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-rw-r--r--Documentation/admin-guide/kernel-parameters.txt6
-rw-r--r--arch/x86/kernel/early_printk.c29
2 files changed, 24 insertions, 11 deletions
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 92eb1f42240d..34e6800dea0e 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -1063,7 +1063,7 @@
earlyprintk=serial[,0x...[,baudrate]]
earlyprintk=ttySn[,baudrate]
earlyprintk=dbgp[debugController#]
- earlyprintk=pciserial,bus:device.function[,baudrate]
+ earlyprintk=pciserial[,force],bus:device.function[,baudrate]
earlyprintk=xdbc[xhciController#]
earlyprintk is useful when the kernel crashes before
@@ -1095,6 +1095,10 @@
The sclp output can only be used on s390.
+ The optional "force" to "pciserial" enables use of a
+ PCI device even when its classcode is not of the
+ UART class.
+
edac_report= [HW,EDAC] Control how to report EDAC event
Format: {"on" | "off" | "force"}
on: enable EDAC to report H/W event. May be overridden
diff --git a/arch/x86/kernel/early_printk.c b/arch/x86/kernel/early_printk.c
index 5e801c8c8ce7..374a52fa5296 100644
--- a/arch/x86/kernel/early_printk.c
+++ b/arch/x86/kernel/early_printk.c
@@ -213,8 +213,9 @@ static unsigned int mem32_serial_in(unsigned long addr, int offset)
* early_pci_serial_init()
*
* This function is invoked when the early_printk param starts with "pciserial"
- * The rest of the param should be ",B:D.F,baud" where B, D & F describe the
- * location of a PCI device that must be a UART device.
+ * The rest of the param should be "[force],B:D.F,baud", where B, D & F describe
+ * the location of a PCI device that must be a UART device. "force" is optional
+ * and overrides the use of an UART device with a wrong PCI class code.
*/
static __init void early_pci_serial_init(char *s)
{
@@ -224,17 +225,23 @@ static __init void early_pci_serial_init(char *s)
u32 classcode, bar0;
u16 cmdreg;
char *e;
+ int force = 0;
-
- /*
- * First, part the param to get the BDF values
- */
if (*s == ',')
++s;
if (*s == 0)
return;
+ /* Force the use of an UART device with wrong class code */
+ if (!strncmp(s, "force,", 6)) {
+ force = 1;
+ s += 6;
+ }
+
+ /*
+ * Part the param to get the BDF values
+ */
bus = (u8)simple_strtoul(s, &e, 16);
s = e;
if (*s != ':')
@@ -253,7 +260,7 @@ static __init void early_pci_serial_init(char *s)
s++;
/*
- * Second, find the device from the BDF
+ * Find the device from the BDF
*/
cmdreg = read_pci_config(bus, slot, func, PCI_COMMAND);
classcode = read_pci_config(bus, slot, func, PCI_CLASS_REVISION);
@@ -264,8 +271,10 @@ static __init void early_pci_serial_init(char *s)
*/
if (((classcode >> 16 != PCI_CLASS_COMMUNICATION_MODEM) &&
(classcode >> 16 != PCI_CLASS_COMMUNICATION_SERIAL)) ||
- (((classcode >> 8) & 0xff) != 0x02)) /* 16550 I/F at BAR0 */
- return;
+ (((classcode >> 8) & 0xff) != 0x02)) /* 16550 I/F at BAR0 */ {
+ if (!force)
+ return;
+ }
/*
* Determine if it is IO or memory mapped
@@ -289,7 +298,7 @@ static __init void early_pci_serial_init(char *s)
}
/*
- * Lastly, initialize the hardware
+ * Initialize the hardware
*/
if (*s) {
if (strcmp(s, "nocfg") == 0)