[PATCH v6] usb: dwc3: core: add support for realtek SoCs custom's global register start address

[Stanley Chang]

The Realtek RTD SoCs were designed with the global register address
offset at 0x8100. The default address offset is constant at
DWC3_GLOBALS_REGS_START (0xc100). Therefore, add a check if the
compatible name of the parent is realtek,rtd-dwc3, then global
register start address will remap to 0x8100.

Signed-off-by: Stanley Chang <stanley_chang@xxxxxxxxxxx>
---
 v5 to v6 change:
Change the compatible name to avoid using the wildcard.

 v4 to v5 change:
Use the compatible name of the parent to match this special offset.

 v3 to v4 change:
Use the compatible name to specify the global register address offset.
If the compatible name is "snps,dwc3-rtk-soc", then the offset use 0x8100.
Otherwise, the offset is default value 0xc100.

 v2 to v3 change:
1.  Fix the dtschema validation error.

 v1 to v2 change:
1. Change the name of the property "snps,global-regs-starting-offset".
2. Adjust the format of comment.
3. Add initial value of the global_regs_starting_offset
4. Remove the log of dev_info.
---
 drivers/usb/dwc3/core.c | 11 +++++++++++
 drivers/usb/dwc3/core.h |  2 ++
 2 files changed, 13 insertions(+)

diff --git a/drivers/usb/dwc3/core.c b/drivers/usb/dwc3/core.c
index 0beaab932e7d..278cd1c33841 100644
--- a/drivers/usb/dwc3/core.c
+++ b/drivers/usb/dwc3/core.c
@@ -1800,6 +1800,17 @@ static int dwc3_probe(struct platform_device *pdev)
 	dwc_res = *res;
 	dwc_res.start += DWC3_GLOBALS_REGS_START;
 
+	if (dev->of_node) {
+		struct device_node *parent = of_get_parent(dev->of_node);
+
+		if (of_device_is_compatible(parent, "realtek,rtd-dwc3")) {
+			dwc_res.start -= DWC3_GLOBALS_REGS_START;
+			dwc_res.start += DWC3_RTK_RTD_GLOBALS_REGS_START;
+		}
+
+		of_node_put(parent);
+	}
+
 	regs = devm_ioremap_resource(dev, &dwc_res);
 	if (IS_ERR(regs))
 		return PTR_ERR(regs);
diff --git a/drivers/usb/dwc3/core.h b/drivers/usb/dwc3/core.h
index d56457c02996..1968638f29ed 100644
--- a/drivers/usb/dwc3/core.h
+++ b/drivers/usb/dwc3/core.h
@@ -84,6 +84,8 @@
 #define DWC3_OTG_REGS_START		0xcc00
 #define DWC3_OTG_REGS_END		0xccff
 
+#define DWC3_RTK_RTD_GLOBALS_REGS_START	0x8100
+
 /* Global Registers */
 #define DWC3_GSBUSCFG0		0xc100
 #define DWC3_GSBUSCFG1		0xc104
-- 
2.34.1