x86: tangier: pinmux: add API to configure protected pins

This API is going to be used to configure some pins that are protected
for simple modification.

It's not a comprehensive pinctrl driver but can be turned into one
when we need this in the future. Now it is planned to be used only
in one place. So that's why I decided not to pollute the codebase with a
full-blown pinctrl-merrifield nobody will use.

This driver reads corresponding fields in DT and configures pins
accordingly.

The "protected" flag is used to distinguish configuration of SCU-owned
pins from the ordinary ones.

The code has been adapted from Linux work done by Andy Shevchenko
in pinctrl-merrfifield.c

Signed-off-by: Georgii Staroselskii <georgii.staroselskii@emlid.com>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
[bmeng: fix build warning]
Signed-off-by: Bin Meng <bmeng.cn@gmail.com>

arch/x86/cpu/tangier/Makefile

@@ -2,5 +2,5 @@
 #
 # Copyright (c) 2017 Intel Corporation
 
-obj-y += car.o tangier.o sdram.o sysreset.o
+obj-y += car.o tangier.o sdram.o sysreset.o pinmux.o
 obj-$(CONFIG_GENERATE_ACPI_TABLE) += acpi.o

arch/x86/cpu/tangier/pinmux.c

@@ -0,0 +1,194 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Copyright (c) 2018 Emlid Limited
+ */
+
+#include <common.h>
+#include <dm.h>
+#include <dm/pinctrl.h>
+#include <dm/read.h>
+#include <regmap.h>
+#include <syscon.h>
+#include <asm/cpu.h>
+#include <asm/scu.h>
+#include <linux/io.h>
+
+#define BUFCFG_OFFSET				0x100
+
+#define MRFLD_FAMILY_LEN			0x400
+
+/* These are taken from Linux kernel */
+#define MRFLD_PINMODE_MASK			0x07
+
+#define pin_to_bufno(f, p)			((p) - (f)->pin_base)
+
+struct mrfld_family {
+	unsigned int family_number;
+	unsigned int pin_base;
+	size_t npins;
+	void __iomem *regs;
+};
+
+#define MRFLD_FAMILY(b, s, e)				\
+	{						\
+		.family_number = (b),			\
+		.pin_base = (s),			\
+		.npins = (e) - (s) + 1,			\
+	}
+
+/* Now we only support I2C family of pins */
+static struct mrfld_family mrfld_families[] = {
+	MRFLD_FAMILY(7, 101, 114),
+};
+
+struct mrfld_pinctrl {
+	const struct mrfld_family *families;
+	size_t nfamilies;
+};
+
+static const struct mrfld_family *
+mrfld_get_family(struct mrfld_pinctrl *mp, unsigned int pin)
+{
+	const struct mrfld_family *family;
+	unsigned int i;
+
+	for (i = 0; i < mp->nfamilies; i++) {
+		family = &mp->families[i];
+		if (pin >= family->pin_base &&
+		    pin < family->pin_base + family->npins)
+			return family;
+	}
+
+	pr_err("failed to find family for pin %u\n", pin);
+	return NULL;
+}
+
+static void __iomem *
+mrfld_get_bufcfg(struct mrfld_pinctrl *pinctrl, unsigned int pin)
+{
+	const struct mrfld_family *family;
+	unsigned int bufno;
+
+	family =  mrfld_get_family(pinctrl, pin);
+	if (!family)
+		return NULL;
+
+	bufno = pin_to_bufno(family, pin);
+
+	return family->regs + BUFCFG_OFFSET + bufno * 4;
+}
+
+static void
+mrfld_setup_families(void *base_addr,
+		     struct mrfld_family *families, unsigned int nfam)
+{
+	for (int i = 0; i < nfam; i++) {
+		struct mrfld_family *family = &families[i];
+
+		family->regs = base_addr +
+			       family->family_number * MRFLD_FAMILY_LEN;
+	}
+}
+
+static int mrfld_pinconfig_protected(unsigned int pin, u32 mask, u32 bits)
+{
+	struct mrfld_pinctrl *pinctrl;
+	struct udevice *dev;
+	void __iomem *bufcfg;
+	u32 v, value;
+	int ret;
+
+	ret = syscon_get_by_driver_data(X86_SYSCON_PINCONF, &dev);
+	if (ret)
+		return ret;
+
+	pinctrl = dev_get_priv(dev);
+
+	bufcfg = mrfld_get_bufcfg(pinctrl, pin);
+	if (!bufcfg)
+		return -EINVAL;
+
+	value = readl(bufcfg);
+
+	v = (value & ~mask) | (bits & mask);
+
+	debug("scu: v: 0x%x p: 0x%x bits: %d, mask: %d bufcfg: 0x%p\n",
+	      v, (u32)bufcfg, bits, mask, bufcfg);
+
+	ret = scu_ipc_raw_command(IPCMSG_INDIRECT_WRITE, 0, &v, 4,
+				  NULL, 0, (u32)bufcfg, 0);
+	if (ret)
+		pr_err("Failed to set mode via SCU for pin %u (%d)\n",
+		       pin, ret);
+
+	return ret;
+}
+
+static int mrfld_pinctrl_cfg_pin(ofnode pin_node)
+{
+	bool is_protected;
+	int pad_offset;
+	int mode;
+	u32 mask;
+	int ret;
+
+	/* For now we only support just protected Family of pins */
+	is_protected = ofnode_read_bool(pin_node, "protected");
+	if (!is_protected)
+		return -ENOTSUPP;
+
+	pad_offset = ofnode_read_s32_default(pin_node, "pad-offset", -1);
+	if (pad_offset == -1)
+		return -EINVAL;
+
+	mode = ofnode_read_s32_default(pin_node, "mode-func", -1);
+	if (mode == -1)
+		return -EINVAL;
+
+	mask = MRFLD_PINMODE_MASK;
+
+	/* We don't support modes not in range 0..7 */
+	if (mode & ~mask)
+		return -ENOTSUPP;
+
+	ret = mrfld_pinconfig_protected(pad_offset, mask, mode);
+
+	return ret;
+}
+
+static int tangier_pinctrl_probe(struct udevice *dev)
+{
+	void *base_addr = syscon_get_first_range(X86_SYSCON_PINCONF);
+	struct mrfld_pinctrl *pinctrl = dev_get_priv(dev);
+	ofnode pin_node;
+	int ret;
+
+	mrfld_setup_families(base_addr, mrfld_families,
+			     ARRAY_SIZE(mrfld_families));
+
+	pinctrl->families = mrfld_families;
+	pinctrl->nfamilies = ARRAY_SIZE(mrfld_families);
+
+	ofnode_for_each_subnode(pin_node, dev_ofnode(dev)) {
+		ret = mrfld_pinctrl_cfg_pin(pin_node);
+		if (ret) {
+			pr_err("%s: invalid configuration for the pin %ld\n",
+			       __func__, pin_node.of_offset);
+		}
+	}
+
+	return 0;
+}
+
+static const struct udevice_id tangier_pinctrl_match[] = {
+	{ .compatible = "intel,pinctrl-tangier", .data = X86_SYSCON_PINCONF },
+	{ /* sentinel */ }
+};
+
+U_BOOT_DRIVER(tangier_pinctrl) = {
+	.name = "tangier_pinctrl",
+	.id = UCLASS_SYSCON,
+	.of_match = tangier_pinctrl_match,
+	.probe = tangier_pinctrl_probe,
+	.priv_auto_alloc_size = sizeof(struct mrfld_pinctrl),
+};