clk: qcom: add msm8996 Core Bus Framework (CBF) support

Add CBF clock driver as a part of MSM8996 CPU clocks. Significantly
based on AngeloGioacchino del Regno's work at [1].

The CBF is an interconnect between two CPU clusters, setting it up
properly is required for booting the MSM8996 with all four cores
enabled.

[1] https://github.com/sonyxperiadev/kernel/blob/aosp/LE.UM.2.3.2.r1.4/drivers/clk/qcom/clk-cpu-8996.c

Co-developed-by: Konrad Dybcio <[e-mail]>
Signed-off-by: Konrad Dybcio <[e-mail]>
Signed-off-by: Dmitry Baryshkov <[e-mail]>
[bjorn: Dropped partially uninitialized variable "ret" from cbf_clk_notifier_cb()]
Signed-off-by: Bjorn Andersson <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]

drivers/clk/qcom/Makefile

···
 obj-$(CONFIG_QCOM_A53PLL) += a53-pll.o
 obj-$(CONFIG_QCOM_A7PLL) += a7-pll.o
 obj-$(CONFIG_QCOM_CLK_APCS_MSM8916) += apcs-msm8916.o
-obj-$(CONFIG_QCOM_CLK_APCC_MSM8996) += apcs-msm8996.o clk-cpu-8996.o
+obj-$(CONFIG_QCOM_CLK_APCC_MSM8996) += apcs-msm8996.o clk-cpu-8996.o clk-cbf-8996.o
 obj-$(CONFIG_QCOM_CLK_APCS_SDX55) += apcs-sdx55.o
 obj-$(CONFIG_QCOM_CLK_RPM) += clk-rpm.o
 obj-$(CONFIG_QCOM_CLK_RPMH) += clk-rpmh.o

drivers/clk/qcom/clk-cbf-8996.c

···
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (c) 2022, 2023 Linaro Ltd.
+ */
+#include <linux/bitfield.h>
+#include <linux/clk.h>
+#include <linux/clk-provider.h>
+#include <linux/of.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/regmap.h>
+
+#include "clk-alpha-pll.h"
+#include "clk-regmap.h"
+
+/* Need to match the order of clocks in DT binding */
+enum {
+	DT_XO,
+	DT_APCS_AUX,
+};
+
+enum {
+	CBF_XO_INDEX,
+	CBF_PLL_INDEX,
+	CBF_DIV_INDEX,
+	CBF_APCS_AUX_INDEX,
+};
+
+#define DIV_THRESHOLD		600000000
+
+#define CBF_MUX_OFFSET		0x18
+#define CBF_MUX_PARENT_MASK		GENMASK(1, 0)
+#define CBF_MUX_AUTO_CLK_SEL_ALWAYS_ON_MASK GENMASK(5, 4)
+#define CBF_MUX_AUTO_CLK_SEL_ALWAYS_ON_GPLL0_SEL \
+	FIELD_PREP(CBF_MUX_AUTO_CLK_SEL_ALWAYS_ON_MASK, 0x03)
+#define CBF_MUX_AUTO_CLK_SEL_BIT	BIT(6)
+
+#define CBF_PLL_OFFSET 0xf000
+
+static const u8 cbf_pll_regs[PLL_OFF_MAX_REGS] = {
+	[PLL_OFF_L_VAL] = 0x08,
+	[PLL_OFF_ALPHA_VAL] = 0x10,
+	[PLL_OFF_USER_CTL] = 0x18,
+	[PLL_OFF_CONFIG_CTL] = 0x20,
+	[PLL_OFF_CONFIG_CTL_U] = 0x24,
+	[PLL_OFF_TEST_CTL] = 0x30,
+	[PLL_OFF_TEST_CTL_U] = 0x34,
+	[PLL_OFF_STATUS] = 0x28,
+};
+
+static const struct alpha_pll_config cbfpll_config = {
+	.l = 72,
+	.config_ctl_val = 0x200d4828,
+	.config_ctl_hi_val = 0x006,
+	.test_ctl_val = 0x1c000000,
+	.test_ctl_hi_val = 0x00004000,
+	.pre_div_mask = BIT(12),
+	.post_div_mask = 0x3 << 8,
+	.post_div_val = 0x1 << 8,
+	.main_output_mask = BIT(0),
+	.early_output_mask = BIT(3),
+};
+
+static struct clk_alpha_pll cbf_pll = {
+	.offset = CBF_PLL_OFFSET,
+	.regs = cbf_pll_regs,
+	.flags = SUPPORTS_DYNAMIC_UPDATE | SUPPORTS_FSM_MODE,
+	.clkr.hw.init = &(struct clk_init_data){
+		.name = "cbf_pll",
+		.parent_data = (const struct clk_parent_data[]) {
+			{ .index = DT_XO, },
+		},
+		.num_parents = 1,
+		.ops = &clk_alpha_pll_hwfsm_ops,
+	},
+};
+
+static struct clk_fixed_factor cbf_pll_postdiv = {
+	.mult = 1,
+	.div = 2,
+	.hw.init = &(struct clk_init_data){
+		.name = "cbf_pll_postdiv",
+		.parent_hws = (const struct clk_hw*[]){
+			&cbf_pll.clkr.hw
+		},
+		.num_parents = 1,
+		.ops = &clk_fixed_factor_ops,
+		.flags = CLK_SET_RATE_PARENT,
+	},
+};
+
+static const struct clk_parent_data cbf_mux_parent_data[] = {
+	{ .index = DT_XO },
+	{ .hw = &cbf_pll.clkr.hw },
+	{ .hw = &cbf_pll_postdiv.hw },
+	{ .index = DT_APCS_AUX },
+};
+
+struct clk_cbf_8996_mux {
+	u32 reg;
+	struct notifier_block nb;
+	struct clk_regmap clkr;
+};
+
+static struct clk_cbf_8996_mux *to_clk_cbf_8996_mux(struct clk_regmap *clkr)
+{
+	return container_of(clkr, struct clk_cbf_8996_mux, clkr);
+}
+
+static int cbf_clk_notifier_cb(struct notifier_block *nb, unsigned long event,
+			       void *data);
+
+static u8 clk_cbf_8996_mux_get_parent(struct clk_hw *hw)
+{
+	struct clk_regmap *clkr = to_clk_regmap(hw);
+	struct clk_cbf_8996_mux *mux = to_clk_cbf_8996_mux(clkr);
+	u32 val;
+
+	regmap_read(clkr->regmap, mux->reg, &val);
+
+	return FIELD_GET(CBF_MUX_PARENT_MASK, val);
+}
+
+static int clk_cbf_8996_mux_set_parent(struct clk_hw *hw, u8 index)
+{
+	struct clk_regmap *clkr = to_clk_regmap(hw);
+	struct clk_cbf_8996_mux *mux = to_clk_cbf_8996_mux(clkr);
+	u32 val;
+
+	val = FIELD_PREP(CBF_MUX_PARENT_MASK, index);
+
+	return regmap_update_bits(clkr->regmap, mux->reg, CBF_MUX_PARENT_MASK, val);
+}
+
+static int clk_cbf_8996_mux_determine_rate(struct clk_hw *hw,
+					   struct clk_rate_request *req)
+{
+	struct clk_hw *parent;
+
+	if (req->rate < (DIV_THRESHOLD / 2))
+		return -EINVAL;
+
+	if (req->rate < DIV_THRESHOLD)
+		parent = clk_hw_get_parent_by_index(hw, CBF_DIV_INDEX);
+	else
+		parent = clk_hw_get_parent_by_index(hw, CBF_PLL_INDEX);
+
+	if (!parent)
+		return -EINVAL;
+
+	req->best_parent_rate = clk_hw_round_rate(parent, req->rate);
+	req->best_parent_hw = parent;
+
+	return 0;
+}
+
+static const struct clk_ops clk_cbf_8996_mux_ops = {
+	.set_parent = clk_cbf_8996_mux_set_parent,
+	.get_parent = clk_cbf_8996_mux_get_parent,
+	.determine_rate = clk_cbf_8996_mux_determine_rate,
+};
+
+static struct clk_cbf_8996_mux cbf_mux = {
+	.reg = CBF_MUX_OFFSET,
+	.nb.notifier_call = cbf_clk_notifier_cb,
+	.clkr.hw.init = &(struct clk_init_data) {
+		.name = "cbf_mux",
+		.parent_data = cbf_mux_parent_data,
+		.num_parents = ARRAY_SIZE(cbf_mux_parent_data),
+		.ops = &clk_cbf_8996_mux_ops,
+		/* CPU clock is critical and should never be gated */
+		.flags = CLK_SET_RATE_PARENT | CLK_IS_CRITICAL,
+	},
+};
+
+static int cbf_clk_notifier_cb(struct notifier_block *nb, unsigned long event,
+			       void *data)
+{
+	struct clk_notifier_data *cnd = data;
+
+	switch (event) {
+	case PRE_RATE_CHANGE:
+		/*
+		 * Avoid overvolting. clk_core_set_rate_nolock() walks from top
+		 * to bottom, so it will change the rate of the PLL before
+		 * chaging the parent of PMUX. This can result in pmux getting
+		 * clocked twice the expected rate.
+		 *
+		 * Manually switch to PLL/2 here.
+		 */
+		if (cnd->old_rate > DIV_THRESHOLD &&
+		    cnd->new_rate < DIV_THRESHOLD)
+			clk_cbf_8996_mux_set_parent(&cbf_mux.clkr.hw, CBF_DIV_INDEX);
+		break;
+	case ABORT_RATE_CHANGE:
+		/* Revert manual change */
+		if (cnd->new_rate < DIV_THRESHOLD &&
+		    cnd->old_rate > DIV_THRESHOLD)
+			clk_cbf_8996_mux_set_parent(&cbf_mux.clkr.hw, CBF_PLL_INDEX);
+		break;
+	default:
+		break;
+	}
+
+	return notifier_from_errno(0);
+};
+
+static struct clk_hw *cbf_msm8996_hw_clks[] = {
+	&cbf_pll_postdiv.hw,
+};
+
+static struct clk_regmap *cbf_msm8996_clks[] = {
+	&cbf_pll.clkr,
+	&cbf_mux.clkr,
+};
+
+static const struct regmap_config cbf_msm8996_regmap_config = {
+	.reg_bits		= 32,
+	.reg_stride		= 4,
+	.val_bits		= 32,
+	.max_register		= 0x10000,
+	.fast_io		= true,
+	.val_format_endian	= REGMAP_ENDIAN_LITTLE,
+};
+
+static int qcom_msm8996_cbf_probe(struct platform_device *pdev)
+{
+	void __iomem *base;
+	struct regmap *regmap;
+	struct device *dev = &pdev->dev;
+	int i, ret;
+
+	base = devm_platform_ioremap_resource(pdev, 0);
+	if (IS_ERR(base))
+		return PTR_ERR(base);
+
+	regmap = devm_regmap_init_mmio(dev, base, &cbf_msm8996_regmap_config);
+	if (IS_ERR(regmap))
+		return PTR_ERR(regmap);
+
+	/* Select GPLL0 for 300MHz for the CBF clock */
+	regmap_write(regmap, CBF_MUX_OFFSET, 0x3);
+
+	/* Ensure write goes through before PLLs are reconfigured */
+	udelay(5);
+
+	/* Set the auto clock sel always-on source to GPLL0/2 (300MHz) */
+	regmap_update_bits(regmap, CBF_MUX_OFFSET,
+			   CBF_MUX_AUTO_CLK_SEL_ALWAYS_ON_MASK,
+			   CBF_MUX_AUTO_CLK_SEL_ALWAYS_ON_GPLL0_SEL);
+
+	clk_alpha_pll_configure(&cbf_pll, regmap, &cbfpll_config);
+
+	/* Wait for PLL(s) to lock */
+	udelay(50);
+
+	/* Enable auto clock selection for CBF */
+	regmap_update_bits(regmap, CBF_MUX_OFFSET,
+			   CBF_MUX_AUTO_CLK_SEL_BIT,
+			   CBF_MUX_AUTO_CLK_SEL_BIT);
+
+	/* Ensure write goes through before muxes are switched */
+	udelay(5);
+
+	/* Switch CBF to use the primary PLL */
+	regmap_update_bits(regmap, CBF_MUX_OFFSET, CBF_MUX_PARENT_MASK, 0x1);
+
+	for (i = 0; i < ARRAY_SIZE(cbf_msm8996_hw_clks); i++) {
+		ret = devm_clk_hw_register(dev, cbf_msm8996_hw_clks[i]);
+		if (ret)
+			return ret;
+	}
+
+	for (i = 0; i < ARRAY_SIZE(cbf_msm8996_clks); i++) {
+		ret = devm_clk_register_regmap(dev, cbf_msm8996_clks[i]);
+		if (ret)
+			return ret;
+	}
+
+	ret = devm_clk_notifier_register(dev, cbf_mux.clkr.hw.clk, &cbf_mux.nb);
+	if (ret)
+		return ret;
+
+	return devm_of_clk_add_hw_provider(dev, of_clk_hw_simple_get, &cbf_mux.clkr.hw);
+}
+
+static const struct of_device_id qcom_msm8996_cbf_match_table[] = {
+	{ .compatible = "qcom,msm8996-cbf" },
+	{ /* sentinel */ },
+};
+MODULE_DEVICE_TABLE(of, qcom_msm8996_cbf_match_table);
+
+static struct platform_driver qcom_msm8996_cbf_driver = {
+	.probe = qcom_msm8996_cbf_probe,
+	.driver = {
+		.name = "qcom-msm8996-cbf",
+		.of_match_table = qcom_msm8996_cbf_match_table,
+	},
+};
+
+/* Register early enough to fix the clock to be used for other cores */
+static int __init qcom_msm8996_cbf_init(void)
+{
+	return platform_driver_register(&qcom_msm8996_cbf_driver);
+}
+postcore_initcall(qcom_msm8996_cbf_init);
+
+static void __exit qcom_msm8996_cbf_exit(void)
+{
+	platform_driver_unregister(&qcom_msm8996_cbf_driver);
+}
+module_exit(qcom_msm8996_cbf_exit);
+
+MODULE_DESCRIPTION("QCOM MSM8996 CPU Bus Fabric Clock Driver");
+MODULE_LICENSE("GPL");