diff options
| -rw-r--r-- | src/northbridge/intel/haswell/Kconfig | 9 | ||||
| -rw-r--r-- | src/northbridge/intel/haswell/early_init.c | 23 |
2 files changed, 26 insertions, 6 deletions
diff --git a/src/northbridge/intel/haswell/Kconfig b/src/northbridge/intel/haswell/Kconfig index 84be33df4e..04ab373ce2 100644 --- a/src/northbridge/intel/haswell/Kconfig +++ b/src/northbridge/intel/haswell/Kconfig @@ -78,6 +78,15 @@ config MRC_FILE The path and filename of the file to use as System Agent binary. +config HASWELL_HIDE_PEG_FROM_MRC + bool "Hide PEG devices from MRC to work around hardcoded MRC behavior" + default y + help + If set, hides all PEG devices from MRC. This allows the iGPU + to be used even when a dedicated graphics card is present. + However, it prevents MRC from programming PEG AFE registers, + which can make PEG devices unstable. When unsure, choose N. + config PRE_GRAPHICS_DELAY int "Graphics initialization delay in ms" default 0 diff --git a/src/northbridge/intel/haswell/early_init.c b/src/northbridge/intel/haswell/early_init.c index 9db6a9d0de..79cc27724c 100644 --- a/src/northbridge/intel/haswell/early_init.c +++ b/src/northbridge/intel/haswell/early_init.c @@ -84,13 +84,24 @@ static void start_peg2_link_training(const pci_devfn_t dev) printk(BIOS_DEBUG, "Started PEG1%d link training.\n", PCI_FUNC(PCI_DEV2DEVFN(dev))); /* - * Hide the PEG device while the MRC runs. This is because the MRC makes - * configurations that are not ideal if it sees a VGA device in a PEG slot, - * and it locks registers preventing changes to these configurations. + * The MRC will perform PCI enumeration, and if it detects a VGA + * device in a PEG slot, it will disable the IGD and not reserve + * any memory for it. Since the memory map is locked by the time + * MRC finishes, the IGD can't be enabled afterwards. Wonderful. + * + * If one really wants to enable the Intel iGPU as primary, hide + * all PEG devices during MRC execution. This will trick the MRC + * into thinking there aren't any, and will enable the IGD. Note + * that PEG AFE settings will not be programmed, which may cause + * stability problems at higher PCIe link speeds. The most ideal + * way to fix this problem for good is to implement native init. */ - pci_update_config32(HOST_BRIDGE, DEVEN, ~mask, 0); - peg_hidden[PCI_FUNC(PCI_DEV2DEVFN(dev))] = true; - printk(BIOS_DEBUG, "Temporarily hiding PEG1%d.\n", PCI_FUNC(PCI_DEV2DEVFN(dev))); + if (CONFIG(HASWELL_HIDE_PEG_FROM_MRC)) { + pci_update_config32(HOST_BRIDGE, DEVEN, ~mask, 0); + peg_hidden[PCI_FUNC(PCI_DEV2DEVFN(dev))] = true; + printk(BIOS_DEBUG, "Temporarily hiding PEG1%d.\n", + PCI_FUNC(PCI_DEV2DEVFN(dev))); + } } void haswell_unhide_peg(void) |