console: add EHCI debug port based serial console

Low level hardware interface pieces adapted from Linux.

For setup information, see Linux'es Documentation/x86/earlyprintk.txt
and/or http://www.coreboot.org/EHCI_Debug_Port.

Signed-off-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Acked-by: Keir Fraser <keir@xen.org>

docs/misc/xen-command-line.markdown

@@ -244,7 +244,7 @@ A typical setup for most situations might be `com1=115200,8n1`
 Specify the size of the console ring buffer.
 
 ### console
-> `= List of [ vga | com1[H,L] | com2[H,L] | none ]`
+> `= List of [ vga | com1[H,L] | com2[H,L] | dbgp | none ]`
 
 > Default: `console=com1,vga`
 
@@ -260,6 +260,8 @@ the converse; transmitted and received characters will have their MSB
 cleared.  This allows a single port to be shared by two subsystems
 (e.g. console and debugger).
 
+`dbgp` indicates that Xen should use a USB debug port.
+
 `none` indicates that Xen should not use a console.  This option only
 makes sense on its own.
 
@@ -352,6 +354,12 @@ combination with the `low_crashinfo` command line option.
 ### credit2\_load\_window\_shift
 > `= <integer>`
 
+### dbgp
+> `= ehci[ <integer> | @pci<bus>:<slot>.<func> ]`
+
+Specify the USB controller to use, either by instance number (when going
+over the PCI busses sequentially) or by PCI device (must be on segment 0).
+
 ### debug\_stack\_lines
 > `= <integer>`
 

xen/arch/x86/Rules.mk

@@ -7,6 +7,7 @@ HAS_CPUFREQ := y
 HAS_PCI := y
 HAS_PASSTHROUGH := y
 HAS_NS16550 := y
+HAS_EHCI := y
 HAS_KEXEC := y
 HAS_GDBSX := y
 xenoprof := y

xen/arch/x86/physdev.c

@@ -8,6 +8,7 @@
 #include <xen/event.h>
 #include <xen/guest_access.h>
 #include <xen/iocap.h>
+#include <xen/serial.h>
 #include <asm/current.h>
 #include <asm/io_apic.h>
 #include <asm/msi.h>
@@ -722,6 +723,19 @@ ret_t do_physdev_op(int cmd, XEN_GUEST_HANDLE(void) arg)
 
         break;
     }
+
+    case PHYSDEVOP_dbgp_op: {
+        struct physdev_dbgp_op op;
+
+        if ( !IS_PRIV(v->domain) )
+            ret = -EPERM;
+        else if ( copy_from_guest(&op, arg, 1) )
+            ret = -EFAULT;
+        else
+            ret = dbgp_op(&op);
+        break;
+    }
+
     default:
         ret = -ENOSYS;
         break;

xen/arch/x86/setup.c

@@ -606,6 +606,7 @@ void __init __start_xen(unsigned long mbi_p)
     ns16550.io_base = 0x2f8;
     ns16550.irq     = 3;
     ns16550_init(1, &ns16550);
+    ehci_dbgp_init();
     console_init_preirq();
 
     printk("Bootloader: %s\n", loader);

xen/drivers/char/Makefile

@@ -1,4 +1,5 @@
 obj-y += console.o
 obj-$(HAS_NS16550) += ns16550.o
 obj-$(HAS_PL011) += pl011.o
+obj-$(HAS_EHCI) += ehci-dbgp.o
 obj-y += serial.o

xen/drivers/char/serial.c

@@ -265,6 +265,14 @@ int __init serial_parse_handle(char *conf)
 {
     int handle;
 
+    if ( !strncmp(conf, "dbgp", 4) && (!conf[4] || conf[4] == ',') )
+    {
+        if ( !com[SERHND_DBGP].driver )
+            goto fail;
+
+        return SERHND_DBGP | SERHND_COOKED;
+    }
+
     if ( strncmp(conf, "com", 3) )
         goto fail;
 

xen/include/asm-x86/fixmap.h

@@ -36,7 +36,15 @@
  * from the end of virtual memory backwards.
  */
 enum fixed_addresses {
-    FIX_RESERVED, /* Index 0 is reserved since fix_to_virt(0) > FIXADDR_TOP. */
+    /* Index 0 is reserved since fix_to_virt(0) == FIXADDR_TOP. */
+    FIX_RESERVED,
+    /*
+     * Indexes using the page tables set up before entering __start_xen()
+     * must be among the first (L1_PAGETABLE_ENTRIES - 1) entries.
+     * These are generally those needed by the various console drivers.
+     */
+    FIX_EHCI_DBGP,
+    /* Everything else should go further down. */
 #ifdef __i386__
     FIX_PAE_HIGHMEM_0,
     FIX_PAE_HIGHMEM_END = FIX_PAE_HIGHMEM_0 + NR_CPUS-1,

xen/include/public/physdev.h

@@ -312,6 +312,24 @@ struct physdev_pci_device {
 typedef struct physdev_pci_device physdev_pci_device_t;
 DEFINE_XEN_GUEST_HANDLE(physdev_pci_device_t);
 
+#define PHYSDEVOP_DBGP_RESET_PREPARE    1
+#define PHYSDEVOP_DBGP_RESET_DONE       2
+
+#define PHYSDEVOP_DBGP_BUS_UNKNOWN      0
+#define PHYSDEVOP_DBGP_BUS_PCI          1
+
+#define PHYSDEVOP_dbgp_op               29
+struct physdev_dbgp_op {
+    /* IN */
+    uint8_t op;
+    uint8_t bus;
+    union {
+        struct physdev_pci_device pci;
+    } u;
+};
+typedef struct physdev_dbgp_op physdev_dbgp_op_t;
+DEFINE_XEN_GUEST_HANDLE(physdev_dbgp_op_t);
+
 /*
  * Notify that some PIRQ-bound event channels have been unmasked.
  * ** This command is obsolete since interface version 0x00030202 and is **

xen/include/xen/serial.h

@@ -69,9 +69,10 @@ struct uart_driver {
 };
 
 /* 'Serial handles' are composed from the following fields. */
-#define SERHND_IDX      (3<<0) /* COM1 or COM2?                           */
+#define SERHND_IDX      (3<<0) /* COM1, COM2, or DBGP?                    */
 # define SERHND_COM1    (0<<0)
 # define SERHND_COM2    (1<<0)
+# define SERHND_DBGP    (2<<0)
 #define SERHND_HI       (1<<2) /* Mux/demux each transferred char by MSB. */
 #define SERHND_LO       (1<<3) /* Ditto, except that the MSB is cleared.  */
 #define SERHND_COOKED   (1<<4) /* Newline/carriage-return translation?    */
@@ -142,9 +143,13 @@ struct ns16550_defaults {
     unsigned long io_base; /* default io_base address */
 };
 void ns16550_init(int index, struct ns16550_defaults *defaults);
+void ehci_dbgp_init(void);
 
 void pl011_init(int index, unsigned long register_base_address);
 
+struct physdev_dbgp_op;
+int dbgp_op(const struct physdev_dbgp_op *);
+
 /* Baud rate was pre-configured before invoking the UART driver. */
 #define BAUD_AUTO (-1)