1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3  * Voltage regulators coupler for MediaTek SoCs
4  *
5  * Copyright (C) 2022 Collabora, Ltd.
6  * Author: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
7  */
8 
9 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
10 
11 #include <linux/init.h>
12 #include <linux/kernel.h>
13 #include <linux/of.h>
14 #include <linux/regulator/coupler.h>
15 #include <linux/regulator/driver.h>
16 #include <linux/regulator/machine.h>
17 #include <linux/suspend.h>
18 
19 #define to_mediatek_coupler(x)	container_of(x, struct mediatek_regulator_coupler, coupler)
20 
21 struct mediatek_regulator_coupler {
22 	struct regulator_coupler coupler;
23 	struct regulator_dev *vsram_rdev;
24 };
25 
26 /*
27  * We currently support only couples of not more than two vregs and
28  * modify the vsram voltage only when changing voltage of vgpu.
29  *
30  * This function is limited to the GPU<->SRAM voltages relationships.
31  */
32 static int mediatek_regulator_balance_voltage(struct regulator_coupler *coupler,
33 					      struct regulator_dev *rdev,
34 					      suspend_state_t state)
35 {
36 	struct mediatek_regulator_coupler *mrc = to_mediatek_coupler(coupler);
37 	int max_spread = rdev->constraints->max_spread[0];
38 	int vsram_min_uV = mrc->vsram_rdev->constraints->min_uV;
39 	int vsram_max_uV = mrc->vsram_rdev->constraints->max_uV;
40 	int vsram_target_min_uV, vsram_target_max_uV;
41 	int min_uV = 0;
42 	int max_uV = INT_MAX;
43 	int ret;
44 
45 	/*
46 	 * If the target device is on, setting the SRAM voltage directly
47 	 * is not supported as it scales through its coupled supply voltage.
48 	 *
49 	 * An exception is made in case the use_count is zero: this means
50 	 * that this is the first time we power up the SRAM regulator, which
51 	 * implies that the target device has yet to perform initialization
52 	 * and setting a voltage at that time is harmless.
53 	 */
54 	if (rdev == mrc->vsram_rdev) {
55 		if (rdev->use_count == 0)
56 			return regulator_do_balance_voltage(rdev, state, true);
57 
58 		return -EPERM;
59 	}
60 
61 	ret = regulator_check_consumers(rdev, &min_uV, &max_uV, state);
62 	if (ret < 0)
63 		return ret;
64 
65 	if (min_uV == 0) {
66 		ret = regulator_get_voltage_rdev(rdev);
67 		if (ret < 0)
68 			return ret;
69 		min_uV = ret;
70 	}
71 
72 	ret = regulator_check_voltage(rdev, &min_uV, &max_uV);
73 	if (ret < 0)
74 		return ret;
75 
76 	/*
77 	 * If we're asked to set a voltage less than VSRAM min_uV, set
78 	 * the minimum allowed voltage on VSRAM, as in this case it is
79 	 * safe to ignore the max_spread parameter.
80 	 */
81 	vsram_target_min_uV = max(vsram_min_uV, min_uV + max_spread);
82 	vsram_target_max_uV = min(vsram_max_uV, vsram_target_min_uV + max_spread);
83 
84 	/* Make sure we're not out of range */
85 	vsram_target_min_uV = min(vsram_target_min_uV, vsram_max_uV);
86 
87 	pr_debug("Setting voltage %d-%duV on %s (minuV %d)\n",
88 		 vsram_target_min_uV, vsram_target_max_uV,
89 		 rdev_get_name(mrc->vsram_rdev), min_uV);
90 
91 	ret = regulator_set_voltage_rdev(mrc->vsram_rdev, vsram_target_min_uV,
92 					 vsram_target_max_uV, state);
93 	if (ret)
94 		return ret;
95 
96 	/* The sram voltage is now balanced: update the target vreg voltage */
97 	return regulator_do_balance_voltage(rdev, state, true);
98 }
99 
100 static int mediatek_regulator_attach(struct regulator_coupler *coupler,
101 				     struct regulator_dev *rdev)
102 {
103 	struct mediatek_regulator_coupler *mrc = to_mediatek_coupler(coupler);
104 	const char *rdev_name = rdev_get_name(rdev);
105 
106 	/*
107 	 * If we're getting a coupling of more than two regulators here and
108 	 * this means that this is surely not a GPU<->SRAM couple: in that
109 	 * case, we may want to use another coupler implementation, if any,
110 	 * or the generic one: the regulator core will keep walking through
111 	 * the list of couplers when any .attach_regulator() cb returns 1.
112 	 */
113 	if (rdev->coupling_desc.n_coupled > 2)
114 		return 1;
115 
116 	if (strstr(rdev_name, "sram")) {
117 		if (mrc->vsram_rdev)
118 			return -EINVAL;
119 		mrc->vsram_rdev = rdev;
120 	} else if (!strstr(rdev_name, "vgpu") && !strstr(rdev_name, "Vgpu")) {
121 		return 1;
122 	}
123 
124 	return 0;
125 }
126 
127 static int mediatek_regulator_detach(struct regulator_coupler *coupler,
128 				     struct regulator_dev *rdev)
129 {
130 	struct mediatek_regulator_coupler *mrc = to_mediatek_coupler(coupler);
131 
132 	if (rdev == mrc->vsram_rdev)
133 		mrc->vsram_rdev = NULL;
134 
135 	return 0;
136 }
137 
138 static struct mediatek_regulator_coupler mediatek_coupler = {
139 	.coupler = {
140 		.attach_regulator = mediatek_regulator_attach,
141 		.detach_regulator = mediatek_regulator_detach,
142 		.balance_voltage = mediatek_regulator_balance_voltage,
143 	},
144 };
145 
146 static int mediatek_regulator_coupler_init(void)
147 {
148 	if (!of_machine_is_compatible("mediatek,mt8183") &&
149 	    !of_machine_is_compatible("mediatek,mt8186") &&
150 	    !of_machine_is_compatible("mediatek,mt8192"))
151 		return 0;
152 
153 	return regulator_coupler_register(&mediatek_coupler.coupler);
154 }
155 arch_initcall(mediatek_regulator_coupler_init);
156 
157 MODULE_AUTHOR("AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>");
158 MODULE_DESCRIPTION("MediaTek Regulator Coupler driver");
159 MODULE_LICENSE("GPL");
160