usb: dwc3: add tracepoints to aid debugging

When we're debugging hard-to-reproduce and time-sensitive
use cases, printk() poses too much overhead. That's when
the kernel's tracing infrastructure comes into play.

This patch implements a few initial tracepoints for the
dwc3 driver. More traces can be added as necessary in order
to ease the task of debugging dwc3.

Reviewed-by: Paul Zimmerman <paulz@synopsys.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>

drivers/usb/dwc3/io.h

@@ -20,27 +20,51 @@
 #define __DRIVERS_USB_DWC3_IO_H
 
 #include <linux/io.h>
-
+#include "trace.h"
+#include "debug.h"
 #include "core.h"
 
 static inline u32 dwc3_readl(void __iomem *base, u32 offset)
 {
+	u32 offs = offset - DWC3_GLOBALS_REGS_START;
+	u32 value;
+
 	/*
 	 * We requested the mem region starting from the Globals address
 	 * space, see dwc3_probe in core.c.
 	 * However, the offsets are given starting from xHCI address space.
 	 */
-	return readl(base + (offset - DWC3_GLOBALS_REGS_START));
+	value = readl(base + offs);
+
+	/*
+	 * When tracing we want to make it easy to find the correct address on
+	 * documentation, so we revert it back to the proper addresses, the
+	 * same way they are described on SNPS documentation
+	 */
+	dwc3_trace(trace_dwc3_readl, "addr %p value %08x",
+			base - DWC3_GLOBALS_REGS_START + offset, value);
+
+	return value;
 }
 
 static inline void dwc3_writel(void __iomem *base, u32 offset, u32 value)
 {
+	u32 offs = offset - DWC3_GLOBALS_REGS_START;
+
 	/*
 	 * We requested the mem region starting from the Globals address
 	 * space, see dwc3_probe in core.c.
 	 * However, the offsets are given starting from xHCI address space.
 	 */
-	writel(value, base + (offset - DWC3_GLOBALS_REGS_START));
+	writel(value, base + offs);
+
+	/*
+	 * When tracing we want to make it easy to find the correct address on
+	 * documentation, so we revert it back to the proper addresses, the
+	 * same way they are described on SNPS documentation
+	 */
+	dwc3_trace(trace_dwc3_writel, "addr %p value %08x",
+			base - DWC3_GLOBALS_REGS_START + offset, value);
 }
 
 #endif /* __DRIVERS_USB_DWC3_IO_H */