1// SPDX-License-Identifier: GPL-2.0+
2/*
3 * (C) Copyright 2022 Microsoft Corporation <www.microsoft.com>
4 * Stephen Carlson <stcarlso@linux.microsoft.com>
5 *
6 * PCI Express Maximum Packet Size (MPS) configuration
7 */
8
9#include <common.h>
10#include <bootretry.h>
11#include <cli.h>
12#include <command.h>
13#include <console.h>
14#include <dm.h>
15#include <init.h>
16#include <asm/processor.h>
17#include <asm/io.h>
18#include <pci.h>
19
20#define PCI_MPS_SAFE 0
21#define PCI_MPS_PEER2PEER 1
22
23static int pci_mps_find_safe(struct udevice *bus, unsigned int *min_mps,
24			     unsigned int *n)
25{
26	struct udevice *dev;
27	int res = 0, addr;
28	unsigned int mpss;
29	u32 regval;
30
31	if (!min_mps || !n)
32		return -EINVAL;
33
34	for (device_find_first_child(bus, &dev);
35	     dev;
36	     device_find_next_child(&dev)) {
37		addr = dm_pci_find_capability(dev, PCI_CAP_ID_EXP);
38		if (addr <= 0)
39			continue;
40
41		res = dm_pci_read_config32(dev, addr + PCI_EXP_DEVCAP,
42					   &regval);
43		if (res != 0)
44			return res;
45		mpss = (unsigned int)(regval & PCI_EXP_DEVCAP_PAYLOAD);
46		*n += 1;
47		if (mpss < *min_mps)
48			*min_mps = mpss;
49	}
50
51	return res;
52}
53
54static int pci_mps_set_bus(struct udevice *bus, unsigned int target)
55{
56	struct udevice *dev;
57	u32 mpss, target_mps = (u32)(target << 5);
58	u16 mps;
59	int res = 0, addr;
60
61	for (device_find_first_child(bus, &dev);
62	     dev && res == 0;
63	     device_find_next_child(&dev)) {
64		addr = dm_pci_find_capability(dev, PCI_CAP_ID_EXP);
65		if (addr <= 0)
66			continue;
67
68		res = dm_pci_read_config32(dev, addr + PCI_EXP_DEVCAP,
69					   &mpss);
70		if (res != 0)
71			return res;
72
73		/* Do not set device above its maximum MPSS */
74		mpss = (mpss & PCI_EXP_DEVCAP_PAYLOAD) << 5;
75		if (target_mps < mpss)
76			mps = (u16)target_mps;
77		else
78			mps = (u16)mpss;
79		res = dm_pci_clrset_config16(dev, addr + PCI_EXP_DEVCTL,
80					     PCI_EXP_DEVCTL_PAYLOAD, mps);
81	}
82
83	return res;
84}
85
86/*
87 * Sets the MPS of each PCI Express device to the specified policy.
88 */
89static int pci_mps_set(int policy)
90{
91	struct udevice *bus;
92	int i, res = 0;
93	/* 0 = 128B, min value for hotplug */
94	unsigned int mps = 0;
95
96	if (policy == PCI_MPS_SAFE) {
97		unsigned int min_mps = PCI_EXP_DEVCAP_PAYLOAD_4096B, n = 0;
98
99		/* Find maximum MPS supported by all devices */
100		for (i = 0;
101		     uclass_get_device_by_seq(UCLASS_PCI, i, &bus) == 0 &&
102		     res == 0;
103		     i++)
104			res = pci_mps_find_safe(bus, &min_mps, &n);
105
106		/* If no devices were found, do not reconfigure */
107		if (n == 0)
108			return res;
109		mps = min_mps;
110	}
111
112	/* This message is checked by the sandbox test */
113	printf("Setting MPS of all devices to %uB\n", 128U << mps);
114	for (i = 0;
115	     uclass_get_device_by_seq(UCLASS_PCI, i, &bus) == 0 && res == 0;
116	     i++)
117		res = pci_mps_set_bus(bus, mps);
118
119	return res;
120}
121
122/*
123 * PCI MPS tuning commands
124 *
125 * Syntax:
126 *	pci_mps safe
127 *	pci_mps peer2peer
128 */
129static int do_pci_mps(struct cmd_tbl *cmdtp, int flag, int argc, char *const argv[])
130{
131	char cmd = 'u';
132	int ret = 0;
133
134	if (argc > 1)
135		cmd = argv[1][0];
136
137	switch (cmd) {
138	case 's':		/* safe */
139		ret = pci_mps_set(PCI_MPS_SAFE);
140		break;
141	case 'p':		/* peer2peer/hotplug */
142		ret = pci_mps_set(PCI_MPS_PEER2PEER);
143		break;
144	default:		/* usage, help */
145		goto usage;
146	}
147
148	return ret;
149usage:
150	return CMD_RET_USAGE;
151}
152
153/***************************************************/
154
155U_BOOT_LONGHELP(pci_mps,
156	"safe\n"
157	"    - Set PCI Express MPS of all devices to safe values\n"
158	"pci_mps peer2peer\n"
159	"    - Set PCI Express MPS of all devices to support hotplug and peer-to-peer DMA\n");
160
161U_BOOT_CMD(pci_mps, 2, 0, do_pci_mps,
162	   "configure PCI Express MPS", pci_mps_help_text);
163