mfd: ls2kbmc: Introduce Loongson-2K BMC core driver

The Loongson-2K Board Management Controller provides an PCIe interface
to the host to access the feature implemented in the BMC.

The BMC is assembled on a server similar to the server machine with
Loongson-3 CPU. It supports multiple sub-devices like DRM and IPMI.

Co-developed-by: Chong Qiao <qiaochong@loongson.cn>
Signed-off-by: Chong Qiao <qiaochong@loongson.cn>
Reviewed-by: Huacai Chen <chenhuacai@loongson.cn>
Acked-by: Corey Minyard <corey@minyard.net>
Signed-off-by: Binbin Zhou <zhoubinbin@loongson.cn>
Link: https://lore.kernel.org/r/0dc1fd53020ce2562453961ffed2cd9eb8f359e1.1756987761.git.zhoubinbin@loongson.cn
Signed-off-by: Lee Jones <lee@kernel.org>

Author: AaronDot

MAINTAINERS

@@ -14417,6 +14417,12 @@ S:	Maintained
 F:	Documentation/devicetree/bindings/thermal/loongson,ls2k-thermal.yaml
 F:	drivers/thermal/loongson2_thermal.c
 
+LOONGSON-2K Board Management Controller (BMC) DRIVER
+M:	Binbin Zhou <zhoubinbin@loongson.cn>
+M:	Chong Qiao <qiaochong@loongson.cn>
+S:	Maintained
+F:	drivers/mfd/ls2k-bmc-core.c
+
 LOONGSON EDAC DRIVER
 M:	Zhao Qunqin <zhaoqunqin@loongson.cn>
 L:	linux-edac@vger.kernel.org

drivers/mfd/Kconfig

@@ -2480,6 +2480,19 @@ config MFD_LOONGSON_SE
 	  commands to the engine and must first send them to the controller,
 	  which will forward them to the corresponding engine.
 
+config MFD_LS2K_BMC_CORE
+	bool "Loongson-2K Board Management Controller Support"
+	depends on PCI && ACPI_GENERIC_GSI
+	select MFD_CORE
+	help
+	  Say yes here to add support for the Loongson-2K BMC which is a Board
+	  Management Controller connected to the PCIe bus. The device supports
+	  multiple sub-devices like display and IPMI. This driver provides common
+	  support for accessing the devices.
+
+	  The display is enabled by default in the driver, while the IPMI interface
+	  is enabled independently through the IPMI_LS2K option in the IPMI section.
+
 config MFD_QNAP_MCU
 	tristate "QNAP microcontroller unit core driver"
 	depends on SERIAL_DEV_BUS

drivers/mfd/Makefile

@@ -290,6 +290,8 @@ obj-$(CONFIG_MFD_INTEL_M10_BMC_CORE)   += intel-m10-bmc-core.o
 obj-$(CONFIG_MFD_INTEL_M10_BMC_SPI)    += intel-m10-bmc-spi.o
 obj-$(CONFIG_MFD_INTEL_M10_BMC_PMCI)   += intel-m10-bmc-pmci.o
 
+obj-$(CONFIG_MFD_LS2K_BMC_CORE)		+= ls2k-bmc-core.o
+
 obj-$(CONFIG_MFD_ATC260X)	+= atc260x-core.o
 obj-$(CONFIG_MFD_ATC260X_I2C)	+= atc260x-i2c.o
 

drivers/mfd/ls2k-bmc-core.c

@@ -0,0 +1,189 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Loongson-2K Board Management Controller (BMC) Core Driver.
+ *
+ * Copyright (C) 2024-2025 Loongson Technology Corporation Limited.
+ *
+ * Authors:
+ *	Chong Qiao <qiaochong@loongson.cn>
+ *	Binbin Zhou <zhoubinbin@loongson.cn>
+ */
+
+#include <linux/aperture.h>
+#include <linux/errno.h>
+#include <linux/init.h>
+#include <linux/kernel.h>
+#include <linux/mfd/core.h>
+#include <linux/module.h>
+#include <linux/pci.h>
+#include <linux/pci_ids.h>
+#include <linux/platform_data/simplefb.h>
+#include <linux/platform_device.h>
+
+/* LS2K BMC resources */
+#define LS2K_DISPLAY_RES_START		(SZ_16M + SZ_2M)
+#define LS2K_IPMI_RES_SIZE		0x1C
+#define LS2K_IPMI0_RES_START		(SZ_16M + 0xF00000)
+#define LS2K_IPMI1_RES_START		(LS2K_IPMI0_RES_START + LS2K_IPMI_RES_SIZE)
+#define LS2K_IPMI2_RES_START		(LS2K_IPMI1_RES_START + LS2K_IPMI_RES_SIZE)
+#define LS2K_IPMI3_RES_START		(LS2K_IPMI2_RES_START + LS2K_IPMI_RES_SIZE)
+#define LS2K_IPMI4_RES_START		(LS2K_IPMI3_RES_START + LS2K_IPMI_RES_SIZE)
+
+enum {
+	LS2K_BMC_DISPLAY,
+	LS2K_BMC_IPMI0,
+	LS2K_BMC_IPMI1,
+	LS2K_BMC_IPMI2,
+	LS2K_BMC_IPMI3,
+	LS2K_BMC_IPMI4,
+};
+
+static struct resource ls2k_display_resources[] = {
+	DEFINE_RES_MEM_NAMED(LS2K_DISPLAY_RES_START, SZ_4M, "simpledrm-res"),
+};
+
+static struct resource ls2k_ipmi0_resources[] = {
+	DEFINE_RES_MEM_NAMED(LS2K_IPMI0_RES_START, LS2K_IPMI_RES_SIZE, "ipmi0-res"),
+};
+
+static struct resource ls2k_ipmi1_resources[] = {
+	DEFINE_RES_MEM_NAMED(LS2K_IPMI1_RES_START, LS2K_IPMI_RES_SIZE, "ipmi1-res"),
+};
+
+static struct resource ls2k_ipmi2_resources[] = {
+	DEFINE_RES_MEM_NAMED(LS2K_IPMI2_RES_START, LS2K_IPMI_RES_SIZE, "ipmi2-res"),
+};
+
+static struct resource ls2k_ipmi3_resources[] = {
+	DEFINE_RES_MEM_NAMED(LS2K_IPMI3_RES_START, LS2K_IPMI_RES_SIZE, "ipmi3-res"),
+};
+
+static struct resource ls2k_ipmi4_resources[] = {
+	DEFINE_RES_MEM_NAMED(LS2K_IPMI4_RES_START, LS2K_IPMI_RES_SIZE, "ipmi4-res"),
+};
+
+static struct mfd_cell ls2k_bmc_cells[] = {
+	[LS2K_BMC_DISPLAY] = {
+		.name = "simple-framebuffer",
+		.num_resources = ARRAY_SIZE(ls2k_display_resources),
+		.resources = ls2k_display_resources
+	},
+	[LS2K_BMC_IPMI0] = {
+		.name = "ls2k-ipmi-si",
+		.num_resources = ARRAY_SIZE(ls2k_ipmi0_resources),
+		.resources = ls2k_ipmi0_resources
+	},
+	[LS2K_BMC_IPMI1] = {
+		.name = "ls2k-ipmi-si",
+		.num_resources = ARRAY_SIZE(ls2k_ipmi1_resources),
+		.resources = ls2k_ipmi1_resources
+	},
+	[LS2K_BMC_IPMI2] = {
+		.name = "ls2k-ipmi-si",
+		.num_resources = ARRAY_SIZE(ls2k_ipmi2_resources),
+		.resources = ls2k_ipmi2_resources
+	},
+	[LS2K_BMC_IPMI3] = {
+		.name = "ls2k-ipmi-si",
+		.num_resources = ARRAY_SIZE(ls2k_ipmi3_resources),
+		.resources = ls2k_ipmi3_resources
+	},
+	[LS2K_BMC_IPMI4] = {
+		.name = "ls2k-ipmi-si",
+		.num_resources = ARRAY_SIZE(ls2k_ipmi4_resources),
+		.resources = ls2k_ipmi4_resources
+	},
+};
+
+/*
+ * Currently the Loongson-2K BMC hardware does not have an I2C interface to adapt to the
+ * resolution. We set the resolution by presetting "video=1280x1024-16@2M" to the BMC memory.
+ */
+static int ls2k_bmc_parse_mode(struct pci_dev *pdev, struct simplefb_platform_data *pd)
+{
+	char *mode;
+	int depth, ret;
+
+	/* The last 16M of PCI BAR0 is used to store the resolution string. */
+	mode = devm_ioremap(&pdev->dev, pci_resource_start(pdev, 0) + SZ_16M, SZ_16M);
+	if (!mode)
+		return -ENOMEM;
+
+	/* The resolution field starts with the flag "video=". */
+	if (!strncmp(mode, "video=", 6))
+		mode = mode + 6;
+
+	ret = kstrtoint(strsep(&mode, "x"), 10, &pd->width);
+	if (ret)
+		return ret;
+
+	ret = kstrtoint(strsep(&mode, "-"), 10, &pd->height);
+	if (ret)
+		return ret;
+
+	ret = kstrtoint(strsep(&mode, "@"), 10, &depth);
+	if (ret)
+		return ret;
+
+	pd->stride = pd->width * depth / 8;
+	pd->format = depth == 32 ? "a8r8g8b8" : "r5g6b5";
+
+	return 0;
+}
+
+static int ls2k_bmc_probe(struct pci_dev *dev, const struct pci_device_id *id)
+{
+	struct simplefb_platform_data pd;
+	resource_size_t base;
+	int ret;
+
+	ret = pci_enable_device(dev);
+	if (ret)
+		return ret;
+
+	ret = ls2k_bmc_parse_mode(dev, &pd);
+	if (ret)
+		goto disable_pci;
+
+	ls2k_bmc_cells[LS2K_BMC_DISPLAY].platform_data = &pd;
+	ls2k_bmc_cells[LS2K_BMC_DISPLAY].pdata_size = sizeof(pd);
+	base = dev->resource[0].start + LS2K_DISPLAY_RES_START;
+
+	/* Remove conflicting efifb device */
+	ret = aperture_remove_conflicting_devices(base, SZ_4M, "simple-framebuffer");
+	if (ret) {
+		dev_err(&dev->dev, "Failed to removed firmware framebuffers: %d\n", ret);
+		goto disable_pci;
+	}
+
+	return devm_mfd_add_devices(&dev->dev, PLATFORM_DEVID_AUTO,
+				    ls2k_bmc_cells, ARRAY_SIZE(ls2k_bmc_cells),
+				    &dev->resource[0], 0, NULL);
+
+disable_pci:
+	pci_disable_device(dev);
+	return ret;
+}
+
+static void ls2k_bmc_remove(struct pci_dev *dev)
+{
+	pci_disable_device(dev);
+}
+
+static struct pci_device_id ls2k_bmc_devices[] = {
+	{ PCI_DEVICE(PCI_VENDOR_ID_LOONGSON, 0x1a05) },
+	{ }
+};
+MODULE_DEVICE_TABLE(pci, ls2k_bmc_devices);
+
+static struct pci_driver ls2k_bmc_driver = {
+	.name = "ls2k-bmc",
+	.id_table = ls2k_bmc_devices,
+	.probe = ls2k_bmc_probe,
+	.remove = ls2k_bmc_remove,
+};
+module_pci_driver(ls2k_bmc_driver);
+
+MODULE_DESCRIPTION("Loongson-2K Board Management Controller (BMC) Core driver");
+MODULE_AUTHOR("Loongson Technology Corporation Limited");
+MODULE_LICENSE("GPL");