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@xxxxxxxxxxxxxxx>
---
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 22a4b68..b65b07f 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -1032,6 +1032,7 @@ 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 eec40f5..5341a16 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 aaf655f..68a7139 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>
@@ -1332,3 +1333,45 @@ 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
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