1 // SPDX-License-Identifier: GPL-2.0+
3 * Copyright (C) 2014, Bin Meng <bmeng.cn@gmail.com>
8 #include <dm/device-internal.h>
13 #include <asm/arch/device.h>
14 #include <asm/arch/tnc.h>
15 #include <asm/fsp/fsp_support.h>
16 #include <asm/processor.h>
18 static int __maybe_unused disable_igd(void)
20 struct udevice *igd, *sdvo;
23 ret = dm_pci_bus_find_bdf(TNC_IGD, &igd);
29 ret = dm_pci_bus_find_bdf(TNC_SDVO, &sdvo);
36 * According to Atom E6xx datasheet, setting VGA Disable (bit17)
37 * of Graphics Controller register (offset 0x50) prevents IGD
38 * (D2:F0) from reporting itself as a VGA display controller
39 * class in the PCI configuration space, and should also prevent
40 * it from responding to VGA legacy memory range and I/O addresses.
42 * However test result shows that with just VGA Disable bit set and
43 * a PCIe graphics card connected to one of the PCIe controllers on
44 * the E6xx, accessing the VGA legacy space still causes system hang.
45 * After a number of attempts, it turns out besides VGA Disable bit,
46 * the SDVO (D3:F0) device should be disabled to make it work.
48 * To simplify, use the Function Disable register (offset 0xc4)
49 * to disable both IGD (D2:F0) and SDVO (D3:F0) devices. Now these
50 * two devices will be completely disabled (invisible in the PCI
51 * configuration space) unless a system reset is performed.
53 dm_pci_write_config32(igd, IGD_FD, FUNC_DISABLE);
54 dm_pci_write_config32(sdvo, IGD_FD, FUNC_DISABLE);
57 * After setting the function disable bit, IGD and SDVO devices will
58 * disappear in the PCI configuration space. This however creates an
59 * inconsistent state from a driver model PCI controller point of view,
60 * as these two PCI devices are still attached to its parent's child
61 * device list as maintained by the driver model. Some driver model PCI
62 * APIs like dm_pci_find_class(), are referring to the list to speed up
63 * the finding process instead of re-enumerating the whole PCI bus, so
64 * it gets the stale cached data which is wrong.
66 * Note x86 PCI enueration normally happens twice, in pre-relocation
67 * phase and post-relocation. One option might be to call disable_igd()
68 * in one of the pre-relocation initialization hooks so that it gets
69 * disabled in the first round, and when it comes to the second round
70 * driver model PCI will construct a correct list. Unfortunately this
71 * does not work as Intel FSP is used on this platform to perform low
72 * level initialization, and fsp_init_phase_pci() is called only once
73 * in the post-relocation phase. If we disable IGD and SDVO devices,
74 * fsp_init_phase_pci() simply hangs and never returns.
76 * So the only option we have is to manually remove these two devices.
78 ret = device_remove(igd, DM_REMOVE_NORMAL);
81 ret = device_unbind(igd);
84 ret = device_remove(sdvo, DM_REMOVE_NORMAL);
87 ret = device_unbind(sdvo);
94 int arch_cpu_init(void)
96 post_code(POST_CPU_INIT);
98 return x86_cpu_init_f();
101 int arch_early_init_r(void)
105 #ifdef CONFIG_DISABLE_IGD