i3c: ast2600: Add AST2600 platform-specific driver

Now that we have platform-specific infrastructure for the dw i3c driver,
add platform support for the ASPEED AST2600 SoC.

The AST2600 has a small set of "i3c global" registers, providing
platform-level i3c configuration outside of the i3c core.

For the ast2600, we need a couple of extra setup operations:

- on probe: find the i3c global register set and parse the SDA pullup
resistor values

- on init: set the pullups accordingly, and set the i3c instance IDs

Signed-off-by: Jeremy Kerr <[e-mail]>
Reviewed-by: Joel Stanley <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Alexandre Belloni <[e-mail]>

MAINTAINERS

···
 F:	Documentation/devicetree/bindings/i3c/snps,dw-i3c-master.yaml
 F:	drivers/i3c/master/dw*
 
+I3C DRIVER FOR ASPEED AST2600
+M:	Jeremy Kerr <[e-mail]>
+S:	Maintained
+F:	Documentation/devicetree/bindings/i3c/aspeed,ast2600-i3c.yaml
+F:	drivers/i3c/master/ast2600-i3c-master.c
+
 I3C SUBSYSTEM
 M:	Alexandre Belloni <[e-mail]>
 L:	[e-mail] (moderated for non-subscribers)

drivers/i3c/master/Kconfig

···
 	  This driver can also be built as a module.  If so, the module
 	  will be called dw-i3c-master.
 
+config AST2600_I3C_MASTER
+	tristate "ASPEED AST2600 I3C master driver"
+	depends on DW_I3C_MASTER
+	depends on ARCH_ASPEED || COMPILE_TEST
+	select MFD_SYSCON
+	help
+	  Support for ASPEED AST2600 I3C Controller.
+
+	  This hardware is an instance of the DW I3C controller; this
+	  driver adds platform- specific support for AST2600 hardware.
+
+	  This driver can also be built as a module.  If so, the module
+	  will be called ast2600-i3c-master.
+
 config SVC_I3C_MASTER
 	tristate "Silvaco I3C Dual-Role Master driver"
 	depends on I3C

drivers/i3c/master/Makefile

···
 # SPDX-License-Identifier: GPL-2.0-only
 obj-$(CONFIG_CDNS_I3C_MASTER)		+= i3c-master-cdns.o
 obj-$(CONFIG_DW_I3C_MASTER)		+= dw-i3c-master.o
+obj-$(CONFIG_AST2600_I3C_MASTER)	+= ast2600-i3c-master.o
 obj-$(CONFIG_SVC_I3C_MASTER)		+= svc-i3c-master.o
 obj-$(CONFIG_MIPI_I3C_HCI)		+= mipi-i3c-hci/

drivers/i3c/master/ast2600-i3c-master.c

···
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (c) 2023 Code Construct
+ *
+ * Author: Jeremy Kerr <[e-mail]>
+ */
+
+#include <linux/mfd/syscon.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/of_device.h>
+#include <linux/platform_device.h>
+#include <linux/regmap.h>
+
+#include "dw-i3c-master.h"
+
+/* AST2600-specific global register set */
+#define AST2600_I3CG_REG0(idx)	(((idx) * 4 * 4) + 0x10)
+#define AST2600_I3CG_REG1(idx)	(((idx) * 4 * 4) + 0x14)
+
+#define AST2600_I3CG_REG0_SDA_PULLUP_EN_MASK	GENMASK(29, 28)
+#define AST2600_I3CG_REG0_SDA_PULLUP_EN_2K	(0x0 << 28)
+#define AST2600_I3CG_REG0_SDA_PULLUP_EN_750	(0x2 << 28)
+
+#define AST2600_I3CG_REG1_I2C_MODE		BIT(0)
+#define AST2600_I3CG_REG1_TEST_MODE		BIT(1)
+#define AST2600_I3CG_REG1_ACT_MODE_MASK		GENMASK(3, 2)
+#define AST2600_I3CG_REG1_ACT_MODE(x)		(((x) << 2) & AST2600_I3CG_REG1_ACT_MODE_MASK)
+#define AST2600_I3CG_REG1_PENDING_INT_MASK	GENMASK(7, 4)
+#define AST2600_I3CG_REG1_PENDING_INT(x)	(((x) << 4) & AST2600_I3CG_REG1_PENDING_INT_MASK)
+#define AST2600_I3CG_REG1_SA_MASK		GENMASK(14, 8)
+#define AST2600_I3CG_REG1_SA(x)			(((x) << 8) & AST2600_I3CG_REG1_SA_MASK)
+#define AST2600_I3CG_REG1_SA_EN			BIT(15)
+#define AST2600_I3CG_REG1_INST_ID_MASK		GENMASK(19, 16)
+#define AST2600_I3CG_REG1_INST_ID(x)		(((x) << 16) & AST2600_I3CG_REG1_INST_ID_MASK)
+
+#define AST2600_DEFAULT_SDA_PULLUP_OHMS		2000
+
+struct ast2600_i3c {
+	struct dw_i3c_master dw;
+	struct regmap *global_regs;
+	unsigned int global_idx;
+	unsigned int sda_pullup;
+};
+
+static struct ast2600_i3c *to_ast2600_i3c(struct dw_i3c_master *dw)
+{
+	return container_of(dw, struct ast2600_i3c, dw);
+}
+
+static int ast2600_i3c_pullup_to_reg(unsigned int ohms, u32 *regp)
+{
+	u32 reg;
+
+	switch (ohms) {
+	case 2000:
+		reg = AST2600_I3CG_REG0_SDA_PULLUP_EN_2K;
+		break;
+	case 750:
+		reg = AST2600_I3CG_REG0_SDA_PULLUP_EN_750;
+		break;
+	case 545:
+		reg = AST2600_I3CG_REG0_SDA_PULLUP_EN_2K |
+			AST2600_I3CG_REG0_SDA_PULLUP_EN_750;
+		break;
+	default:
+		return -EINVAL;
+	}
+
+	if (regp)
+		*regp = reg;
+
+	return 0;
+}
+
+static int ast2600_i3c_init(struct dw_i3c_master *dw)
+{
+	struct ast2600_i3c *i3c = to_ast2600_i3c(dw);
+	u32 reg = 0;
+	int rc;
+
+	/* reg0: set SDA pullup values */
+	rc = ast2600_i3c_pullup_to_reg(i3c->sda_pullup, &reg);
+	if (rc)
+		return rc;
+
+	rc = regmap_write(i3c->global_regs,
+			  AST2600_I3CG_REG0(i3c->global_idx), reg);
+	if (rc)
+		return rc;
+
+	/* reg1: set up the instance id, but leave everything else disabled,
+	 * as it's all for client mode
+	 */
+	reg = AST2600_I3CG_REG1_INST_ID(i3c->global_idx);
+	rc = regmap_write(i3c->global_regs,
+			  AST2600_I3CG_REG1(i3c->global_idx), reg);
+
+	return rc;
+}
+
+const struct dw_i3c_platform_ops ast2600_i3c_ops = {
+	.init = ast2600_i3c_init,
+};
+
+static int ast2600_i3c_probe(struct platform_device *pdev)
+{
+	struct device_node *np = pdev->dev.of_node;
+	struct of_phandle_args gspec;
+	struct ast2600_i3c *i3c;
+	int rc;
+
+	i3c = devm_kzalloc(&pdev->dev, sizeof(*i3c), GFP_KERNEL);
+	if (!i3c)
+		return -ENOMEM;
+
+	rc = of_parse_phandle_with_fixed_args(np, "aspeed,global-regs", 1, 0,
+					      &gspec);
+	if (rc)
+		return -ENODEV;
+
+	i3c->global_regs = syscon_node_to_regmap(gspec.np);
+	of_node_put(gspec.np);
+
+	if (IS_ERR(i3c->global_regs))
+		return PTR_ERR(i3c->global_regs);
+
+	i3c->global_idx = gspec.args[0];
+
+	rc = of_property_read_u32(np, "sda-pullup-ohms", &i3c->sda_pullup);
+	if (rc)
+		i3c->sda_pullup = AST2600_DEFAULT_SDA_PULLUP_OHMS;
+
+	rc = ast2600_i3c_pullup_to_reg(i3c->sda_pullup, NULL);
+	if (rc)
+		dev_err(&pdev->dev, "invalid sda-pullup value %d\n",
+			i3c->sda_pullup);
+
+	i3c->dw.platform_ops = &ast2600_i3c_ops;
+	return dw_i3c_common_probe(&i3c->dw, pdev);
+}
+
+static void ast2600_i3c_remove(struct platform_device *pdev)
+{
+	struct dw_i3c_master *dw_i3c = platform_get_drvdata(pdev);
+
+	dw_i3c_common_remove(dw_i3c);
+}
+
+static const struct of_device_id ast2600_i3c_master_of_match[] = {
+	{ .compatible = "aspeed,ast2600-i3c", },
+	{},
+};
+MODULE_DEVICE_TABLE(of, ast2600_i3c_master_of_match);
+
+static struct platform_driver ast2600_i3c_driver = {
+	.probe = ast2600_i3c_probe,
+	.remove_new = ast2600_i3c_remove,
+	.driver = {
+		.name = "ast2600-i3c-master",
+		.of_match_table = ast2600_i3c_master_of_match,
+	},
+};
+module_platform_driver(ast2600_i3c_driver);
+
+MODULE_AUTHOR("Jeremy Kerr <[e-mail]>");
+MODULE_DESCRIPTION("ASPEED AST2600 I3C driver");
+MODULE_LICENSE("GPL");