clk: qcom: Add SDX55 APCS clock controller support

Add a driver for the SDX55 APCS clock controller. It is part of the APCS
hardware block, which among other things implements also a combined mux
and half integer divider functionality. The APCS clock controller has 3
parent clocks:

1. Board XO
2. Fixed rate GPLL0
3. A7 PLL

This is required for enabling CPU frequency scaling on SDX55-based
platforms.

Signed-off-by: Manivannan Sadhasivam <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
[[e-mail]: Fix unused ret in probe by hardcoding it]
Signed-off-by: Stephen Boyd <[e-mail]>

drivers/clk/qcom/Kconfig

···
 	  Say Y if you want to support CPU clock scaling using CPUfreq
 	  drivers for dynamic power management.
 
+config QCOM_CLK_APCS_SDX55
+	tristate "SDX55 APCS Clock Controller"
+	depends on QCOM_APCS_IPC || COMPILE_TEST
+	help
+	  Support for the APCS Clock Controller on SDX55 platform. The
+	  APCS is managing the mux and divider which feeds the CPUs.
+	  Say Y if you want to support CPU frequency scaling on devices
+	  such as SDX55.
+
 config QCOM_CLK_RPM
 	tristate "RPM based Clock Controller"
 	depends on MFD_QCOM_RPM

drivers/clk/qcom/Makefile

···
 obj-$(CONFIG_QCOM_A7PLL) += a7-pll.o
 obj-$(CONFIG_QCOM_CLK_APCS_MSM8916) += apcs-msm8916.o
 obj-$(CONFIG_QCOM_CLK_APCC_MSM8996) += clk-cpu-8996.o
+obj-$(CONFIG_QCOM_CLK_APCS_SDX55) += apcs-sdx55.o
 obj-$(CONFIG_QCOM_CLK_RPM) += clk-rpm.o
 obj-$(CONFIG_QCOM_CLK_RPMH) += clk-rpmh.o
 obj-$(CONFIG_QCOM_CLK_SMD_RPM) += clk-smd-rpm.o

drivers/clk/qcom/apcs-sdx55.c

···
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Qualcomm SDX55 APCS clock controller driver
+ *
+ * Copyright (c) 2020, Linaro Limited
+ * Author: Manivannan Sadhasivam <[e-mail]>
+ */
+
+#include <linux/clk.h>
+#include <linux/clk-provider.h>
+#include <linux/cpu.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/pm_domain.h>
+#include <linux/regmap.h>
+#include <linux/slab.h>
+
+#include "clk-regmap.h"
+#include "clk-regmap-mux-div.h"
+
+static const u32 apcs_mux_clk_parent_map[] = { 0, 1, 5 };
+
+static const struct clk_parent_data pdata[] = {
+	{ .fw_name = "ref" },
+	{ .fw_name = "aux" },
+	{ .fw_name = "pll" },
+};
+
+/*
+ * We use the notifier function for switching to a temporary safe configuration
+ * (mux and divider), while the A7 PLL is reconfigured.
+ */
+static int a7cc_notifier_cb(struct notifier_block *nb, unsigned long event,
+			    void *data)
+{
+	int ret = 0;
+	struct clk_regmap_mux_div *md = container_of(nb,
+						     struct clk_regmap_mux_div,
+						     clk_nb);
+	if (event == PRE_RATE_CHANGE)
+		/* set the mux and divider to safe frequency (400mhz) */
+		ret = mux_div_set_src_div(md, 1, 2);
+
+	return notifier_from_errno(ret);
+}
+
+static int qcom_apcs_sdx55_clk_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct device *parent = dev->parent;
+	struct device *cpu_dev;
+	struct clk_regmap_mux_div *a7cc;
+	struct regmap *regmap;
+	struct clk_init_data init = { };
+	int ret;
+
+	regmap = dev_get_regmap(parent, NULL);
+	if (!regmap) {
+		dev_err_probe(dev, -ENODEV, "Failed to get parent regmap\n");
+		return -ENODEV;
+	}
+
+	a7cc = devm_kzalloc(dev, sizeof(*a7cc), GFP_KERNEL);
+	if (!a7cc)
+		return -ENOMEM;
+
+	init.name = "a7mux";
+	init.parent_data = pdata;
+	init.num_parents = ARRAY_SIZE(pdata);
+	init.ops = &clk_regmap_mux_div_ops;
+
+	a7cc->clkr.hw.init = &init;
+	a7cc->clkr.regmap = regmap;
+	a7cc->reg_offset = 0x8;
+	a7cc->hid_width = 5;
+	a7cc->hid_shift = 0;
+	a7cc->src_width = 3;
+	a7cc->src_shift = 8;
+	a7cc->parent_map = apcs_mux_clk_parent_map;
+
+	a7cc->pclk = devm_clk_get(parent, "pll");
+	if (IS_ERR(a7cc->pclk)) {
+		ret = PTR_ERR(a7cc->pclk);
+		if (ret != -EPROBE_DEFER)
+			dev_err_probe(dev, ret, "Failed to get PLL clk\n");
+		return ret;
+	}
+
+	a7cc->clk_nb.notifier_call = a7cc_notifier_cb;
+	ret = clk_notifier_register(a7cc->pclk, &a7cc->clk_nb);
+	if (ret) {
+		dev_err_probe(dev, ret, "Failed to register clock notifier\n");
+		return ret;
+	}
+
+	ret = devm_clk_register_regmap(dev, &a7cc->clkr);
+	if (ret) {
+		dev_err_probe(dev, ret, "Failed to register regmap clock\n");
+		goto err;
+	}
+
+	ret = devm_of_clk_add_hw_provider(dev, of_clk_hw_simple_get,
+					  &a7cc->clkr.hw);
+	if (ret) {
+		dev_err_probe(dev, ret, "Failed to add clock provider\n");
+		goto err;
+	}
+
+	platform_set_drvdata(pdev, a7cc);
+
+	/*
+	 * Attach the power domain to cpudev. Since there is no dedicated driver
+	 * for CPUs and the SDX55 platform lacks hardware specific CPUFreq
+	 * driver, there seems to be no better place to do this. So do it here!
+	 */
+	cpu_dev = get_cpu_device(0);
+	dev_pm_domain_attach(cpu_dev, true);
+
+	return 0;
+
+err:
+	clk_notifier_unregister(a7cc->pclk, &a7cc->clk_nb);
+	return ret;
+}
+
+static int qcom_apcs_sdx55_clk_remove(struct platform_device *pdev)
+{
+	struct device *cpu_dev = get_cpu_device(0);
+	struct clk_regmap_mux_div *a7cc = platform_get_drvdata(pdev);
+
+	clk_notifier_unregister(a7cc->pclk, &a7cc->clk_nb);
+	dev_pm_domain_detach(cpu_dev, true);
+
+	return 0;
+}
+
+static struct platform_driver qcom_apcs_sdx55_clk_driver = {
+	.probe = qcom_apcs_sdx55_clk_probe,
+	.remove = qcom_apcs_sdx55_clk_remove,
+	.driver = {
+		.name = "qcom-sdx55-acps-clk",
+	},
+};
+module_platform_driver(qcom_apcs_sdx55_clk_driver);
+
+MODULE_AUTHOR("Manivannan Sadhasivam <[e-mail]>");
+MODULE_LICENSE("GPL v2");
+MODULE_DESCRIPTION("Qualcomm SDX55 APCS clock driver");