drivers/char: allow using both dbgp=xhci and dbgp=ehci

This allows configuring EHCI and XHCI consoles separately,
simultaneously, such that e.g. one can be used for the console and the
other by the debugger.

This changes string_param() to custom_param() in both ehci and xhci
drivers. Both drivers parse only values applicable to them.

Suggested-by: Jan Beulich <jbeulich@suse.com>
Signed-off-by: Marek Marczykowski-Górecki <marmarek@invisiblethingslab.com>
Acked-by: Jan Beulich <jbeulich@suse.com>

docs/misc/xen-command-line.pandoc

@@ -409,7 +409,7 @@ The following are examples of correct specifications:
 Specify the size of the console ring buffer.
 
 ### console
-> `= List of [ vga | com1[H,L] | com2[H,L] | pv | dbgp | none ]`
+> `= List of [ vga | com1[H,L] | com2[H,L] | pv | dbgp | xhci | none ]`
 
 > Default: `console=com1,vga`
 
@@ -428,7 +428,9 @@ cleared.  This allows a single port to be shared by two subsystems
 `pv` indicates that Xen should use Xen's PV console. This option is
 only available when used together with `pv-in-pvh`.
 
-`dbgp` indicates that Xen should use a USB debug port.
+`dbgp` indicates that Xen should use a USB2 debug port.
+
+`xhci` indicates that Xen should use a USB3 debug port.
 
 `none` indicates that Xen should not use a console.  This option only
 makes sense on its own.

xen/drivers/char/ehci-dbgp.c

@@ -1464,7 +1464,17 @@ static struct uart_driver __read_mostly ehci_dbgp_driver = {
 static struct ehci_dbgp ehci_dbgp = { .state = dbgp_unsafe, .phys_port = 1 };
 
 static char __initdata opt_dbgp[30];
-string_param("dbgp", opt_dbgp);
+
+static int __init parse_ehci_dbgp(const char *opt)
+{
+    if ( strncmp(opt, "ehci", 4) )
+        return 0;
+
+    strlcpy(opt_dbgp, opt, sizeof(opt_dbgp));
+
+    return 0;
+}
+custom_param("dbgp", parse_ehci_dbgp);
 
 void __init ehci_dbgp_init(void)
 {
@@ -1472,7 +1482,7 @@ void __init ehci_dbgp_init(void)
     u32 debug_port, offset, bar_val;
     const char *e;
 
-    if ( strncmp(opt_dbgp, "ehci", 4) )
+    if ( !opt_dbgp[0] )
         return;
 
     if ( isdigit(opt_dbgp[4]) || !opt_dbgp[4] )

xen/drivers/char/serial.c

@@ -311,6 +311,12 @@ int __init serial_parse_handle(const char *conf)
         goto common;
     }
 
+    if ( !strncmp(conf, "xhci", 4) && (!conf[4] || conf[4] == ',') )
+    {
+        handle = SERHND_XHCI;
+        goto common;
+    }
+
     if ( !strncmp(conf, "dtuart", 6) )
     {
         handle = SERHND_DTUART;

xen/drivers/char/xhci-dbc.c

@@ -245,6 +245,7 @@ struct dbc {
     uint64_t xhc_dbc_offset;
     void __iomem *xhc_mmio;
 
+    bool enable; /* whether dbgp=xhci was set at all */
     bool open;
     unsigned int xhc_num; /* look for n-th xhc */
 };
@@ -1058,18 +1059,14 @@ static struct xhci_dbc_ctx ctx __aligned(16);
 static uint8_t out_wrk_buf[DBC_WORK_RING_CAP];
 static struct xhci_string_descriptor str_buf[DBC_STRINGS_COUNT];
 
-static char __initdata opt_dbgp[30];
-
-string_param("dbgp", opt_dbgp);
-
-void __init xhci_dbc_uart_init(void)
+static int __init xhci_parse_dbgp(const char *opt_dbgp)
 {
     struct dbc_uart *uart = &dbc_uart;
     struct dbc *dbc = &uart->dbc;
     const char *e;
 
     if ( strncmp(opt_dbgp, "xhci", 4) )
-        return;
+        return 0;
 
     memset(dbc, 0, sizeof(*dbc));
 
@@ -1087,12 +1084,26 @@ void __init xhci_dbc_uart_init(void)
             printk(XENLOG_ERR
                    "Invalid dbgp= PCI device spec: '%s'\n",
                    opt_dbgp + 8);
-            return;
+            return -EINVAL;
         }
 
         dbc->sbdf = PCI_SBDF(0, bus, slot, func);
     }
 
+    dbc->enable = true;
+
+    return 0;
+}
+custom_param("dbgp", xhci_parse_dbgp);
+
+void __init xhci_dbc_uart_init(void)
+{
+    struct dbc_uart *uart = &dbc_uart;
+    struct dbc *dbc = &uart->dbc;
+
+    if ( !dbc->enable )
+        return;
+
     dbc->dbc_ctx = &ctx;
     dbc->dbc_erst = &erst;
     dbc->dbc_ering.trb = evt_trb;
@@ -1102,7 +1113,7 @@ void __init xhci_dbc_uart_init(void)
     dbc->dbc_str = str_buf;
 
     if ( dbc_open(dbc) )
-        serial_register_uart(SERHND_DBGP, &dbc_uart_driver, &dbc_uart);
+        serial_register_uart(SERHND_XHCI, &dbc_uart_driver, &dbc_uart);
 }
 
 #ifdef DBC_DEBUG

xen/include/xen/serial.h

@@ -91,10 +91,11 @@ struct uart_driver {
 };
 
 /* 'Serial handles' are composed from the following fields. */
-#define SERHND_IDX      (3<<0) /* COM1, COM2, DBGP, DTUART?               */
+#define SERHND_IDX      (3<<0) /* COM1, COM2, DBGP, XHCI, DTUART?         */
 # define SERHND_COM1    (0<<0)
 # define SERHND_COM2    (1<<0)
 # define SERHND_DBGP    (2<<0)
+# define SERHND_XHCI    (3<<0)
 # define SERHND_DTUART  (0<<0) /* Steal SERHND_COM1 value */
 #define SERHND_HI       (1<<2) /* Mux/demux each transferred char by MSB. */
 #define SERHND_LO       (1<<3) /* Ditto, except that the MSB is cleared.  */