ipmi: add an Aspeed KCS IPMI BMC driver

The KCS (Keyboard Controller Style) interface is used to perform in-band
IPMI communication between a server host and its BMC (BaseBoard Management
Controllers).

This driver exposes the KCS interface on ASpeed SOCs (AST2400 and AST2500)
as a character device. Such SOCs are commonly used as BMCs and this driver
implements the BMC side of the KCS interface.

Signed-off-by: Haiyue Wang <[e-mail]>
Signed-off-by: Corey Minyard <[e-mail]>

Documentation/devicetree/bindings/ipmi/aspeed-kcs-bmc.txt

···
+* Aspeed KCS (Keyboard Controller Style) IPMI interface
+
+The Aspeed SOCs (AST2400 and AST2500) are commonly used as BMCs
+(Baseboard Management Controllers) and the KCS interface can be
+used to perform in-band IPMI communication with their host.
+
+Required properties:
+- compatible : should be one of
+    "aspeed,ast2400-kcs-bmc"
+    "aspeed,ast2500-kcs-bmc"
+- interrupts : interrupt generated by the controller
+- kcs_chan : The LPC channel number in the controller
+- kcs_addr : The host CPU IO map address
+
+
+Example:
+
+    kcs3: kcs3@0 {
+        compatible = "aspeed,ast2500-kcs-bmc";
+        reg = <0x0 0x80>;
+        interrupts = <8>;
+        kcs_chan = <3>;
+        kcs_addr = <0xCA2>;
+        status = "okay";
+    };

drivers/char/ipmi/Kconfig

···
 config IPMI_KCS_BMC
 	tristate
 
+config ASPEED_KCS_IPMI_BMC
+	depends on ARCH_ASPEED || COMPILE_TEST
+	select IPMI_KCS_BMC
+	select REGMAP_MMIO
+	tristate "Aspeed KCS IPMI BMC driver"
+	help
+	  Provides a driver for the KCS (Keyboard Controller Style) IPMI
+	  interface found on Aspeed SOCs (AST2400 and AST2500).
+
+	  The driver implements the BMC side of the KCS contorller, it
+	  provides the access of KCS IO space for BMC side.
+
 config ASPEED_BT_IPMI_BMC
 	depends on ARCH_ASPEED || COMPILE_TEST
        depends on REGMAP && REGMAP_MMIO && MFD_SYSCON

drivers/char/ipmi/Makefile

···
 obj-$(CONFIG_IPMI_POWEROFF) += ipmi_poweroff.o
 obj-$(CONFIG_IPMI_KCS_BMC) += kcs_bmc.o
 obj-$(CONFIG_ASPEED_BT_IPMI_BMC) += bt-bmc.o
+obj-$(CONFIG_ASPEED_KCS_IPMI_BMC) += kcs_bmc_aspeed.o

drivers/char/ipmi/kcs_bmc_aspeed.c

···
+// SPDX-License-Identifier: GPL-2.0
+// Copyright (c) 2015-2018, Intel Corporation.
+
+#define pr_fmt(fmt) "aspeed-kcs-bmc: " fmt
+
+#include <linux/atomic.h>
+#include <linux/errno.h>
+#include <linux/interrupt.h>
+#include <linux/io.h>
+#include <linux/mfd/syscon.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+#include <linux/poll.h>
+#include <linux/regmap.h>
+#include <linux/sched.h>
+#include <linux/slab.h>
+#include <linux/timer.h>
+
+#include "kcs_bmc.h"
+
+
+#define DEVICE_NAME     "ast-kcs-bmc"
+
+#define KCS_CHANNEL_MAX     4
+
+/* mapped to lpc-bmc@0 IO space */
+#define LPC_HICR0            0x000
+#define     LPC_HICR0_LPC3E          BIT(7)
+#define     LPC_HICR0_LPC2E          BIT(6)
+#define     LPC_HICR0_LPC1E          BIT(5)
+#define LPC_HICR2            0x008
+#define     LPC_HICR2_IBFIF3         BIT(3)
+#define     LPC_HICR2_IBFIF2         BIT(2)
+#define     LPC_HICR2_IBFIF1         BIT(1)
+#define LPC_HICR4            0x010
+#define     LPC_HICR4_LADR12AS       BIT(7)
+#define     LPC_HICR4_KCSENBL        BIT(2)
+#define LPC_LADR3H           0x014
+#define LPC_LADR3L           0x018
+#define LPC_LADR12H          0x01C
+#define LPC_LADR12L          0x020
+#define LPC_IDR1             0x024
+#define LPC_IDR2             0x028
+#define LPC_IDR3             0x02C
+#define LPC_ODR1             0x030
+#define LPC_ODR2             0x034
+#define LPC_ODR3             0x038
+#define LPC_STR1             0x03C
+#define LPC_STR2             0x040
+#define LPC_STR3             0x044
+
+/* mapped to lpc-host@80 IO space */
+#define LPC_HICRB            0x080
+#define     LPC_HICRB_IBFIF4         BIT(1)
+#define     LPC_HICRB_LPC4E          BIT(0)
+#define LPC_LADR4            0x090
+#define LPC_IDR4             0x094
+#define LPC_ODR4             0x098
+#define LPC_STR4             0x09C
+
+struct aspeed_kcs_bmc {
+	struct regmap *map;
+};
+
+
+static u8 aspeed_kcs_inb(struct kcs_bmc *kcs_bmc, u32 reg)
+{
+	struct aspeed_kcs_bmc *priv = kcs_bmc_priv(kcs_bmc);
+	u32 val = 0;
+	int rc;
+
+	rc = regmap_read(priv->map, reg, &val);
+	WARN(rc != 0, "regmap_read() failed: %d\n", rc);
+
+	return rc == 0 ? (u8) val : 0;
+}
+
+static void aspeed_kcs_outb(struct kcs_bmc *kcs_bmc, u32 reg, u8 data)
+{
+	struct aspeed_kcs_bmc *priv = kcs_bmc_priv(kcs_bmc);
+	int rc;
+
+	rc = regmap_write(priv->map, reg, data);
+	WARN(rc != 0, "regmap_write() failed: %d\n", rc);
+}
+
+
+/*
+ * AST_usrGuide_KCS.pdf
+ * 2. Background:
+ *   we note D for Data, and C for Cmd/Status, default rules are
+ *     A. KCS1 / KCS2 ( D / C:X / X+4 )
+ *        D / C : CA0h / CA4h
+ *        D / C : CA8h / CACh
+ *     B. KCS3 ( D / C:XX2h / XX3h )
+ *        D / C : CA2h / CA3h
+ *        D / C : CB2h / CB3h
+ *     C. KCS4
+ *        D / C : CA4h / CA5h
+ */
+static void aspeed_kcs_set_address(struct kcs_bmc *kcs_bmc, u16 addr)
+{
+	struct aspeed_kcs_bmc *priv = kcs_bmc_priv(kcs_bmc);
+
+	switch (kcs_bmc->channel) {
+	case 1:
+		regmap_update_bits(priv->map, LPC_HICR4,
+				LPC_HICR4_LADR12AS, 0);
+		regmap_write(priv->map, LPC_LADR12H, addr >> 8);
+		regmap_write(priv->map, LPC_LADR12L, addr & 0xFF);
+		break;
+
+	case 2:
+		regmap_update_bits(priv->map, LPC_HICR4,
+				LPC_HICR4_LADR12AS, LPC_HICR4_LADR12AS);
+		regmap_write(priv->map, LPC_LADR12H, addr >> 8);
+		regmap_write(priv->map, LPC_LADR12L, addr & 0xFF);
+		break;
+
+	case 3:
+		regmap_write(priv->map, LPC_LADR3H, addr >> 8);
+		regmap_write(priv->map, LPC_LADR3L, addr & 0xFF);
+		break;
+
+	case 4:
+		regmap_write(priv->map, LPC_LADR4, ((addr + 1) << 16) |
+			addr);
+		break;
+
+	default:
+		break;
+	}
+}
+
+static void aspeed_kcs_enable_channel(struct kcs_bmc *kcs_bmc, bool enable)
+{
+	struct aspeed_kcs_bmc *priv = kcs_bmc_priv(kcs_bmc);
+
+	switch (kcs_bmc->channel) {
+	case 1:
+		if (enable) {
+			regmap_update_bits(priv->map, LPC_HICR2,
+					LPC_HICR2_IBFIF1, LPC_HICR2_IBFIF1);
+			regmap_update_bits(priv->map, LPC_HICR0,
+					LPC_HICR0_LPC1E, LPC_HICR0_LPC1E);
+		} else {
+			regmap_update_bits(priv->map, LPC_HICR0,
+					LPC_HICR0_LPC1E, 0);
+			regmap_update_bits(priv->map, LPC_HICR2,
+					LPC_HICR2_IBFIF1, 0);
+		}
+		break;
+
+	case 2:
+		if (enable) {
+			regmap_update_bits(priv->map, LPC_HICR2,
+					LPC_HICR2_IBFIF2, LPC_HICR2_IBFIF2);
+			regmap_update_bits(priv->map, LPC_HICR0,
+					LPC_HICR0_LPC2E, LPC_HICR0_LPC2E);
+		} else {
+			regmap_update_bits(priv->map, LPC_HICR0,
+					LPC_HICR0_LPC2E, 0);
+			regmap_update_bits(priv->map, LPC_HICR2,
+					LPC_HICR2_IBFIF2, 0);
+		}
+		break;
+
+	case 3:
+		if (enable) {
+			regmap_update_bits(priv->map, LPC_HICR2,
+					LPC_HICR2_IBFIF3, LPC_HICR2_IBFIF3);
+			regmap_update_bits(priv->map, LPC_HICR0,
+					LPC_HICR0_LPC3E, LPC_HICR0_LPC3E);
+			regmap_update_bits(priv->map, LPC_HICR4,
+					LPC_HICR4_KCSENBL, LPC_HICR4_KCSENBL);
+		} else {
+			regmap_update_bits(priv->map, LPC_HICR0,
+					LPC_HICR0_LPC3E, 0);
+			regmap_update_bits(priv->map, LPC_HICR4,
+					LPC_HICR4_KCSENBL, 0);
+			regmap_update_bits(priv->map, LPC_HICR2,
+					LPC_HICR2_IBFIF3, 0);
+		}
+		break;
+
+	case 4:
+		if (enable)
+			regmap_update_bits(priv->map, LPC_HICRB,
+					LPC_HICRB_IBFIF4 | LPC_HICRB_LPC4E,
+					LPC_HICRB_IBFIF4 | LPC_HICRB_LPC4E);
+		else
+			regmap_update_bits(priv->map, LPC_HICRB,
+					LPC_HICRB_IBFIF4 | LPC_HICRB_LPC4E,
+					0);
+		break;
+
+	default:
+		break;
+	}
+}
+
+static irqreturn_t aspeed_kcs_irq(int irq, void *arg)
+{
+	struct kcs_bmc *kcs_bmc = arg;
+
+	if (!kcs_bmc_handle_event(kcs_bmc))
+		return IRQ_HANDLED;
+
+	return IRQ_NONE;
+}
+
+static int aspeed_kcs_config_irq(struct kcs_bmc *kcs_bmc,
+			struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	int irq;
+
+	irq = platform_get_irq(pdev, 0);
+	if (irq < 0)
+		return irq;
+
+	return devm_request_irq(dev, irq, aspeed_kcs_irq, IRQF_SHARED,
+				dev_name(dev), kcs_bmc);
+}
+
+static const struct kcs_ioreg ast_kcs_bmc_ioregs[KCS_CHANNEL_MAX] = {
+	{ .idr = LPC_IDR1, .odr = LPC_ODR1, .str = LPC_STR1 },
+	{ .idr = LPC_IDR2, .odr = LPC_ODR2, .str = LPC_STR2 },
+	{ .idr = LPC_IDR3, .odr = LPC_ODR3, .str = LPC_STR3 },
+	{ .idr = LPC_IDR4, .odr = LPC_ODR4, .str = LPC_STR4 },
+};
+
+static int aspeed_kcs_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct aspeed_kcs_bmc *priv;
+	struct kcs_bmc *kcs_bmc;
+	u32 chan, addr;
+	int rc;
+
+	rc = of_property_read_u32(dev->of_node, "kcs_chan", &chan);
+	if ((rc != 0) || (chan == 0 || chan > KCS_CHANNEL_MAX)) {
+		dev_err(dev, "no valid 'kcs_chan' configured\n");
+		return -ENODEV;
+	}
+
+	rc = of_property_read_u32(dev->of_node, "kcs_addr", &addr);
+	if (rc) {
+		dev_err(dev, "no valid 'kcs_addr' configured\n");
+		return -ENODEV;
+	}
+
+	kcs_bmc = kcs_bmc_alloc(dev, sizeof(*priv), chan);
+	if (!kcs_bmc)
+		return -ENOMEM;
+
+	priv = kcs_bmc_priv(kcs_bmc);
+	priv->map = syscon_node_to_regmap(dev->parent->of_node);
+	if (IS_ERR(priv->map)) {
+		dev_err(dev, "Couldn't get regmap\n");
+		return -ENODEV;
+	}
+
+	kcs_bmc->ioreg = ast_kcs_bmc_ioregs[chan - 1];
+	kcs_bmc->io_inputb = aspeed_kcs_inb;
+	kcs_bmc->io_outputb = aspeed_kcs_outb;
+
+	dev_set_drvdata(dev, kcs_bmc);
+
+	aspeed_kcs_set_address(kcs_bmc, addr);
+	aspeed_kcs_enable_channel(kcs_bmc, true);
+	rc = aspeed_kcs_config_irq(kcs_bmc, pdev);
+	if (rc)
+		return rc;
+
+	rc = misc_register(&kcs_bmc->miscdev);
+	if (rc) {
+		dev_err(dev, "Unable to register device\n");
+		return rc;
+	}
+
+	pr_info("channel=%u addr=0x%x idr=0x%x odr=0x%x str=0x%x\n",
+		chan, addr,
+		kcs_bmc->ioreg.idr, kcs_bmc->ioreg.odr, kcs_bmc->ioreg.str);
+
+	return 0;
+}
+
+static int aspeed_kcs_remove(struct platform_device *pdev)
+{
+	struct kcs_bmc *kcs_bmc = dev_get_drvdata(&pdev->dev);
+
+	misc_deregister(&kcs_bmc->miscdev);
+
+	return 0;
+}
+
+static const struct of_device_id ast_kcs_bmc_match[] = {
+	{ .compatible = "aspeed,ast2400-kcs-bmc" },
+	{ .compatible = "aspeed,ast2500-kcs-bmc" },
+	{ }
+};
+
+static struct platform_driver ast_kcs_bmc_driver = {
+	.driver = {
+		.name           = DEVICE_NAME,
+		.of_match_table = ast_kcs_bmc_match,
+	},
+	.probe = aspeed_kcs_probe,
+	.remove = aspeed_kcs_remove,
+};
+
+module_platform_driver(ast_kcs_bmc_driver);
+
+MODULE_DEVICE_TABLE(of, ast_kcs_bmc_match);
+MODULE_LICENSE("GPL v2");
+MODULE_AUTHOR("Haiyue Wang <[e-mail]>");
+MODULE_DESCRIPTION("Aspeed device interface to the KCS BMC device");