1 // SPDX-License-Identifier: GPL-2.0
3 * Qualcomm APCS clock controller driver
5 * Copyright (c) 2022, Linaro Limited
6 * Author: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
9 #include <linux/bits.h>
10 #include <linux/clk-provider.h>
11 #include <linux/delay.h>
12 #include <linux/module.h>
13 #include <linux/platform_device.h>
14 #include <linux/regmap.h>
16 #define APCS_AUX_OFFSET 0x50
18 #define APCS_AUX_DIV_MASK GENMASK(17, 16)
19 #define APCS_AUX_DIV_2 0x1
21 static int qcom_apcs_msm8996_clk_probe(struct platform_device *pdev)
23 struct device *dev = &pdev->dev;
24 struct device *parent = dev->parent;
25 struct regmap *regmap;
30 regmap = dev_get_regmap(parent, NULL);
32 dev_err(dev, "failed to get regmap: %d\n", ret);
36 regmap_read(regmap, APCS_AUX_OFFSET, &val);
37 regmap_update_bits(regmap, APCS_AUX_OFFSET, APCS_AUX_DIV_MASK,
38 FIELD_PREP(APCS_AUX_DIV_MASK, APCS_AUX_DIV_2));
41 * This clock is used during CPU cluster setup while setting up CPU PLLs.
42 * Add hardware mandated delay to make sure that the sys_apcs_aux clock
43 * is stable (after setting the divider) before continuing
44 * bootstrapping to keep CPUs from ending up in a weird state.
49 * As this clocks is a parent of the CPU cluster clocks and is actually
50 * used as a parent during CPU clocks setup, we want for it to register
51 * as early as possible, without letting fw_devlink to delay probing of
52 * either of the drivers.
54 * The sys_apcs_aux is a child (divider) of gpll0, but we register it
55 * as a fixed rate clock instead to ease bootstrapping procedure. By
56 * doing this we make sure that CPU cluster clocks are able to be setup
57 * early during the boot process (as it is recommended by Qualcomm).
59 hw = devm_clk_hw_register_fixed_rate(dev, "sys_apcs_aux", NULL, 0, 300000000);
63 return devm_of_clk_add_hw_provider(dev, of_clk_hw_simple_get, hw);
66 static struct platform_driver qcom_apcs_msm8996_clk_driver = {
67 .probe = qcom_apcs_msm8996_clk_probe,
69 .name = "qcom-apcs-msm8996-clk",
73 /* Register early enough to fix the clock to be used for other cores */
74 static int __init qcom_apcs_msm8996_clk_init(void)
76 return platform_driver_register(&qcom_apcs_msm8996_clk_driver);
78 postcore_initcall(qcom_apcs_msm8996_clk_init);
80 static void __exit qcom_apcs_msm8996_clk_exit(void)
82 platform_driver_unregister(&qcom_apcs_msm8996_clk_driver);
84 module_exit(qcom_apcs_msm8996_clk_exit);
86 MODULE_AUTHOR("Dmitry Baryshkov <dmitry.baryshkov@linaro.org>");
87 MODULE_LICENSE("GPL");
88 MODULE_DESCRIPTION("Qualcomm MSM8996 APCS clock driver");