm_gic_0>;

interrupts = <0 19 4>;

clocks = <&test_subsys_clk_125M>;

device_type = "pci";

bus-range = <0x00000000 0x000000ff>;

# address-cells = <1>;

# size-cells = <1>;

ranges = <0x00000000 0xc0000000 0x00001000>;

}; //end unknown@0x000000000 (test_subsys_pcie)

I expect the of_pci_range_parser_init() function to figure out the ranges correctly in the DTS. Is there anything wrong with the way I've declared the "ranges" in DTS ? If the parsing by of_pci_range_parser_init() is wrong, it should've returned an error, but it didn't; It succeeded; But the loop for_each_of_pci_range(&parser, &range) fails to take off !

Inside of_pci_range_parser_init(), I printed the the foll.:

parser->range=c1ff789c, parser->end=c1ff78a8, len=12

The difference between 0x c1ff789c and 0x c1ff78a8 is 12 i.e. 12 bytes. But what does this length indicate??

The parser structure is defined in linux/of_address.h as follows:

struct of_pci_range_parser {

struct device_node *node;

const __be32 *range;

const __be32 *end;

int np;

int pna;

};

What does the range and end mean here? I want to understand this w.r.to the ranges I've declared

ranges = <0x00000000 0xc0000000 0x00001000>.

In the loop for_each_of_pci_range(&parser, &range), the 2nd argument is a pointer to the foll. Structure:

struct of_pci_range {

u32 pci_space;

u64 pci_addr;

u64 cpu_addr;

u64 size;

u32 flags;

};

Similary I want to understand the of_pci_range structure w.r.to the "ranges" property in DTS.

What is the link among struct of_pci_range_parser, struct of_pci_range, and "ranges" property in DTS? Going through the code is pretty confusing. Can someone explain?