ipmi: add an NPCM7xx KCS BMC driver

This driver exposes the Keyboard Controller Style (KCS) interface on
Novoton NPCM7xx SoCs as a character device. Such SOCs are commonly used
as a BaseBoard Management Controller (BMC) on a server board, and KCS
interface is commonly used to perform the in-band IPMI communication
between the server and its BMC.
Signed-off-by: Avi Fishman <avifishman70@gmail.com>
Signed-off-by: Haiyue Wang <haiyue.wang@linux.intel.com>
Signed-off-by: Corey Minyard <cminyard@mvista.com>

Documentation/devicetree/bindings/ipmi/npcm7xx-kcs-bmc.txt

+* Nuvoton NPCM7xx KCS (Keyboard Controller Style) IPMI interface
+
+The Nuvoton SOCs (NPCM7xx) 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
+    "nuvoton,npcm750-kcs-bmc"
+- interrupts : interrupt generated by the controller
+- kcs_chan : The KCS channel number in the controller
+
+Example:
+
+    lpc_kcs: lpc_kcs@f0007000 {
+        compatible = "nuvoton,npcm750-lpc-kcs", "simple-mfd", "syscon";
+        reg = <0xf0007000 0x40>;
+        reg-io-width = <1>;
+
+        #address-cells = <1>;
+        #size-cells = <1>;
+        ranges = <0x0 0xf0007000 0x40>;
+
+        kcs1: kcs1@0 {
+            compatible = "nuvoton,npcm750-kcs-bmc";
+            reg = <0x0 0x40>;
+            interrupts = <0 9 4>;
+            kcs_chan = <1>;
+            status = "disabled";
+        };
+
+        kcs2: kcs2@0 {
+            compatible = "nuvoton,npcm750-kcs-bmc";
+            reg = <0x0 0x40>;
+            interrupts = <0 9 4>;
+            kcs_chan = <2>;
+            status = "disabled";
+        };
+    };
\ No newline at end of file

drivers/char/ipmi/Kconfig

@@ -111,6 +111,21 @@ config ASPEED_KCS_IPMI_BMC
 	  The driver implements the BMC side of the KCS contorller, it
 	  provides the access of KCS IO space for BMC side.
 
+config NPCM7XX_KCS_IPMI_BMC
+	depends on ARCH_NPCM7XX || COMPILE_TEST
+	select IPMI_KCS_BMC
+	select REGMAP_MMIO
+	tristate "NPCM7xx KCS IPMI BMC driver"
+	help
+	  Provides a driver for the KCS (Keyboard Controller Style) IPMI
+	  interface found on Nuvoton NPCM7xx SOCs.
+
+	  The driver implements the BMC side of the KCS contorller, it
+	  provides the access of KCS IO space for BMC side.
+
+	  This support is also available as a module.  If so, the module
+	  will be called kcs_bmc_npcm7xx.
+
 config ASPEED_BT_IPMI_BMC
 	depends on ARCH_ASPEED || COMPILE_TEST
        depends on REGMAP && REGMAP_MMIO && MFD_SYSCON

drivers/char/ipmi/Makefile

@@ -24,3 +24,4 @@ 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
+obj-$(CONFIG_NPCM7XX_KCS_IPMI_BMC) += kcs_bmc_npcm7xx.o

drivers/char/ipmi/kcs_bmc_npcm7xx.c

+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (c) 2018, Nuvoton Corporation.
+ * Copyright (c) 2018, Intel Corporation.
+ */
+
+#define pr_fmt(fmt) "nuvoton-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/regmap.h>
+#include <linux/slab.h>
+
+#include "kcs_bmc.h"
+
+#define DEVICE_NAME	"npcm-kcs-bmc"
+#define KCS_CHANNEL_MAX	3
+
+#define KCS1ST		0x0C
+#define KCS2ST		0x1E
+#define KCS3ST		0x30
+
+#define KCS1DO		0x0E
+#define KCS2DO		0x20
+#define KCS3DO		0x32
+
+#define KCS1DI		0x10
+#define KCS2DI		0x22
+#define KCS3DI		0x34
+
+#define KCS1CTL		0x18
+#define KCS2CTL		0x2A
+#define KCS3CTL		0x3C
+#define    KCS_CTL_IBFIE	BIT(0)
+
+/*
+ * 7.2.4 Core KCS Registers
+ * Registers in this module are 8 bits. An 8-bit register must be accessed
+ * by an 8-bit read or write.
+ *
+ * sts: KCS Channel n Status Register (KCSnST).
+ * dob: KCS Channel n Data Out Buffer Register (KCSnDO).
+ * dib: KCS Channel n Data In Buffer Register (KCSnDI).
+ * ctl: KCS Channel n Control Register (KCSnCTL).
+ */
+struct npcm7xx_kcs_reg {
+	u32 sts;
+	u32 dob;
+	u32 dib;
+	u32 ctl;
+};
+
+struct npcm7xx_kcs_bmc {
+	struct regmap *map;
+
+	const struct npcm7xx_kcs_reg *reg;
+};
+
+static const struct npcm7xx_kcs_reg npcm7xx_kcs_reg_tbl[KCS_CHANNEL_MAX] = {
+	{ .sts = KCS1ST, .dob = KCS1DO, .dib = KCS1DI, .ctl = KCS1CTL },
+	{ .sts = KCS2ST, .dob = KCS2DO, .dib = KCS2DI, .ctl = KCS2CTL },
+	{ .sts = KCS3ST, .dob = KCS3DO, .dib = KCS3DI, .ctl = KCS3CTL },
+};
+
+static u8 npcm7xx_kcs_inb(struct kcs_bmc *kcs_bmc, u32 reg)
+{
+	struct npcm7xx_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 npcm7xx_kcs_outb(struct kcs_bmc *kcs_bmc, u32 reg, u8 data)
+{
+	struct npcm7xx_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);
+}
+
+static void npcm7xx_kcs_enable_channel(struct kcs_bmc *kcs_bmc, bool enable)
+{
+	struct npcm7xx_kcs_bmc *priv = kcs_bmc_priv(kcs_bmc);
+
+	regmap_update_bits(priv->map, priv->reg->ctl, KCS_CTL_IBFIE,
+			   enable ? KCS_CTL_IBFIE : 0);
+}
+
+static irqreturn_t npcm7xx_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 npcm7xx_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, npcm7xx_kcs_irq, IRQF_SHARED,
+				dev_name(dev), kcs_bmc);
+}
+
+static int npcm7xx_kcs_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct npcm7xx_kcs_bmc *priv;
+	struct kcs_bmc *kcs_bmc;
+	u32 chan;
+	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;
+	}
+
+	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;
+	}
+	priv->reg = &npcm7xx_kcs_reg_tbl[chan - 1];
+
+	kcs_bmc->ioreg.idr = priv->reg->dib;
+	kcs_bmc->ioreg.odr = priv->reg->dob;
+	kcs_bmc->ioreg.str = priv->reg->sts;
+	kcs_bmc->io_inputb = npcm7xx_kcs_inb;
+	kcs_bmc->io_outputb = npcm7xx_kcs_outb;
+
+	dev_set_drvdata(dev, kcs_bmc);
+
+	npcm7xx_kcs_enable_channel(kcs_bmc, true);
+	rc = npcm7xx_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 idr=0x%x odr=0x%x str=0x%x\n",
+		chan,
+		kcs_bmc->ioreg.idr, kcs_bmc->ioreg.odr, kcs_bmc->ioreg.str);
+
+	return 0;
+}
+
+static int npcm7xx_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 npcm_kcs_bmc_match[] = {
+	{ .compatible = "nuvoton,npcm750-kcs-bmc" },
+	{ }
+};
+MODULE_DEVICE_TABLE(of, npcm_kcs_bmc_match);
+
+static struct platform_driver npcm_kcs_bmc_driver = {
+	.driver = {
+		.name		= DEVICE_NAME,
+		.of_match_table	= npcm_kcs_bmc_match,
+	},
+	.probe	= npcm7xx_kcs_probe,
+	.remove	= npcm7xx_kcs_remove,
+};
+module_platform_driver(npcm_kcs_bmc_driver);
+
+MODULE_LICENSE("GPL v2");
+MODULE_AUTHOR("Avi Fishman <avifishman70@gmail.com>");
+MODULE_AUTHOR("Haiyue Wang <haiyue.wang@linux.intel.com>");
+MODULE_DESCRIPTION("NPCM7xx device interface to the KCS BMC device");