Re: [PATCH v3 1/2] term/serial: Add support for PCI serial devices

[Daniel Kiper]

On Sat, May 13, 2023 at 02:54:51AM -0500, Glenn Washburn wrote:
> From: "peterz@infradead.org" <peterz@infradead.org>
>
> 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 --port=0x40a0 --speed=115200"
> GRUB_TERMINAL="serial console"
>
> Documentation is added to note that serial devices found on the PCI bus will
> be exposed as "pci,XX:XX.X" and how to find serial terminal logical names.
> Also, some minor documentation improvements were added.
>
> This can be tested in QEMU by adding a pci-serial device, eg. using the option
> "-device pci-serial".
>
> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
> Tested-by: Glenn Washburn <development@efficientek.com>
> Signed-off-by: Glenn Washburn <development@efficientek.com>
> ---
>  docs/grub.texi              | 13 ++++--
>  grub-core/Makefile.core.def |  1 +
>  grub-core/term/pci/serial.c | 91 +++++++++++++++++++++++++++++++++++++
>  grub-core/term/serial.c     |  6 ++-
>  include/grub/pci.h          |  5 ++
>  include/grub/serial.h       |  4 ++
>  6 files changed, 116 insertions(+), 4 deletions(-)
>  create mode 100644 grub-core/term/pci/serial.c
>
> diff --git a/docs/grub.texi b/docs/grub.texi
> index a3e9ce2d1ac7..477919ee901b 100644
> --- a/docs/grub.texi
> +++ b/docs/grub.texi
> @@ -2716,8 +2716,7 @@ grub> @kbd{terminal_input serial; terminal_output 
> serial}
>  The command @command{serial} initializes the serial unit 0 with the
>  speed 9600bps. The serial unit 0 is usually called @samp{COM1}, so, if
>  you want to use COM2, you must specify @samp{--unit=1} instead. This
> -command accepts many other options, so please refer to @ref{serial},
> -for more details.
> +command accepts many other options, @pxref{serial} for more details.
>
>  Without argument or with @samp{--port=auto}, GRUB will attempt to use
>  ACPI when available to auto-detect the default serial port and its
> @@ -4186,6 +4185,9 @@ Additionally, an MMIO address can be suffixed with:
>  @samp{.q} for 64-bit long long word access
>  @end itemize
>
> +Also, @var{port} can be of the form @samp{pci,XX:XX.X} to indicate a serial
> +device exposed on the PCI bus.
> +
>  @var{speed} is the transmission speed; default is 9600. @var{word} and
>  @var{stop} are the number of data bits and stop bits. Data bits must
>  be in the range 5-8 and stop bits must be 1 or 2. Default is 8 data
> @@ -4201,10 +4203,15 @@ 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}).
>
> +Note, valid @var{port} values, excluding IO port addresses, can be found
> +by listing terminals with @command{terminal_output}, selecting all names
> +prefixed by @samp{serial_} and removing that prefix.
> +
>  Examples:
>  @example
> -serial --port=3f8 --speed=9600
> +serial --port=0x3f8 --speed=9600
>  serial --port=mmio,fefb0000.l --speed=115200
> +serial --port=pci,00:16.3 --speed=115200
>  @end example
>
>  See also @ref{Serial terminal}.
> diff --git a/grub-core/Makefile.core.def b/grub-core/Makefile.core.def
> index 801df7c21de6..fb4cc066c526 100644
> --- a/grub-core/Makefile.core.def
> +++ b/grub-core/Makefile.core.def
> @@ -2064,6 +2064,7 @@ module = {
>    ieee1275 = term/ieee1275/serial.c;
>    mips_arc = term/arc/serial.c;
>    efi = term/efi/serial.c;
> +  x86 = term/pci/serial.c;
>
>    enable = terminfomodule;
>    enable = ieee1275;
> diff --git a/grub-core/term/pci/serial.c b/grub-core/term/pci/serial.c
> new file mode 100644
> index 000000000000..0b8fe815f5ca
> --- /dev/null
> +++ b/grub-core/term/pci/serial.c
> @@ -0,0 +1,91 @@
> +/*
> + *  GRUB  --  GRand Unified Bootloader
> + *  Copyright (C) 2023  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 compattible 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);
> +}
> diff --git a/grub-core/term/serial.c b/grub-core/term/serial.c
> index c65ffc63cecb..05db4cf177c2 100644
> --- a/grub-core/term/serial.c
> +++ b/grub-core/term/serial.c
> @@ -255,7 +255,8 @@ grub_cmd_serial (grub_extcmd_context_t ctxt, int argc, 
> char **args)
>
>    if (state[OPTION_PORT].set)
>      {
> -      if (grub_strncmp (state[OPTION_PORT].arg, "mmio,", sizeof ("mmio,") - 
> 1) == 0)
> +      if (grub_strncmp (state[OPTION_PORT].arg, "mmio,", sizeof ("mmio,") - 
> 1) == 0 ||
> +       grub_strncmp (state[OPTION_PORT].arg, "pci,", sizeof ("pci,") - 1) == 
> 0)
>            grub_snprintf (pname, sizeof (pname), "%s", state[1].arg);
>        else
>            grub_snprintf (pname, sizeof (pname), "port%lx",
> @@ -505,6 +506,9 @@ GRUB_MOD_INIT(serial)
>  #ifdef GRUB_MACHINE_ARC
>    grub_arcserial_init ();
>  #endif
> +#ifdef GRUB_HAS_PCI

I think this...

> +  grub_pciserial_init ();
> +#endif
>  }
>
>  GRUB_MOD_FINI(serial)
> diff --git a/include/grub/pci.h b/include/grub/pci.h
> index 262c89b748bb..b228bb1b71fd 100644
> --- a/include/grub/pci.h
> +++ b/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
>
> diff --git a/include/grub/serial.h b/include/grub/serial.h
> index a955c076d892..9226d51f5831 100644
> --- a/include/grub/serial.h
> +++ b/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

... and this should be changed to

  #if defined(__i386__) && defined(__x86_64__)

Otherwise Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>...

I can do the changes mentioned above before push.

Peter, Glenn, thank you for adding this feature.

> +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);

Daniel