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