clk: ux500: Add driver for the reset portions of PRCC

The Ux500 PRCC (peripheral reset and clock controller) can also
control reset of the IP blocks, not just clocks. As the PRCC is probed
as a clock controller and we have other platforms implementing combined
clock and reset controllers, follow this pattern and implement the PRCC
rest controller as part of the clock driver.

The reset controller needs to be selected from the machine as Ux500 has
traditionally selected its mandatory subsystem prerequisites from there.

Cc: Philipp Zabel <[e-mail]>
Cc: Ulf Hansson <[e-mail]>
Signed-off-by: Linus Walleij <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Acked-by: Ulf Hansson <[e-mail]>
[[e-mail]: Dropped allocation error message]
Signed-off-by: Stephen Boyd <[e-mail]>

arch/arm/mach-ux500/Kconfig

···
 	select REGULATOR_DB8500_PRCMU
 	select REGULATOR_FIXED_VOLTAGE
 	select SOC_BUS
+	select RESET_CONTROLLER
 	help
 	  Support for ST-Ericsson's Ux500 architecture
 

drivers/clk/ux500/Makefile

···
 obj-y += clk-prcmu.o
 obj-y += clk-sysctrl.o
 
+# Reset control
+obj-y += reset-prcc.o
+
 # Clock definitions
 obj-y += u8500_of_clk.o
 

drivers/clk/ux500/prcc.h

···
+/* SPDX-License-Identifier: GPL-2.0-only */
+
+#ifndef __PRCC_H
+#define __PRCC_H
+
+#define PRCC_NUM_PERIPH_CLUSTERS 6
+#define PRCC_PERIPHS_PER_CLUSTER 32
+
+/* CLKRST4 is missing making it hard to index things */
+enum clkrst_index {
+	CLKRST1_INDEX = 0,
+	CLKRST2_INDEX,
+	CLKRST3_INDEX,
+	CLKRST5_INDEX,
+	CLKRST6_INDEX,
+	CLKRST_MAX,
+};
+
+#endif

drivers/clk/ux500/reset-prcc.c

···
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Reset controller portions for the U8500 PRCC
+ * Copyright (C) 2021 Linus Walleij <[e-mail]>
+ */
+#include <linux/of.h>
+#include <linux/of_address.h>
+#include <linux/slab.h>
+#include <linux/io.h>
+#include <linux/err.h>
+#include <linux/types.h>
+#include <linux/reset-controller.h>
+#include <linux/bits.h>
+#include <linux/delay.h>
+
+#include "prcc.h"
+#include "reset-prcc.h"
+
+#define to_u8500_prcc_reset(p) container_of((p), struct u8500_prcc_reset, rcdev)
+
+/* This macro flattens the 2-dimensional PRCC numberspace */
+#define PRCC_RESET_LINE(prcc_num, bit) \
+	(((prcc_num) * PRCC_PERIPHS_PER_CLUSTER) + (bit))
+
+/*
+ * Reset registers in each PRCC - the reset lines are active low
+ * so what you need to do is write a bit for the peripheral you
+ * want to put into reset into the CLEAR register, this will assert
+ * the reset by pulling the line low. SET take the device out of
+ * reset. The status reflects the actual state of the line.
+ */
+#define PRCC_K_SOFTRST_SET		0x018
+#define PRCC_K_SOFTRST_CLEAR		0x01c
+#define PRCC_K_RST_STATUS		0x020
+
+static int prcc_num_to_index(unsigned int num)
+{
+	switch (num) {
+	case 1:
+		return CLKRST1_INDEX;
+	case 2:
+		return CLKRST2_INDEX;
+	case 3:
+		return CLKRST3_INDEX;
+	case 5:
+		return CLKRST5_INDEX;
+	case 6:
+		return CLKRST6_INDEX;
+	}
+	return -EINVAL;
+}
+
+static void __iomem *u8500_prcc_reset_base(struct u8500_prcc_reset *ur,
+					   unsigned long id)
+{
+	unsigned int prcc_num, index;
+
+	prcc_num = id / PRCC_PERIPHS_PER_CLUSTER;
+	index = prcc_num_to_index(prcc_num);
+
+	if (index > ARRAY_SIZE(ur->base))
+		return NULL;
+
+	return ur->base[index];
+}
+
+static int u8500_prcc_reset(struct reset_controller_dev *rcdev,
+			    unsigned long id)
+{
+	struct u8500_prcc_reset *ur = to_u8500_prcc_reset(rcdev);
+	void __iomem *base = u8500_prcc_reset_base(ur, id);
+	unsigned int bit = id % PRCC_PERIPHS_PER_CLUSTER;
+
+	pr_debug("PRCC cycle reset id %lu, bit %u\n", id, bit);
+
+	/*
+	 * Assert reset and then release it. The one microsecond
+	 * delay is found in the vendor reference code.
+	 */
+	writel(BIT(bit), base + PRCC_K_SOFTRST_CLEAR);
+	udelay(1);
+	writel(BIT(bit), base + PRCC_K_SOFTRST_SET);
+	udelay(1);
+
+	return 0;
+}
+
+static int u8500_prcc_reset_assert(struct reset_controller_dev *rcdev,
+				   unsigned long id)
+{
+	struct u8500_prcc_reset *ur = to_u8500_prcc_reset(rcdev);
+	void __iomem *base = u8500_prcc_reset_base(ur, id);
+	unsigned int bit = id % PRCC_PERIPHS_PER_CLUSTER;
+
+	pr_debug("PRCC assert reset id %lu, bit %u\n", id, bit);
+	writel(BIT(bit), base + PRCC_K_SOFTRST_CLEAR);
+
+	return 0;
+}
+
+static int u8500_prcc_reset_deassert(struct reset_controller_dev *rcdev,
+				     unsigned long id)
+{
+	struct u8500_prcc_reset *ur = to_u8500_prcc_reset(rcdev);
+	void __iomem *base = u8500_prcc_reset_base(ur, id);
+	unsigned int bit = id % PRCC_PERIPHS_PER_CLUSTER;
+
+	pr_debug("PRCC deassert reset id %lu, bit %u\n", id, bit);
+	writel(BIT(bit), base + PRCC_K_SOFTRST_SET);
+
+	return 0;
+}
+
+static int u8500_prcc_reset_status(struct reset_controller_dev *rcdev,
+				   unsigned long id)
+{
+	struct u8500_prcc_reset *ur = to_u8500_prcc_reset(rcdev);
+	void __iomem *base = u8500_prcc_reset_base(ur, id);
+	unsigned int bit = id % PRCC_PERIPHS_PER_CLUSTER;
+	u32 val;
+
+	pr_debug("PRCC check status on reset line id %lu, bit %u\n", id, bit);
+	val = readl(base + PRCC_K_RST_STATUS);
+
+	/* Active low so return the inverse value of the bit */
+	return !(val & BIT(bit));
+}
+
+static const struct reset_control_ops u8500_prcc_reset_ops = {
+	.reset = u8500_prcc_reset,
+	.assert = u8500_prcc_reset_assert,
+	.deassert = u8500_prcc_reset_deassert,
+	.status = u8500_prcc_reset_status,
+};
+
+static int u8500_prcc_reset_xlate(struct reset_controller_dev *rcdev,
+				  const struct of_phandle_args *reset_spec)
+{
+	unsigned int prcc_num, bit;
+
+	if (reset_spec->args_count != 2)
+		return -EINVAL;
+
+	prcc_num = reset_spec->args[0];
+	bit = reset_spec->args[1];
+
+	if (prcc_num != 1 && prcc_num != 2 && prcc_num != 3 &&
+	    prcc_num != 5 && prcc_num != 6) {
+		pr_err("%s: invalid PRCC %d\n", __func__, prcc_num);
+		return -EINVAL;
+	}
+
+	pr_debug("located reset line %d at PRCC %d bit %d\n",
+		 PRCC_RESET_LINE(prcc_num, bit), prcc_num, bit);
+
+	return PRCC_RESET_LINE(prcc_num, bit);
+}
+
+void u8500_prcc_reset_init(struct device_node *np, struct u8500_prcc_reset *ur)
+{
+	struct reset_controller_dev *rcdev = &ur->rcdev;
+	int ret;
+	int i;
+
+	for (i = 0; i < CLKRST_MAX; i++) {
+		ur->base[i] = ioremap(ur->phy_base[i], SZ_4K);
+		if (!ur->base[i])
+			pr_err("PRCC failed to remap for reset base %d (%08x)\n",
+			       i, ur->phy_base[i]);
+	}
+
+	rcdev->owner = THIS_MODULE;
+	rcdev->ops = &u8500_prcc_reset_ops;
+	rcdev->of_node = np;
+	rcdev->of_reset_n_cells = 2;
+	rcdev->of_xlate = u8500_prcc_reset_xlate;
+
+	ret = reset_controller_register(rcdev);
+	if (ret)
+		pr_err("PRCC failed to register reset controller\n");
+}

drivers/clk/ux500/reset-prcc.h

···
+/* SPDX-License-Identifier: GPL-2.0-only */
+
+#ifndef __RESET_PRCC_H
+#define __RESET_PRCC_H
+
+#include <linux/reset-controller.h>
+#include <linux/io.h>
+
+/**
+ * struct u8500_prcc_reset - U8500 PRCC reset controller state
+ * @rcdev: reset controller device
+ * @phy_base: the physical base address for each PRCC block
+ * @base: the remapped PRCC bases
+ */
+struct u8500_prcc_reset {
+	struct reset_controller_dev rcdev;
+	u32 phy_base[CLKRST_MAX];
+	void __iomem *base[CLKRST_MAX];
+};
+
+void u8500_prcc_reset_init(struct device_node *np, struct u8500_prcc_reset *ur);
+
+#endif

drivers/clk/ux500/u8500_of_clk.c

···
 #include <linux/of_address.h>
 #include <linux/clk-provider.h>
 #include <linux/mfd/dbx500-prcmu.h>
-#include "clk.h"
 
-#define PRCC_NUM_PERIPH_CLUSTERS 6
-#define PRCC_PERIPHS_PER_CLUSTER 32
+#include "clk.h"
+#include "prcc.h"
+#include "reset-prcc.h"
 
 static struct clk *prcmu_clk[PRCMU_NUM_CLKS];
 static struct clk *prcc_pclk[(PRCC_NUM_PERIPH_CLUSTERS + 1) * PRCC_PERIPHS_PER_CLUSTER];
···
 	return PRCC_SHOW(clk_data, base, bit);
 }
 
-/* CLKRST4 is missing making it hard to index things */
-enum clkrst_index {
-	CLKRST1_INDEX = 0,
-	CLKRST2_INDEX,
-	CLKRST3_INDEX,
-	CLKRST5_INDEX,
-	CLKRST6_INDEX,
-	CLKRST_MAX,
-};
-
 static void u8500_clk_init(struct device_node *np)
 {
 	struct prcmu_fw_version *fw_version;
···
 	const char *sgaclk_parent = NULL;
 	struct clk *clk, *rtc_clk, *twd_clk;
 	u32 bases[CLKRST_MAX];
+	struct u8500_prcc_reset *rstc;
 	int i;
+
+	/*
+	 * We allocate the reset controller here so that we can fill in the
+	 * base addresses properly and pass to the reset controller init
+	 * function later on.
+	 */
+	rstc = kzalloc(sizeof(*rstc), GFP_KERNEL);
+	if (!rstc)
+		return;
 
 	for (i = 0; i < ARRAY_SIZE(bases); i++) {
 		struct resource r;
···
 			pr_err("failed to get CLKRST %d base address\n",
 			       i + 1);
 		bases[i] = r.start;
+		rstc->phy_base[i] = r.start;
 	}
 
 	/* Clock sources */
···
 
 		if (of_node_name_eq(child, "smp-twd-clock"))
 			of_clk_add_provider(child, of_clk_src_simple_get, twd_clk);
+
+		if (of_node_name_eq(child, "prcc-reset-controller"))
+			u8500_prcc_reset_init(child, rstc);
 	}
 }
 CLK_OF_DECLARE(u8500_clks, "stericsson,u8500-clks", u8500_clk_init);