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"
Signed-off-by: Peter Zijlstra (Intel) <pet...@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;
enable = terminfomodule;
enable = ieee1275;
Index: grub/grub-core/term/pci/serial.c
===================================================================
--- /dev/null
+++ grub/grub-core/term/pci/serial.c
@@ -0,0 +1,95 @@
+/*
+ * 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, void *data)
+{
+ 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;
+
+ 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%d", (*port_num));
+ if (port->name == NULL)
+ goto error;
+
+ 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 error;
+ }
+
+ err = grub_serial_register (port);
+ if (err != GRUB_ERR_NONE)
+ goto error;
+
+ (*port_num)++;
+
+ return 0;
+
+error:
+ grub_free (port->name);
+ grub_free (port);
+ return 0;
+}
+
+void
+grub_pciserial_init (void)
+{
+ int port_num;
+
+ grub_pci_iterate (find_pciserial, &port_num);
+}
Index: grub/grub-core/term/serial.c
===================================================================
--- grub.orig/grub-core/term/serial.c
+++ grub/grub-core/term/serial.c
@@ -448,6 +448,9 @@ 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
@@ -193,6 +193,10 @@ const char *
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);
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