clk: Add Baikal-T1 CCU PLLs driver

Baikal-T1 is supposed to be supplied with a high-frequency external
oscillator. But in order to create signals suitable for each IP-block
embedded into the SoC the oscillator output is primarily connected to
a set of CCU PLLs. There are five of them to create clocks for the MIPS
P5600 cores, an embedded DDR controller, SATA, Ethernet and PCIe domains.
The last three domains though named by the biggest system interfaces in
fact include nearly all of the rest SoC peripherals. Each of the PLLs is
based on True Circuits TSMC CLN28HPM IP-core with an interface wrapper
(so called safe PLL' clocks switcher) to simplify the PLL configuration
procedure.

This driver creates the of-based hardware clocks to use them then in
the corresponding subsystems. In order to simplify the driver code we
split the functionality up into the PLLs clocks operations and hardware
clocks declaration/registration procedures.

Even though the PLLs are based on the same IP-core, they may have some
differences. In particular, some CCU PLLs support the output clock change
without gating them (like CPU or PCIe PLLs), while the others don't, some
CCU PLLs are critical and aren't supposed to be gated. In order to cover
all of these cases the hardware clocks driver is designed with an
info-descriptor pattern. So there are special static descriptors declared
for each PLL, which is then used to create a hardware clock with proper
operations. Additionally debugfs-files are provided for each PLL' field
to make sure the implemented rate-PLLs-dividers calculation algorithm is
correct.
Signed-off-by: Serge Semin <Sergey.Semin@baikalelectronics.ru>
Cc: Alexey Malahov <Alexey.Malahov@baikalelectronics.ru>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Rob Herring <robh+dt@kernel.org>
Cc: linux-mips@vger.kernel.org
Cc: devicetree@vger.kernel.org
Link: https://lore.kernel.org/r/20200526222056.18072-4-Sergey.Semin@baikalelectronics.ru
[sboyd@kernel.org: Silence sparse warning about initializing structs
with NULL vs. integer]
Signed-off-by: Stephen Boyd <sboyd@kernel.org>

drivers/clk/Kconfig

@@ -341,6 +341,7 @@ config COMMON_CLK_FIXED_MMIO
 
 source "drivers/clk/actions/Kconfig"
 source "drivers/clk/analogbits/Kconfig"
+source "drivers/clk/baikal-t1/Kconfig"
 source "drivers/clk/bcm/Kconfig"
 source "drivers/clk/hisilicon/Kconfig"
 source "drivers/clk/imgtec/Kconfig"

drivers/clk/Makefile

@@ -75,6 +75,7 @@ obj-y					+= analogbits/
 obj-$(CONFIG_COMMON_CLK_AT91)		+= at91/
 obj-$(CONFIG_ARCH_ARTPEC)		+= axis/
 obj-$(CONFIG_ARC_PLAT_AXS10X)		+= axs10x/
+obj-$(CONFIG_CLK_BAIKAL_T1)		+= baikal-t1/
 obj-y					+= bcm/
 obj-$(CONFIG_ARCH_BERLIN)		+= berlin/
 obj-$(CONFIG_ARCH_DAVINCI)		+= davinci/

drivers/clk/baikal-t1/Kconfig

+# SPDX-License-Identifier: GPL-2.0-only
+config CLK_BAIKAL_T1
+	bool "Baikal-T1 Clocks Control Unit interface"
+	depends on (MIPS_BAIKAL_T1 && OF) || COMPILE_TEST
+	default MIPS_BAIKAL_T1
+	help
+	  Clocks Control Unit is the core of Baikal-T1 SoC System Controller
+	  responsible for the chip subsystems clocking and resetting. It
+	  consists of multiple global clock domains, which can be reset by
+	  means of the CCU control registers. These domains and devices placed
+	  in them are fed with clocks generated by a hierarchy of PLLs,
+	  configurable and fixed clock dividers. Enable this option to be able
+	  to select Baikal-T1 CCU PLLs and Dividers drivers.
+
+if CLK_BAIKAL_T1
+
+config CLK_BT1_CCU_PLL
+	bool "Baikal-T1 CCU PLLs support"
+	select MFD_SYSCON
+	default MIPS_BAIKAL_T1
+	help
+	  Enable this to support the PLLs embedded into the Baikal-T1 SoC
+	  System Controller. These are five PLLs placed at the root of the
+	  clocks hierarchy, right after an external reference oscillator
+	  (normally of 25MHz). They are used to generate high frequency
+	  signals, which are either directly wired to the consumers (like
+	  CPUs, DDR, etc.) or passed over the clock dividers to be only
+	  then used as an individual reference clock of a target device.
+
+endif

drivers/clk/baikal-t1/Makefile

+# SPDX-License-Identifier: GPL-2.0-only
+obj-$(CONFIG_CLK_BT1_CCU_PLL) += ccu-pll.o clk-ccu-pll.o

drivers/clk/baikal-t1/ccu-pll.h

+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Copyright (C) 2020 BAIKAL ELECTRONICS, JSC
+ *
+ * Baikal-T1 CCU PLL interface driver
+ */
+#ifndef __CLK_BT1_CCU_PLL_H__
+#define __CLK_BT1_CCU_PLL_H__
+
+#include <linux/clk-provider.h>
+#include <linux/spinlock.h>
+#include <linux/regmap.h>
+#include <linux/bits.h>
+#include <linux/of.h>
+
+/*
+ * struct ccu_pll_init_data - CCU PLL initialization data
+ * @id: Clock private identifier.
+ * @name: Clocks name.
+ * @parent_name: Clocks parent name in a fw node.
+ * @base: PLL registers base address with respect to the sys_regs base.
+ * @sys_regs: Baikal-T1 System Controller registers map.
+ * @np: Pointer to the node describing the CCU PLLs.
+ * @flags: PLL clock flags.
+ */
+struct ccu_pll_init_data {
+	unsigned int id;
+	const char *name;
+	const char *parent_name;
+	unsigned int base;
+	struct regmap *sys_regs;
+	struct device_node *np;
+	unsigned long flags;
+};
+
+/*
+ * struct ccu_pll - CCU PLL descriptor
+ * @hw: clk_hw of the PLL.
+ * @id: Clock private identifier.
+ * @reg_ctl: PLL control register base.
+ * @reg_ctl1: PLL control1 register base.
+ * @sys_regs: Baikal-T1 System Controller registers map.
+ * @lock: PLL state change spin-lock.
+ */
+struct ccu_pll {
+	struct clk_hw hw;
+	unsigned int id;
+	unsigned int reg_ctl;
+	unsigned int reg_ctl1;
+	struct regmap *sys_regs;
+	spinlock_t lock;
+};
+#define to_ccu_pll(_hw) container_of(_hw, struct ccu_pll, hw)
+
+static inline struct clk_hw *ccu_pll_get_clk_hw(struct ccu_pll *pll)
+{
+	return pll ? &pll->hw : NULL;
+}
+
+struct ccu_pll *ccu_pll_hw_register(const struct ccu_pll_init_data *init);
+
+void ccu_pll_hw_unregister(struct ccu_pll *pll);
+
+#endif /* __CLK_BT1_CCU_PLL_H__ */

drivers/clk/baikal-t1/clk-ccu-pll.c

+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) 2020 BAIKAL ELECTRONICS, JSC
+ *
+ * Authors:
+ *   Serge Semin <Sergey.Semin@baikalelectronics.ru>
+ *   Dmitry Dunaev <dmitry.dunaev@baikalelectronics.ru>
+ *
+ * Baikal-T1 CCU PLL clocks driver
+ */
+
+#define pr_fmt(fmt) "bt1-ccu-pll: " fmt
+
+#include <linux/kernel.h>
+#include <linux/printk.h>
+#include <linux/slab.h>
+#include <linux/clk-provider.h>
+#include <linux/mfd/syscon.h>
+#include <linux/of.h>
+#include <linux/of_address.h>
+#include <linux/ioport.h>
+#include <linux/regmap.h>
+
+#include <dt-bindings/clock/bt1-ccu.h>
+
+#include "ccu-pll.h"
+
+#define CCU_CPU_PLL_BASE		0x000
+#define CCU_SATA_PLL_BASE		0x008
+#define CCU_DDR_PLL_BASE		0x010
+#define CCU_PCIE_PLL_BASE		0x018
+#define CCU_ETH_PLL_BASE		0x020
+
+#define CCU_PLL_INFO(_id, _name, _pname, _base, _flags)	\
+	{						\
+		.id = _id,				\
+		.name = _name,				\
+		.parent_name = _pname,			\
+		.base = _base,				\
+		.flags = _flags				\
+	}
+
+#define CCU_PLL_NUM			ARRAY_SIZE(pll_info)
+
+struct ccu_pll_info {
+	unsigned int id;
+	const char *name;
+	const char *parent_name;
+	unsigned int base;
+	unsigned long flags;
+};
+
+/*
+ * Mark as critical all PLLs except Ethernet one. CPU and DDR PLLs are sources
+ * of CPU cores and DDR controller reference clocks, due to which they
+ * obviously shouldn't be ever gated. SATA and PCIe PLLs are the parents of
+ * APB-bus and DDR controller AXI-bus clocks. If they are gated the system will
+ * be unusable.
+ */
+static const struct ccu_pll_info pll_info[] = {
+	CCU_PLL_INFO(CCU_CPU_PLL, "cpu_pll", "ref_clk", CCU_CPU_PLL_BASE,
+		     CLK_IS_CRITICAL),
+	CCU_PLL_INFO(CCU_SATA_PLL, "sata_pll", "ref_clk", CCU_SATA_PLL_BASE,
+		     CLK_IS_CRITICAL | CLK_SET_RATE_GATE),
+	CCU_PLL_INFO(CCU_DDR_PLL, "ddr_pll", "ref_clk", CCU_DDR_PLL_BASE,
+		     CLK_IS_CRITICAL | CLK_SET_RATE_GATE),
+	CCU_PLL_INFO(CCU_PCIE_PLL, "pcie_pll", "ref_clk", CCU_PCIE_PLL_BASE,
+		     CLK_IS_CRITICAL),
+	CCU_PLL_INFO(CCU_ETH_PLL, "eth_pll", "ref_clk", CCU_ETH_PLL_BASE,
+		     CLK_SET_RATE_GATE)
+};
+
+struct ccu_pll_data {
+	struct device_node *np;
+	struct regmap *sys_regs;
+	struct ccu_pll *plls[CCU_PLL_NUM];
+};
+
+static struct ccu_pll *ccu_pll_find_desc(struct ccu_pll_data *data,
+					 unsigned int clk_id)
+{
+	struct ccu_pll *pll;
+	int idx;
+
+	for (idx = 0; idx < CCU_PLL_NUM; ++idx) {
+		pll = data->plls[idx];
+		if (pll && pll->id == clk_id)
+			return pll;
+	}
+
+	return ERR_PTR(-EINVAL);
+}
+
+static struct ccu_pll_data *ccu_pll_create_data(struct device_node *np)
+{
+	struct ccu_pll_data *data;
+
+	data = kzalloc(sizeof(*data), GFP_KERNEL);
+	if (!data)
+		return ERR_PTR(-ENOMEM);
+
+	data->np = np;
+
+	return data;
+}
+
+static void ccu_pll_free_data(struct ccu_pll_data *data)
+{
+	kfree(data);
+}
+
+static int ccu_pll_find_sys_regs(struct ccu_pll_data *data)
+{
+	data->sys_regs = syscon_node_to_regmap(data->np->parent);
+	if (IS_ERR(data->sys_regs)) {
+		pr_err("Failed to find syscon regs for '%s'\n",
+			of_node_full_name(data->np));
+		return PTR_ERR(data->sys_regs);
+	}
+
+	return 0;
+}
+
+static struct clk_hw *ccu_pll_of_clk_hw_get(struct of_phandle_args *clkspec,
+					    void *priv)
+{
+	struct ccu_pll_data *data = priv;
+	struct ccu_pll *pll;
+	unsigned int clk_id;
+
+	clk_id = clkspec->args[0];
+	pll = ccu_pll_find_desc(data, clk_id);
+	if (IS_ERR(pll)) {
+		pr_info("Invalid PLL clock ID %d specified\n", clk_id);
+		return ERR_CAST(pll);
+	}
+
+	return ccu_pll_get_clk_hw(pll);
+}
+
+static int ccu_pll_clk_register(struct ccu_pll_data *data)
+{
+	int idx, ret;
+
+	for (idx = 0; idx < CCU_PLL_NUM; ++idx) {
+		const struct ccu_pll_info *info = &pll_info[idx];
+		struct ccu_pll_init_data init = {0};
+
+		init.id = info->id;
+		init.name = info->name;
+		init.parent_name = info->parent_name;
+		init.base = info->base;
+		init.sys_regs = data->sys_regs;
+		init.np = data->np;
+		init.flags = info->flags;
+
+		data->plls[idx] = ccu_pll_hw_register(&init);
+		if (IS_ERR(data->plls[idx])) {
+			ret = PTR_ERR(data->plls[idx]);
+			pr_err("Couldn't register PLL hw '%s'\n",
+				init.name);
+			goto err_hw_unregister;
+		}
+	}
+
+	ret = of_clk_add_hw_provider(data->np, ccu_pll_of_clk_hw_get, data);
+	if (ret) {
+		pr_err("Couldn't register PLL provider of '%s'\n",
+			of_node_full_name(data->np));
+		goto err_hw_unregister;
+	}
+
+	return 0;
+
+err_hw_unregister:
+	for (--idx; idx >= 0; --idx)
+		ccu_pll_hw_unregister(data->plls[idx]);
+
+	return ret;
+}
+
+static __init void ccu_pll_init(struct device_node *np)
+{
+	struct ccu_pll_data *data;
+	int ret;
+
+	data = ccu_pll_create_data(np);
+	if (IS_ERR(data))
+		return;
+
+	ret = ccu_pll_find_sys_regs(data);
+	if (ret)
+		goto err_free_data;
+
+	ret = ccu_pll_clk_register(data);
+	if (ret)
+		goto err_free_data;
+
+	return;
+
+err_free_data:
+	ccu_pll_free_data(data);
+}
+CLK_OF_DECLARE(ccu_pll, "baikal,bt1-ccu-pll", ccu_pll_init);