1// SPDX-License-Identifier: GPL-2.0
  2/*
  3 * AMD Platform Security Processor (PSP) Platform Access interface
  4 *
  5 * Copyright (C) 2023 Advanced Micro Devices, Inc.
  6 *
  7 * Author: Mario Limonciello <mario.limonciello@amd.com>
  8 *
  9 * Some of this code is adapted from drivers/i2c/busses/i2c-designware-amdpsp.c
 10 * developed by Jan Dabros <jsd@semihalf.com> and Copyright (C) 2022 Google Inc.
 11 *
 12 */
 13
 14#include <linux/bitfield.h>
 15#include <linux/errno.h>
 16#include <linux/iopoll.h>
 17#include <linux/mutex.h>
 18
 19#include "platform-access.h"
 20
 21#define PSP_CMD_TIMEOUT_US	(500 * USEC_PER_MSEC)
 22#define DOORBELL_CMDRESP_STS	GENMASK(7, 0)
 23
 24/* Recovery field should be equal 0 to start sending commands */
 25static int check_recovery(u32 __iomem *cmd)
 26{
 27	return FIELD_GET(PSP_CMDRESP_RECOVERY, ioread32(cmd));
 28}
 29
 30static int wait_cmd(u32 __iomem *cmd)
 31{
 32	u32 tmp, expected;
 33
 34	/* Expect mbox_cmd to be cleared and ready bit to be set by PSP */
 35	expected = FIELD_PREP(PSP_CMDRESP_RESP, 1);
 36
 37	/*
 38	 * Check for readiness of PSP mailbox in a tight loop in order to
 39	 * process further as soon as command was consumed.
 40	 */
 41	return readl_poll_timeout(cmd, tmp, (tmp & expected), 0,
 42				  PSP_CMD_TIMEOUT_US);
 43}
 44
 45int psp_check_platform_access_status(void)
 46{
 47	struct psp_device *psp = psp_get_master_device();
 48
 49	if (!psp || !psp->platform_access_data)
 50		return -ENODEV;
 51
 52	return 0;
 53}
 54EXPORT_SYMBOL(psp_check_platform_access_status);
 55
 56int psp_send_platform_access_msg(enum psp_platform_access_msg msg,
 57				 struct psp_request *req)
 58{
 59	struct psp_device *psp = psp_get_master_device();
 60	u32 __iomem *cmd, *lo, *hi;
 61	struct psp_platform_access_device *pa_dev;
 62	phys_addr_t req_addr;
 63	u32 cmd_reg;
 64	int ret;
 65
 66	if (!psp || !psp->platform_access_data)
 67		return -ENODEV;
 68
 69	pa_dev = psp->platform_access_data;
 70
 71	if (!pa_dev->vdata->cmdresp_reg || !pa_dev->vdata->cmdbuff_addr_lo_reg ||
 72	    !pa_dev->vdata->cmdbuff_addr_hi_reg)
 73		return -ENODEV;
 74
 75	cmd = psp->io_regs + pa_dev->vdata->cmdresp_reg;
 76	lo = psp->io_regs + pa_dev->vdata->cmdbuff_addr_lo_reg;
 77	hi = psp->io_regs + pa_dev->vdata->cmdbuff_addr_hi_reg;
 78
 79	mutex_lock(&pa_dev->mailbox_mutex);
 80
 81	if (check_recovery(cmd)) {
 82		dev_dbg(psp->dev, "platform mailbox is in recovery\n");
 83		ret = -EBUSY;
 84		goto unlock;
 85	}
 86
 87	if (wait_cmd(cmd)) {
 88		dev_dbg(psp->dev, "platform mailbox is not done processing command\n");
 89		ret = -EBUSY;
 90		goto unlock;
 91	}
 92
 93	/*
 94	 * Fill mailbox with address of command-response buffer, which will be
 95	 * used for sending i2c requests as well as reading status returned by
 96	 * PSP. Use physical address of buffer, since PSP will map this region.
 97	 */
 98	req_addr = __psp_pa(req);
 99	iowrite32(lower_32_bits(req_addr), lo);
100	iowrite32(upper_32_bits(req_addr), hi);
101
102	print_hex_dump_debug("->psp ", DUMP_PREFIX_OFFSET, 16, 2, req,
103			     req->header.payload_size, false);
104
105	/* Write command register to trigger processing */
106	cmd_reg = FIELD_PREP(PSP_CMDRESP_CMD, msg);
107	iowrite32(cmd_reg, cmd);
108
109	if (wait_cmd(cmd)) {
110		ret = -ETIMEDOUT;
111		goto unlock;
112	}
113
114	/* Ensure it was triggered by this driver */
115	if (ioread32(lo) != lower_32_bits(req_addr) ||
116	    ioread32(hi) != upper_32_bits(req_addr)) {
117		ret = -EBUSY;
118		goto unlock;
119	}
120
121	/*
122	 * Read status from PSP. If status is non-zero, it indicates an error
123	 * occurred during "processing" of the command.
124	 * If status is zero, it indicates the command was "processed"
125	 * successfully, but the result of the command is in the payload.
126	 * Return both cases to the caller as -EIO to investigate.
127	 */
128	cmd_reg = ioread32(cmd);
129	if (FIELD_GET(PSP_CMDRESP_STS, cmd_reg))
130		req->header.status = FIELD_GET(PSP_CMDRESP_STS, cmd_reg);
131	if (req->header.status) {
132		ret = -EIO;
133		goto unlock;
134	}
135
136	print_hex_dump_debug("<-psp ", DUMP_PREFIX_OFFSET, 16, 2, req,
137			     req->header.payload_size, false);
138
139	ret = 0;
140
141unlock:
142	mutex_unlock(&pa_dev->mailbox_mutex);
143
144	return ret;
145}
146EXPORT_SYMBOL_GPL(psp_send_platform_access_msg);
147
148int psp_ring_platform_doorbell(int msg, u32 *result)
149{
150	struct psp_device *psp = psp_get_master_device();
151	struct psp_platform_access_device *pa_dev;
152	u32 __iomem *button, *cmd;
153	int ret, val;
154
155	if (!psp || !psp->platform_access_data)
156		return -ENODEV;
157
158	pa_dev = psp->platform_access_data;
159	button = psp->io_regs + pa_dev->vdata->doorbell_button_reg;
160	cmd = psp->io_regs + pa_dev->vdata->doorbell_cmd_reg;
161
162	mutex_lock(&pa_dev->doorbell_mutex);
163
164	if (wait_cmd(cmd)) {
165		dev_err(psp->dev, "doorbell command not done processing\n");
166		ret = -EBUSY;
167		goto unlock;
168	}
169
170	iowrite32(FIELD_PREP(DOORBELL_CMDRESP_STS, msg), cmd);
171	iowrite32(PSP_DRBL_RING, button);
172
173	if (wait_cmd(cmd)) {
174		ret = -ETIMEDOUT;
175		goto unlock;
176	}
177
178	val = FIELD_GET(DOORBELL_CMDRESP_STS, ioread32(cmd));
179	if (val) {
180		if (result)
181			*result = val;
182		ret = -EIO;
183		goto unlock;
184	}
185
186	ret = 0;
187unlock:
188	mutex_unlock(&pa_dev->doorbell_mutex);
189
190	return ret;
191}
192EXPORT_SYMBOL_GPL(psp_ring_platform_doorbell);
193
194void platform_access_dev_destroy(struct psp_device *psp)
195{
196	struct psp_platform_access_device *pa_dev = psp->platform_access_data;
197
198	if (!pa_dev)
199		return;
200
201	mutex_destroy(&pa_dev->mailbox_mutex);
202	mutex_destroy(&pa_dev->doorbell_mutex);
203	psp->platform_access_data = NULL;
204}
205
206int platform_access_dev_init(struct psp_device *psp)
207{
208	struct device *dev = psp->dev;
209	struct psp_platform_access_device *pa_dev;
210
211	pa_dev = devm_kzalloc(dev, sizeof(*pa_dev), GFP_KERNEL);
212	if (!pa_dev)
213		return -ENOMEM;
214
215	psp->platform_access_data = pa_dev;
216	pa_dev->psp = psp;
217	pa_dev->dev = dev;
218
219	pa_dev->vdata = (struct platform_access_vdata *)psp->vdata->platform_access;
220
221	mutex_init(&pa_dev->mailbox_mutex);
222	mutex_init(&pa_dev->doorbell_mutex);
223
224	dev_dbg(dev, "platform access enabled\n");
225
226	return 0;
227}