[PATCH 3/7] ns8250: Add base support for MMIO UARTs

[Benjamin Herrenschmidt]

From: Benjamin Herrenschmidt <benh@amazon.com>

This adds the ability for the driver to access UARTs via MMIO instead
of PIO selectively at runtime, and exposes a new function to add an
MMIO port.

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
---
 grub-core/term/ns8250.c | 78 ++++++++++++++++++++++++++++++++---------
 grub-core/term/serial.c |  8 +++--
 include/grub/serial.h   | 11 +++++-
 3 files changed, 78 insertions(+), 19 deletions(-)

diff --git a/grub-core/term/ns8250.c b/grub-core/term/ns8250.c
index 83b25990c..b640508d0 100644
--- a/grub-core/term/ns8250.c
+++ b/grub-core/term/ns8250.c
@@ -43,6 +43,24 @@ static int dead_ports = 0;
 #define DEFAULT_BASE_CLOCK 115200
 #endif
 
+static inline unsigned char
+ns8250_reg_read (struct grub_serial_port *port, grub_addr_t reg)
+{
+  asm volatile("" : : : "memory");
+  if (port->mmio)
+    return *((volatile unsigned char *)(port->mmio_base + reg));
+  return grub_inb (port->port + reg);
+}
+
+static inline void
+ns8250_reg_write (struct grub_serial_port *port, unsigned char value, 
grub_addr_t reg)
+{
+  asm volatile("" : : : "memory");
+  if (port->mmio)
+    *((volatile char *)(port->mmio_base + reg)) = value;
+  else
+    grub_outb (value, port->port + reg);
+}
 
 /* Convert speed to divisor.  */
 static unsigned short
@@ -93,43 +111,42 @@ do_real_config (struct grub_serial_port *port)
   divisor = serial_get_divisor (port, &port->config);
 
   /* Turn off the interrupt.  */
-  grub_outb (0, port->port + UART_IER);
+  ns8250_reg_write (port, 0, UART_IER);
 
   /* Set DLAB.  */
-  grub_outb (UART_DLAB, port->port + UART_LCR);
+  ns8250_reg_write (port, UART_DLAB, UART_LCR);
 
-  /* Set the baud rate.  */
-  grub_outb (divisor & 0xFF, port->port + UART_DLL);
-  grub_outb (divisor >> 8, port->port + UART_DLH);
+  ns8250_reg_write (port, divisor & 0xFF, UART_DLL);
+  ns8250_reg_write (port, divisor >> 8, UART_DLH);
 
   /* Set the line status.  */
   status |= (parities[port->config.parity]
             | (port->config.word_len - 5)
             | stop_bits[port->config.stop_bits]);
-  grub_outb (status, port->port + UART_LCR);
+  ns8250_reg_write (port, status, UART_LCR);
 
   if (port->config.rtscts)
     {
       /* Enable the FIFO.  */
-      grub_outb (UART_ENABLE_FIFO_TRIGGER1, port->port + UART_FCR);
+      ns8250_reg_write (port, UART_ENABLE_FIFO_TRIGGER1, UART_FCR);
 
       /* Turn on DTR and RTS.  */
-      grub_outb (UART_ENABLE_DTRRTS, port->port + UART_MCR);
+      ns8250_reg_write (port, UART_ENABLE_DTRRTS, UART_MCR);
     }
   else
     {
       /* Enable the FIFO.  */
-      grub_outb (UART_ENABLE_FIFO_TRIGGER14, port->port + UART_FCR);
+      ns8250_reg_write (port, UART_ENABLE_FIFO_TRIGGER14, UART_FCR);
 
       /* Turn on DTR, RTS, and OUT2.  */
-      grub_outb (UART_ENABLE_DTRRTS | UART_ENABLE_OUT2, port->port + UART_MCR);
+      ns8250_reg_write (port, UART_ENABLE_DTRRTS | UART_ENABLE_OUT2, UART_MCR);
     }
 
   /* Drain the input buffer.  */
   endtime = grub_get_time_ms () + 1000;
-  while (grub_inb (port->port + UART_LSR) & UART_DATA_READY)
+  while (ns8250_reg_read (port, UART_LSR) & UART_DATA_READY)
     {
-      grub_inb (port->port + UART_RX);
+      ns8250_reg_read (port, UART_RX);
       if (grub_get_time_ms () > endtime)
        {
          port->broken = 1;
@@ -145,8 +162,8 @@ static int
 serial_hw_fetch (struct grub_serial_port *port)
 {
   do_real_config (port);
-  if (grub_inb (port->port + UART_LSR) & UART_DATA_READY)
-    return grub_inb (port->port + UART_RX);
+  if (ns8250_reg_read (port, UART_LSR) & UART_DATA_READY)
+    return ns8250_reg_read (port, UART_RX);
 
   return -1;
 }
@@ -166,7 +183,7 @@ serial_hw_put (struct grub_serial_port *port, const int c)
   else
     endtime = grub_get_time_ms () + 200;
   /* Wait until the transmitter holding register is empty.  */
-  while ((grub_inb (port->port + UART_LSR) & UART_EMPTY_TRANSMITTER) == 0)
+  while ((ns8250_reg_read (port, UART_LSR) & UART_EMPTY_TRANSMITTER) == 0)
     {
       if (grub_get_time_ms () > endtime)
        {
@@ -179,7 +196,7 @@ serial_hw_put (struct grub_serial_port *port, const int c)
   if (port->broken)
     port->broken--;
 
-  grub_outb (c, port->port + UART_TX);
+  ns8250_reg_write (port, c, UART_TX);
 }
 
 /* Initialize a serial device. PORT is the port number for a serial device.
@@ -262,6 +279,7 @@ grub_ns8250_init (void)
        com_ports[i].name = com_names[i];
        com_ports[i].driver = &grub_ns8250_driver;
        com_ports[i].port = serial_hw_io_addr[i];
+       com_ports[i].mmio = 0;
        err = grub_serial_config_defaults (&com_ports[i]);
        if (err)
          grub_print_error ();
@@ -316,8 +334,36 @@ grub_serial_ns8250_add_port (grub_port_t port)
     }
   p->driver = &grub_ns8250_driver;
   grub_serial_config_defaults (p);
+  p->mmio = 0;
   p->port = port;
   grub_serial_register (p);
 
   return p->name;
 }
+
+char *
+grub_serial_ns8250_add_mmio(grub_addr_t addr)
+{
+  struct grub_serial_port *p;
+  unsigned i;
+  for (i = 0; i < GRUB_SERIAL_PORT_NUM; i++)
+    if (com_ports[i].mmio &&  com_ports[i].mmio_base == addr)
+       return com_names[i];
+
+  p = grub_malloc (sizeof (*p));
+  if (!p)
+    return NULL;
+  p->name = grub_xasprintf ("mmio,%llx", (unsigned long long) addr);
+  if (!p->name)
+    {
+      grub_free (p);
+      return NULL;
+    }
+  p->driver = &grub_ns8250_driver;
+  grub_serial_config_defaults (p);
+  p->mmio = 1;
+  p->mmio_base = addr;
+  grub_serial_register (p);
+
+  return p->name;
+}
diff --git a/grub-core/term/serial.c b/grub-core/term/serial.c
index 842322b1c..c8f5f02db 100644
--- a/grub-core/term/serial.c
+++ b/grub-core/term/serial.c
@@ -201,8 +201,12 @@ grub_cmd_serial (grub_extcmd_context_t ctxt, int argc, 
char **args)
 
   if (state[OPTION_PORT].set)
     {
-      grub_snprintf (pname, sizeof (pname), "port%lx",
-                    grub_strtoul (state[1].arg, 0, 0));
+      if (grub_memcmp (state[OPTION_PORT].arg, "mmio", 4) == 0)
+          grub_snprintf(pname, sizeof (pname), "%s", state[1].arg);
+      else
+          grub_snprintf (pname, sizeof (pname), "port%lx",
+                         grub_strtoul (state[1].arg, 0, 0));
+
       name = pname;
     }
 
diff --git a/include/grub/serial.h b/include/grub/serial.h
index 67379de45..ccf464d41 100644
--- a/include/grub/serial.h
+++ b/include/grub/serial.h
@@ -86,9 +86,17 @@ struct grub_serial_port
    */
   union
   {
+    struct
+    {
+      int mmio;
+      union
+      {
 #if defined(__mips__) || defined (__i386__) || defined (__x86_64__)
-    grub_port_t port;
+        grub_port_t port;
 #endif
+        grub_addr_t mmio_base;
+      };
+    };
     struct
     {
       grub_usb_device_t usbdev;
@@ -178,6 +186,7 @@ grub_serial_config_defaults (struct grub_serial_port *port)
 #if defined(__mips__) || defined (__i386__) || defined (__x86_64__)
 void grub_ns8250_init (void);
 char *grub_serial_ns8250_add_port (grub_port_t port);
+char *grub_serial_ns8250_add_mmio(grub_addr_t addr);
 #endif
 #ifdef GRUB_MACHINE_IEEE1275
 void grub_ofserial_init (void);
-- 
2.34.1