// SPDX-License-Identifier: GPL-2.0
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/*
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* PCI-related functions used by the EFI stub on multiple
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* architectures.
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*
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* Copyright 2019 Google, LLC
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*/
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#include <linux/efi.h>
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#include <linux/pci.h>
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#include <asm/efi.h>
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#include "efistub.h"
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void efi_pci_disable_bridge_busmaster(void)
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{
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efi_guid_t pci_proto = EFI_PCI_IO_PROTOCOL_GUID;
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unsigned long pci_handle_size = 0;
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efi_handle_t *pci_handle = NULL;
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efi_handle_t handle;
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efi_status_t status;
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u16 class, command;
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int i;
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status = efi_bs_call(locate_handle, EFI_LOCATE_BY_PROTOCOL, &pci_proto,
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NULL, &pci_handle_size, NULL);
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if (status != EFI_BUFFER_TOO_SMALL) {
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if (status != EFI_SUCCESS && status != EFI_NOT_FOUND)
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efi_err("Failed to locate PCI I/O handles'\n");
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return;
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}
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status = efi_bs_call(allocate_pool, EFI_LOADER_DATA, pci_handle_size,
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(void **)&pci_handle);
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if (status != EFI_SUCCESS) {
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efi_err("Failed to allocate memory for 'pci_handle'\n");
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return;
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}
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status = efi_bs_call(locate_handle, EFI_LOCATE_BY_PROTOCOL, &pci_proto,
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NULL, &pci_handle_size, pci_handle);
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if (status != EFI_SUCCESS) {
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efi_err("Failed to locate PCI I/O handles'\n");
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goto free_handle;
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}
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for_each_efi_handle(handle, pci_handle, pci_handle_size, i) {
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efi_pci_io_protocol_t *pci;
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unsigned long segment_nr, bus_nr, device_nr, func_nr;
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status = efi_bs_call(handle_protocol, handle, &pci_proto,
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(void **)&pci);
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if (status != EFI_SUCCESS)
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continue;
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/*
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* Disregard devices living on bus 0 - these are not behind a
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* bridge so no point in disconnecting them from their drivers.
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*/
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status = efi_call_proto(pci, get_location, &segment_nr, &bus_nr,
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&device_nr, &func_nr);
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if (status != EFI_SUCCESS || bus_nr == 0)
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continue;
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/*
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* Don't disconnect VGA controllers so we don't risk losing
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* access to the framebuffer. Drivers for true PCIe graphics
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* controllers that are behind a PCIe root port do not use
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* DMA to implement the GOP framebuffer anyway [although they
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* may use it in their implementation of Gop->Blt()], and so
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* disabling DMA in the PCI bridge should not interfere with
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* normal operation of the device.
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*/
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status = efi_call_proto(pci, pci.read, EfiPciIoWidthUint16,
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PCI_CLASS_DEVICE, 1, &class);
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if (status != EFI_SUCCESS || class == PCI_CLASS_DISPLAY_VGA)
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continue;
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/* Disconnect this handle from all its drivers */
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efi_bs_call(disconnect_controller, handle, NULL, NULL);
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}
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for_each_efi_handle(handle, pci_handle, pci_handle_size, i) {
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efi_pci_io_protocol_t *pci;
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status = efi_bs_call(handle_protocol, handle, &pci_proto,
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(void **)&pci);
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if (status != EFI_SUCCESS || !pci)
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continue;
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status = efi_call_proto(pci, pci.read, EfiPciIoWidthUint16,
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PCI_CLASS_DEVICE, 1, &class);
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if (status != EFI_SUCCESS || class != PCI_CLASS_BRIDGE_PCI)
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continue;
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/* Disable busmastering */
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status = efi_call_proto(pci, pci.read, EfiPciIoWidthUint16,
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PCI_COMMAND, 1, &command);
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if (status != EFI_SUCCESS || !(command & PCI_COMMAND_MASTER))
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continue;
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command &= ~PCI_COMMAND_MASTER;
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status = efi_call_proto(pci, pci.write, EfiPciIoWidthUint16,
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PCI_COMMAND, 1, &command);
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if (status != EFI_SUCCESS)
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efi_err("Failed to disable PCI busmastering\n");
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}
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free_handle:
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efi_bs_call(free_pool, pci_handle);
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}
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