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// SPDX-License-Identifier: GPL-2.0+
/*
* (C) Copyright 2022 Microsoft Corporation <www.microsoft.com>
* Stephen Carlson <stcarlso@linux.microsoft.com>
*
* PCI Express Maximum Packet Size (MPS) configuration
*/
#include <common.h>
#include <bootretry.h>
#include <cli.h>
#include <command.h>
#include <console.h>
#include <dm.h>
#include <init.h>
#include <asm/processor.h>
#include <asm/io.h>
#include <pci.h>
#define PCI_MPS_SAFE 0
#define PCI_MPS_PEER2PEER 1
static int pci_mps_find_safe(struct udevice *bus, unsigned int *min_mps,
unsigned int *n)
{
struct udevice *dev;
int res = 0, addr;
unsigned int mpss;
u32 regval;
if (!min_mps || !n)
return -EINVAL;
for (device_find_first_child(bus, &dev);
dev;
device_find_next_child(&dev)) {
addr = dm_pci_find_capability(dev, PCI_CAP_ID_EXP);
if (addr <= 0)
continue;
res = dm_pci_read_config32(dev, addr + PCI_EXP_DEVCAP,
®val);
if (res != 0)
return res;
mpss = (unsigned int)(regval & PCI_EXP_DEVCAP_PAYLOAD);
*n += 1;
if (mpss < *min_mps)
*min_mps = mpss;
}
return res;
}
static int pci_mps_set_bus(struct udevice *bus, unsigned int target)
{
struct udevice *dev;
u32 mpss, target_mps = (u32)(target << 5);
u16 mps;
int res = 0, addr;
for (device_find_first_child(bus, &dev);
dev && res == 0;
device_find_next_child(&dev)) {
addr = dm_pci_find_capability(dev, PCI_CAP_ID_EXP);
if (addr <= 0)
continue;
res = dm_pci_read_config32(dev, addr + PCI_EXP_DEVCAP,
&mpss);
if (res != 0)
return res;
/* Do not set device above its maximum MPSS */
mpss = (mpss & PCI_EXP_DEVCAP_PAYLOAD) << 5;
if (target_mps < mpss)
mps = (u16)target_mps;
else
mps = (u16)mpss;
res = dm_pci_clrset_config16(dev, addr + PCI_EXP_DEVCTL,
PCI_EXP_DEVCTL_PAYLOAD, mps);
}
return res;
}
/*
* Sets the MPS of each PCI Express device to the specified policy.
*/
static int pci_mps_set(int policy)
{
struct udevice *bus;
int i, res = 0;
/* 0 = 128B, min value for hotplug */
unsigned int mps = 0;
if (policy == PCI_MPS_SAFE) {
unsigned int min_mps = PCI_EXP_DEVCAP_PAYLOAD_4096B, n = 0;
/* Find maximum MPS supported by all devices */
for (i = 0;
uclass_get_device_by_seq(UCLASS_PCI, i, &bus) == 0 &&
res == 0;
i++)
res = pci_mps_find_safe(bus, &min_mps, &n);
/* If no devices were found, do not reconfigure */
if (n == 0)
return res;
mps = min_mps;
}
/* This message is checked by the sandbox test */
printf("Setting MPS of all devices to %uB\n", 128U << mps);
for (i = 0;
uclass_get_device_by_seq(UCLASS_PCI, i, &bus) == 0 && res == 0;
i++)
res = pci_mps_set_bus(bus, mps);
return res;
}
/*
* PCI MPS tuning commands
*
* Syntax:
* pci_mps safe
* pci_mps peer2peer
*/
static int do_pci_mps(struct cmd_tbl *cmdtp, int flag, int argc, char *const argv[])
{
char cmd = 'u';
int ret = 0;
if (argc > 1)
cmd = argv[1][0];
switch (cmd) {
case 's': /* safe */
ret = pci_mps_set(PCI_MPS_SAFE);
break;
case 'p': /* peer2peer/hotplug */
ret = pci_mps_set(PCI_MPS_PEER2PEER);
break;
default: /* usage, help */
goto usage;
}
return ret;
usage:
return CMD_RET_USAGE;
}
/***************************************************/
#ifdef CONFIG_SYS_LONGHELP
static char pci_mps_help_text[] =
"safe\n"
" - Set PCI Express MPS of all devices to safe values\n"
"pci_mps peer2peer\n"
" - Set PCI Express MPS of all devices to support hotplug and peer-to-peer DMA\n";
#endif
U_BOOT_CMD(pci_mps, 2, 0, do_pci_mps,
"configure PCI Express MPS", pci_mps_help_text);
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