linux-kernel - [PATCH v6 09/12] x86: early_printk: add USB3 debug port earlyprintk support

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Message-Id: <1453781665-4714-10-git-send-email-baolu.lu@linux.intel.com>
Date:	Tue, 26 Jan 2016 12:14:22 +0800
From:	Lu Baolu <baolu.lu@...ux.intel.com>
To:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:	linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org,
	Lu Baolu <baolu.lu@...ux.intel.com>
Subject: [PATCH v6 09/12] x86: early_printk: add USB3 debug port earlyprintk support

Add support for early printk by writing debug messages to the USB3
debug port. Users can use this type of early printk by specifying
kernel parameter of "earlyprintk=xdbc". This gives users a chance
of providing debug output.

Signed-off-by: Lu Baolu <baolu.lu@...ux.intel.com>
---
 Documentation/kernel-parameters.txt |  1 +
 arch/x86/kernel/early_printk.c      |  5 +++++
 drivers/usb/early/xhci-dbc.c        | 43 +++++++++++++++++++++++++++++++++++++
 include/linux/usb/xhci-dbc.h        |  5 +++++
 4 files changed, 54 insertions(+)

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 87d40a7..460dc73 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -1067,6 +1067,7 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
 			earlyprintk=ttySn[,baudrate]
 			earlyprintk=dbgp[debugController#]
 			earlyprintk=pciserial,bus:device.function[,baudrate]
+			earlyprintk=xdbc[xhciController#]
 
 			earlyprintk is useful when the kernel crashes before
 			the normal console is initialized. It is not enabled by
diff --git a/arch/x86/kernel/early_printk.c b/arch/x86/kernel/early_printk.c
index 21bf924..ba4c471 100644
--- a/arch/x86/kernel/early_printk.c
+++ b/arch/x86/kernel/early_printk.c
@@ -17,6 +17,7 @@
 #include <asm/intel-mid.h>
 #include <asm/pgtable.h>
 #include <linux/usb/ehci_def.h>
+#include <linux/usb/xhci-dbc.h>
 #include <linux/efi.h>
 #include <asm/efi.h>
 #include <asm/pci_x86.h>
@@ -373,6 +374,10 @@ static int __init setup_early_printk(char *buf)
 		if (!strncmp(buf, "dbgp", 4) && !early_dbgp_init(buf + 4))
 			early_console_register(&early_dbgp_console, keep);
 #endif
+#ifdef CONFIG_EARLY_PRINTK_XDBC
+		if (!strncmp(buf, "xdbc", 4) && !early_xdbc_init(buf + 4))
+			early_console_register(&early_xdbc_console, keep);
+#endif
 #ifdef CONFIG_HVC_XEN
 		if (!strncmp(buf, "xen", 3))
 			early_console_register(&xenboot_console, keep);
diff --git a/drivers/usb/early/xhci-dbc.c b/drivers/usb/early/xhci-dbc.c
index 344d93e..6c24ba0 100644
--- a/drivers/usb/early/xhci-dbc.c
+++ b/drivers/usb/early/xhci-dbc.c
@@ -10,6 +10,7 @@
  * it under the terms of the GNU General Public License version 2 as
  * published by the Free Software Foundation.
  */
+#include <linux/console.h>
 #include <linux/pci_regs.h>
 #include <linux/pci_ids.h>
 #include <linux/bootmem.h>
@@ -1319,3 +1320,45 @@ int xdbc_bulk_write(const char *bytes, int size)
 
 	return ret;
 }
+
+/*
+ * Start a bulk-in or bulk-out transfer, wait until transfer completion
+ * or error. Return the count of actually transferred bytes or error.
+ */
+static void early_xdbc_write(struct console *con, const char *str, u32 n)
+{
+	int chunk, ret;
+	static char buf[XDBC_MAX_PACKET];
+	int use_cr = 0;
+
+	if (!xdbcp->xdbc_reg)
+		return;
+	memset(buf, 0, XDBC_MAX_PACKET);
+	while (n > 0) {
+		for (chunk = 0; chunk < XDBC_MAX_PACKET && n > 0;
+		     str++, chunk++, n--) {
+			if (!use_cr && *str == '\n') {
+				use_cr = 1;
+				buf[chunk] = '\r';
+				str--;
+				n++;
+				continue;
+			}
+			if (use_cr)
+				use_cr = 0;
+			buf[chunk] = *str;
+		}
+		if (chunk > 0) {
+			ret = xdbc_bulk_write(buf, chunk);
+			if (ret < 0)
+				break;
+		}
+	}
+}
+
+struct console early_xdbc_console = {
+	.name =		"earlyxdbc",
+	.write =	early_xdbc_write,
+	.flags =	CON_PRINTBUFFER,
+	.index =	-1,
+};
diff --git a/include/linux/usb/xhci-dbc.h b/include/linux/usb/xhci-dbc.h
index 289ba58..a556eb8 100644
--- a/include/linux/usb/xhci-dbc.h
+++ b/include/linux/usb/xhci-dbc.h
@@ -216,4 +216,9 @@ struct xdbc_state {
 #define	xdbc_read64(regs)	xhci_read_64(NULL, (regs))
 #define	xdbc_write64(val, regs)	xhci_write_64(NULL, (val), (regs))
 
+#ifdef CONFIG_EARLY_PRINTK_XDBC
+extern int early_xdbc_init(char *s);
+extern struct console early_xdbc_console;
+#endif /* CONFIG_EARLY_PRINTK_XDBC */
+
 #endif /* __LINUX_XHCI_DBC_H */
-- 
2.1.4