Re: [PATCH v2 2/3] term/serial: Add support for PCI serial devices

[Peter Zijlstra <peterz@infradead.org>]

On Wed, Dec 21, 2022 at 01:59:02PM +0100, Daniel Kiper wrote:
> Sorry for late reply...
> 
> May I ask you to send the patches using "git send-email"?

I'll try -- I'm one of the few quilt holdouts in Linux-land so I don't
have much experience with it.


> Please add a blurb how to use this driver to the docs/grub.texi file.
> 
> > GRUB_TERMINAL="serial console"
> >
> > Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
> > ---
> >
> > Index: grub/grub-core/Makefile.core.def
> > ===================================================================
> > --- grub.orig/grub-core/Makefile.core.def
> > +++ grub/grub-core/Makefile.core.def
> > @@ -2047,6 +2047,7 @@ module = {
> >    ieee1275 = term/ieee1275/serial.c;
> >    mips_arc = term/arc/serial.c;
> >    efi = term/efi/serial.c;
> > +  pci = term/pci/serial.c;
> 
> I think this should be "x86 = term/pci/serial.c".

I thought the whole purpose of Glenn's patch was to allow doing the 'pci
=' thing, so that all platforms that support PCI get to have the
benefit.

But if you really want I can make it 'x86 =' ofcourse.


> > +static int
> > +find_pciserial (grub_pci_device_t dev, grub_pci_id_t pciid, void *data)
> 
> grub_pci_id_t pciid __attribute__ ((unused))
> 
> > +{
> > +  grub_pci_address_t cmd_addr, class_addr, bar_addr;
> > +  struct grub_serial_port *port;
> > +  grub_uint32_t class, bar;
> > +  grub_uint16_t cmdreg;
> > +  int *port_num = data;
> > +  grub_err_t err;
> > +
> > +  (void)pciid;
> 
> ... and please drop this...
> 

> > +error:
> 
> s/error/fail/
> 
> And please add a space before label...

All done, except the Makefile thing, find the updated version below.
I'll attempt to git-send-email both patches once we agree on the
Makefile hunk.


---
Subject: term/serial: Add support for PCI serial devices

Loosely based on early_pci_serial_init() from Linux, allow GRUB to make
use of PCI serial devices.

Specifically, my Alderlake NUC exposes the Intel AMT SoL UART as a PCI
enumerated device but doesn't include it in the EFI tables.

Tested and confirmed working on a "Lenovo P360 Tiny" with Intel AMT
enabled. This specific machine has (from lspci -vv):

00:16.3 Serial controller: Intel Corporation Device 7aeb (rev 11) (prog-if 02 [16550])
        DeviceName: Onboard - Other
        Subsystem: Lenovo Device 330e
        Control: I/O+ Mem+ BusMaster- SpecCycle- MemWINV- VGASnoop- ParErr- Stepping- SERR- FastB2B- DisINTx-
        Status: Cap+ 66MHz+ UDF- FastB2B+ ParErr- DEVSEL=fast >TAbort- <TAbort- <MAbort- >SERR- <PERR- INTx-
        Interrupt: pin D routed to IRQ 19
        Region 0: I/O ports at 40a0 [size=8]
        Region 1: Memory at b4224000 (32-bit, non-prefetchable) [size=4K]
        Capabilities: [40] MSI: Enable- Count=1/1 Maskable- 64bit+
                Address: 0000000000000000  Data: 0000
        Capabilities: [50] Power Management version 3
                Flags: PMEClk- DSI+ D1- D2- AuxCurrent=0mA PME(D0-,D1-,D2-,D3hot-,D3cold-)
                Status: D0 NoSoftRst+ PME-Enable- DSel=0 DScale=0 PME-
        Kernel driver in use: serial

From which the following config (/etc/default/grub) gets a working
serial setup:

GRUB_CMDLINE_LINUX="console=tty0 earlyprintk=pciserial,00:16.3,115200 console=ttyS0,115200"
GRUB_SERIAL_COMMAND="serial --speed=115200 pci_00:16.3"
GRUB_TERMINAL="serial console"

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Tested-by: Glenn Washburn <development@efficientek.com>
Reviewed-by: Glenn Washburn <development@efficientek.com>
---

Index: grub/grub-core/Makefile.core.def
===================================================================
--- grub.orig/grub-core/Makefile.core.def
+++ grub/grub-core/Makefile.core.def
@@ -2057,6 +2057,7 @@ module = {
   ieee1275 = term/ieee1275/serial.c;
   mips_arc = term/arc/serial.c;
   efi = term/efi/serial.c;
+  pci = term/pci/serial.c;
 
   enable = terminfomodule;
   enable = ieee1275;
Index: grub/grub-core/term/pci/serial.c
===================================================================
--- /dev/null
+++ grub/grub-core/term/pci/serial.c
@@ -0,0 +1,93 @@
+/*
+ *  GRUB  --  GRand Unified Bootloader
+ *  Copyright (C) 2022  Free Software Foundation, Inc.
+ *
+ *  GRUB is free software: you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation, either version 3 of the License, or
+ *  (at your option) any later version.
+ *
+ *  GRUB is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with GRUB.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <grub/serial.h>
+#include <grub/term.h>
+#include <grub/types.h>
+#include <grub/pci.h>
+#include <grub/mm.h>
+#include <grub/misc.h>
+
+static int
+find_pciserial (grub_pci_device_t dev,
+		grub_pci_id_t pciid __attribute__ ((unused)),
+		void *data __attribute__ ((unused)))
+{
+  grub_pci_address_t cmd_addr, class_addr, bar_addr;
+  struct grub_serial_port *port;
+  grub_uint32_t class, bar;
+  grub_uint16_t cmdreg;
+  grub_err_t err;
+
+  cmd_addr = grub_pci_make_address (dev, GRUB_PCI_REG_COMMAND);
+  cmdreg = grub_pci_read (cmd_addr);
+
+  class_addr = grub_pci_make_address (dev, GRUB_PCI_REG_REVISION);
+  class = grub_pci_read (class_addr);
+
+  bar_addr = grub_pci_make_address (dev, GRUB_PCI_REG_ADDRESS_REG0);
+  bar = grub_pci_read (bar_addr);
+
+  /* 16550 compatible MODEM or SERIAL */
+  if (((class >> 16) != GRUB_PCI_CLASS_COMMUNICATION_MODEM &&
+       (class >> 16) != GRUB_PCI_CLASS_COMMUNICATION_SERIAL) ||
+      ((class >> 8) & 0xff) != GRUB_PCI_SERIAL_16550_COMPATIBLE)
+    return 0;
+
+  if ((bar & GRUB_PCI_ADDR_SPACE_MASK) != GRUB_PCI_ADDR_SPACE_IO)
+    return 0;
+
+  port = grub_zalloc (sizeof (*port));
+  if (port == NULL)
+    return 0;
+
+  port->name = grub_xasprintf ("pci_%02x:%02x.%x",
+			       grub_pci_get_bus (dev),
+			       grub_pci_get_device (dev),
+			       grub_pci_get_function (dev));
+  if (port->name == NULL)
+    goto fail;
+
+  grub_pci_write (cmd_addr, cmdreg | GRUB_PCI_COMMAND_IO_ENABLED);
+
+  port->driver = &grub_ns8250_driver;
+  port->port = bar & GRUB_PCI_ADDR_IO_MASK;
+  err = grub_serial_config_defaults (port);
+  if (err != GRUB_ERR_NONE)
+    {
+      grub_print_error ();
+      goto fail;
+    }
+
+  err = grub_serial_register (port);
+  if (err != GRUB_ERR_NONE)
+    goto fail;
+
+  return 0;
+
+ fail:
+  grub_free (port->name);
+  grub_free (port);
+  return 0;
+}
+
+void
+grub_pciserial_init (void)
+{
+  grub_pci_iterate (find_pciserial, NULL);
+}
Index: grub/grub-core/term/serial.c
===================================================================
--- grub.orig/grub-core/term/serial.c
+++ grub/grub-core/term/serial.c
@@ -505,6 +505,9 @@ GRUB_MOD_INIT(serial)
 #ifdef GRUB_MACHINE_ARC
   grub_arcserial_init ();
 #endif
+#ifdef GRUB_HAS_PCI
+  grub_pciserial_init ();
+#endif
 }
 
 GRUB_MOD_FINI(serial)
Index: grub/include/grub/pci.h
===================================================================
--- grub.orig/include/grub/pci.h
+++ grub/include/grub/pci.h
@@ -80,8 +80,13 @@
 
 #define  GRUB_PCI_STATUS_DEVSEL_TIMING_SHIFT 9
 #define  GRUB_PCI_STATUS_DEVSEL_TIMING_MASK 0x0600
+
 #define  GRUB_PCI_CLASS_SUBCLASS_VGA  0x0300
 #define  GRUB_PCI_CLASS_SUBCLASS_USB  0x0c03
+#define  GRUB_PCI_CLASS_COMMUNICATION_SERIAL  0x0700
+#define  GRUB_PCI_CLASS_COMMUNICATION_MODEM   0x0703
+
+#define  GRUB_PCI_SERIAL_16550_COMPATIBLE 0x02
 
 #ifndef ASM_FILE
 
Index: grub/include/grub/serial.h
===================================================================
--- grub.orig/include/grub/serial.h
+++ grub/include/grub/serial.h
@@ -210,6 +210,10 @@ grub_arcserial_init (void);
 struct grub_serial_port *grub_arcserial_add_port (const char *path);
 #endif
 
+#ifdef GRUB_HAS_PCI
+void grub_pciserial_init (void);
+#endif
+
 struct grub_serial_port *grub_serial_find (const char *name);
 extern struct grub_serial_driver grub_ns8250_driver;
 void EXPORT_FUNC(grub_serial_unregister_driver) (struct grub_serial_driver *driver);
Index: grub/docs/grub.texi
===================================================================
--- grub.orig/docs/grub.texi
+++ grub/docs/grub.texi
@@ -1386,6 +1386,7 @@ separated by spaces.
 Valid terminal input names depend on the platform, but may include
 @samp{console} (native platform console), @samp{serial} (serial terminal),
 @samp{serial_<port>} (serial terminal with explicit port selection),
+@samp{pci_<bus>:<device>.<function>} (PCI serial with explicit location),
 @samp{at_keyboard} (PC AT keyboard), or @samp{usb_keyboard} (USB keyboard
 using the HID Boot Protocol, for cases where the firmware does not handle
 this).
@@ -1399,6 +1400,7 @@ separated by spaces.
 Valid terminal output names depend on the platform, but may include
 @samp{console} (native platform console), @samp{serial} (serial terminal),
 @samp{serial_<port>} (serial terminal with explicit port selection),
+@samp{pci_<bus>:<device>.<function>} (PCI serial with explicit location),
 @samp{gfxterm} (graphics-mode output), @samp{vga_text} (VGA text output),
 @samp{mda_text} (MDA text output), @samp{morse} (Morse-coding using system
 beeper) or @samp{spkmodem} (simple data protocol using system speaker).
@@ -4165,7 +4167,7 @@ Commands usable anywhere in the menu and
 @node serial
 @subsection serial
 
-@deffn Command serial [@option{--unit=unit}] [@option{--port=port}] [@option{--speed=speed}] [@option{--word=word}] [@option{--parity=parity}] [@option{--stop=stop}]
+@deffn Command serial [@option{--unit=unit}] [@option{--port=port}] [@option{--speed=speed}] [@option{--word=word}] [@option{--parity=parity}] [@option{--stop=stop}] [@option{name}]
 Initialize a serial device. @var{unit} is a number in the range 0-3
 specifying which serial port to use; default is 0, which corresponds to
 the port often called COM1.
@@ -4197,6 +4199,19 @@ If passed no @var{unit} nor @var{port},
 the system default serial port and its configuration. If this information
 is not available, it will default to @var{unit} 0.
 
+If used @var{name}, a machine and driver specific name given during probing,
+will be used to indicate which serial port to use. Possible forms include:
+@itemize @bullet
+@item
+@samp{serial_<port>} as an alternative to --port
+@item
+@samp{usbN} the N'th USB serial detected
+@item
+@samp{efiN} the N'th EFI serial detected
+@item
+@samp{pci_<bus>:<device>.<func>} PCI serial at the specified location
+@end itemize
+
 The serial port is not used as a communication channel unless the
 @command{terminal_input} or @command{terminal_output} command is used
 (@pxref{terminal_input}, @pxref{terminal_output}).
@@ -4205,6 +4220,7 @@ Examples:
 @example
 serial --port=3f8 --speed=9600
 serial --port=mmio,fefb0000.l --speed=115200
+serial --speed=115200 pci_00:16.3
 @end example
 
 See also @ref{Serial terminal}.