linux-kernel - [PATCH 05/12] usb: xhci: dbc: add debug buffer

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Date:	Wed, 28 Oct 2015 16:00:36 +0800
From:	Lu Baolu <baolu.lu@...ux.intel.com>
To:	Mathias Nyman <mathias.nyman@...el.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Alan Stern <stern@...land.harvard.edu>
Cc:	linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org,
	Lu Baolu <baolu.lu@...ux.intel.com>
Subject: [PATCH 05/12] usb: xhci: dbc: add debug buffer

"printk" is not suitable for dbc debugging especially when console
is in usage. This patch adds a debug buffer in dbc driver and puts
the debug messages in this local buffer. The debug buffer could be
dumped whenever the console is not in use. This part of code will
not be visible unless DBC_DEBUG is defined.

Signed-off-by: Lu Baolu <baolu.lu@...ux.intel.com>
---
 drivers/usb/early/xhci-dbc.c | 62 ++++++++++++++++++++++++++++++++++++++++++--
 1 file changed, 60 insertions(+), 2 deletions(-)

diff --git a/drivers/usb/early/xhci-dbc.c b/drivers/usb/early/xhci-dbc.c
index 6b23f09..b36a527 100644
--- a/drivers/usb/early/xhci-dbc.c
+++ b/drivers/usb/early/xhci-dbc.c
@@ -32,8 +32,64 @@ static struct xdbc_state xdbc_stat;
 static struct xdbc_state *xdbcp = &xdbc_stat;
 
 #ifdef DBC_DEBUG
-/* place holder */
-#define	xdbc_trace	printk
+#define	XDBC_DEBUG_BUF_SIZE	(PAGE_SIZE * 32)
+#define	MSG_MAX_LINE		128
+static char xdbc_debug_buf[XDBC_DEBUG_BUF_SIZE];
+static void xdbc_trace(const char *fmt, ...)
+{
+	int i, size;
+	va_list args;
+	static int pos;
+	char temp_buf[MSG_MAX_LINE];
+
+	if (pos >= XDBC_DEBUG_BUF_SIZE - 1)
+		return;
+
+	memset(temp_buf, 0, MSG_MAX_LINE);
+	va_start(args, fmt);
+	vsnprintf(temp_buf, MSG_MAX_LINE - 1, fmt, args);
+	va_end(args);
+
+	i = 0;
+	size = strlen(temp_buf);
+	while (i < size) {
+		xdbc_debug_buf[pos] = temp_buf[i];
+		pos++;
+		i++;
+
+		if (pos >= XDBC_DEBUG_BUF_SIZE - 1)
+			break;
+	}
+}
+
+static void xdbc_dump_debug_buffer(void)
+{
+	int index = 0;
+	int count = 0;
+	char dump_buf[MSG_MAX_LINE];
+
+	xdbc_trace("The end of DbC trace buffer\n");
+	pr_notice("DBC debug buffer:\n");
+	memset(dump_buf, 0, MSG_MAX_LINE);
+
+	while (index < XDBC_DEBUG_BUF_SIZE) {
+		if (!xdbc_debug_buf[index])
+			break;
+
+		if (xdbc_debug_buf[index] == '\n' ||
+				count >= MSG_MAX_LINE - 1) {
+			pr_notice("DBC: @%08x %s\n", index, dump_buf);
+			memset(dump_buf, 0, MSG_MAX_LINE);
+			count = 0;
+		} else {
+			dump_buf[count] = xdbc_debug_buf[index];
+			count++;
+		}
+
+		index++;
+	}
+}
+
 static void xdbc_dbg_dump_regs(char *str)
 {
 	if (!xdbcp->xdbc_reg) {
@@ -165,6 +221,7 @@ static void xdbc_dbg_dump_data(char *str)
 
 #else
 static inline void xdbc_trace(const char *fmt, ...) { }
+static inline void xdbc_dump_debug_buffer(void) { }
 static inline void xdbc_dbg_dump_regs(char *str) { }
 static inline void xdbc_dbg_dump_data(char *str) { }
 #endif	/* DBC_DEBUG */
@@ -832,6 +889,7 @@ int __init early_xdbc_init(char *s)
 		pr_notice("failed to setup xHCI DbC connection\n");
 		xdbcp->xhci_base = NULL;
 		xdbcp->xdbc_reg = NULL;
+		xdbc_dump_debug_buffer();
 		return ret;
 	}
 
-- 
2.1.4

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