This patch adds Loongson-2K BMC IPMI support.

According to the existing design, we use software simulation to
implement the KCS interface registers: Stauts/Command/Data_Out/Data_In.

Also since both host side and BMC side read and write kcs status, I use
fifo pointer to ensure data consistency.

Therefore I made the whole IPMI driver independent.

Co-developed-by: Chong Qiao <qiaoch...@loongson.cn>
Signed-off-by: Chong Qiao <qiaoch...@loongson.cn>
Signed-off-by: Binbin Zhou <zhoubin...@loongson.cn>
---
 drivers/char/ipmi/Makefile       |   1 +
 drivers/char/ipmi/ipmi_si.h      |   8 +
 drivers/char/ipmi/ipmi_si_intf.c |   3 +
 drivers/char/ipmi/ipmi_si_ls2k.c | 250 +++++++++++++++++++++++++++++++
 4 files changed, 262 insertions(+)
 create mode 100644 drivers/char/ipmi/ipmi_si_ls2k.c

diff --git a/drivers/char/ipmi/Makefile b/drivers/char/ipmi/Makefile
index e0944547c9d0..614be45863b4 100644
--- a/drivers/char/ipmi/Makefile
+++ b/drivers/char/ipmi/Makefile
@@ -7,6 +7,7 @@ ipmi_si-y := ipmi_si_intf.o ipmi_kcs_sm.o ipmi_smic_sm.o 
ipmi_bt_sm.o \
        ipmi_si_hotmod.o ipmi_si_hardcode.o ipmi_si_platform.o \
        ipmi_si_mem_io.o
 ipmi_si-$(CONFIG_HAS_IOPORT) += ipmi_si_port_io.o
+ipmi_si-$(CONFIG_LOONGARCH) += ipmi_si_ls2k.o
 ipmi_si-$(CONFIG_PCI) += ipmi_si_pci.o
 ipmi_si-$(CONFIG_PARISC) += ipmi_si_parisc.o
 
diff --git a/drivers/char/ipmi/ipmi_si.h b/drivers/char/ipmi/ipmi_si.h
index a7ead2a4c753..0a4af352a42c 100644
--- a/drivers/char/ipmi/ipmi_si.h
+++ b/drivers/char/ipmi/ipmi_si.h
@@ -101,6 +101,14 @@ static inline void ipmi_si_parisc_init(void) { }
 static inline void ipmi_si_parisc_shutdown(void) { }
 #endif
 
+#ifdef CONFIG_LOONGARCH
+void ipmi_si_ls2k_init(void);
+void ipmi_si_ls2k_shutdown(void);
+#else
+static inline void ipmi_si_ls2k_init(void) { }
+static inline void ipmi_si_ls2k_shutdown(void) { }
+#endif
+
 int ipmi_si_port_setup(struct si_sm_io *io);
 int ipmi_si_mem_setup(struct si_sm_io *io);
 
diff --git a/drivers/char/ipmi/ipmi_si_intf.c b/drivers/char/ipmi/ipmi_si_intf.c
index eea23a3b966e..7227bc61be79 100644
--- a/drivers/char/ipmi/ipmi_si_intf.c
+++ b/drivers/char/ipmi/ipmi_si_intf.c
@@ -2108,6 +2108,7 @@ static int __init init_ipmi_si(void)
        ipmi_si_pci_init();
 
        ipmi_si_parisc_init();
+       ipmi_si_ls2k_init();
 
        /* We prefer devices with interrupts, but in the case of a machine
           with multiple BMCs we assume that there will be several instances
@@ -2292,6 +2293,8 @@ static void cleanup_ipmi_si(void)
 
        ipmi_si_platform_shutdown();
 
+       ipmi_si_ls2k_shutdown();
+
        mutex_lock(&smi_infos_lock);
        list_for_each_entry_safe(e, tmp_e, &smi_infos, link)
                cleanup_one_si(e);
diff --git a/drivers/char/ipmi/ipmi_si_ls2k.c b/drivers/char/ipmi/ipmi_si_ls2k.c
new file mode 100644
index 000000000000..cb31bb989fca
--- /dev/null
+++ b/drivers/char/ipmi/ipmi_si_ls2k.c
@@ -0,0 +1,250 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Driver for Loongson-2K BMC IPMI
+ *
+ * Copyright (C) 2024 Loongson Technology Corporation Limited.
+ *
+ * Originally written by Chong Qiao <qiaoch...@loongson.cn>
+ * Rewritten for mainline by Binbin Zhou <zhoubin...@loongson.cn>
+ */
+
+#include <linux/ioport.h>
+#include <linux/module.h>
+#include <linux/types.h>
+
+#include "ipmi_si.h"
+
+#define LS2K_KCS_STS_OBF       BIT(0)
+#define LS2K_KCS_STS_IBF       BIT(1)
+#define LS2K_KCS_STS_SMS_ATN   BIT(2)
+#define LS2K_KCS_STS_CMD       BIT(3)
+
+#define LS2K_KCS_DATA_MASK     (LS2K_KCS_STS_OBF | LS2K_KCS_STS_IBF | 
LS2K_KCS_STS_CMD)
+
+/* Read and write fifo pointers for data consistency. */
+struct ls2k_fifo_flag {
+       u8 ibfh;
+       u8 ibft;
+       u8 obfh;
+       u8 obft;
+};
+
+struct ls2k_kcs_reg {
+       u8 status;
+       u8 data_out;
+       s16 data_in;
+       s16 cmd;
+};
+
+struct ls2k_kcs_data {
+       struct ls2k_fifo_flag fifo;
+       struct ls2k_kcs_reg reg;
+       u8 cmd_data;
+       u8 version;
+       u32 write_req;
+       u32 write_ack;
+       u32 reserved[2];
+};
+
+static void ls2k_set_obf(struct ls2k_kcs_data *ik, u8 sts)
+{
+       ik->reg.status = (ik->reg.status & ~LS2K_KCS_STS_OBF) | (sts & BIT(0));
+}
+
+static void ls2k_set_ibf(struct ls2k_kcs_data *ik, u8 sts)
+{
+       ik->reg.status = (ik->reg.status & ~LS2K_KCS_STS_IBF) | ((sts & BIT(0)) 
<< 1);
+}
+
+static u8 ls2k_get_ibf(struct ls2k_kcs_data *ik)
+{
+       return (ik->reg.status >> 1) & BIT(0);
+}
+
+static unsigned char intf_sim_inb_v0(struct ls2k_kcs_data *ik,
+                                    unsigned int offset)
+{
+       u32 inb = 0;
+
+       switch (offset & BIT(0)) {
+       case 0:
+               inb = ik->reg.data_out;
+               ls2k_set_obf(ik, 0);
+               break;
+       case 1:
+               inb = ik->reg.status;
+               break;
+       }
+
+       return inb;
+}
+
+static unsigned char intf_sim_inb_v1(struct ls2k_kcs_data *ik,
+                                    unsigned int offset)
+{
+       u32 inb = 0;
+       int cmd;
+       bool obf, ibf;
+
+       obf = ik->fifo.obfh != ik->fifo.obft;
+       ibf = ik->fifo.ibfh != ik->fifo.ibft;
+       cmd = ik->cmd_data;
+
+       switch (offset & BIT(0)) {
+       case 0:
+               inb = ik->reg.data_out;
+               ik->fifo.obft = ik->fifo.obfh;
+               break;
+       case 1:
+               inb = ik->reg.status & ~LS2K_KCS_DATA_MASK;
+               inb |= obf | (ibf << 1) | (cmd << 3);
+               break;
+       }
+
+       return inb;
+}
+
+static unsigned char ls2k_mem_inb(const struct si_sm_io *io,
+                                 unsigned int offset)
+{
+       struct ls2k_kcs_data *ik = io->addr;
+       int inb = 0;
+
+       if (ik->version == 0)
+               inb = intf_sim_inb_v0(ik, offset);
+       else if (ik->version == 1)
+               inb = intf_sim_inb_v1(ik, offset);
+
+       return inb;
+}
+
+static void intf_sim_outb_v0(struct ls2k_kcs_data *ik, unsigned int offset,
+                            unsigned char val)
+{
+       if (ls2k_get_ibf(ik))
+               return;
+
+       switch (offset & BIT(0)) {
+       case 0:
+               ik->reg.data_in = val;
+               ik->reg.status &= ~LS2K_KCS_STS_CMD;
+               break;
+
+       case 1:
+               ik->reg.cmd = val;
+               ik->reg.status |= LS2K_KCS_STS_CMD;
+               break;
+       }
+
+       ls2k_set_ibf(ik, 1);
+       ik->write_req++;
+}
+
+static void intf_sim_outb_v1(struct ls2k_kcs_data *ik, unsigned int offset,
+                            unsigned char val)
+{
+       if (ik->fifo.ibfh != ik->fifo.ibft)
+               return;
+
+       switch (offset & BIT(0)) {
+       case 0:
+               ik->reg.data_in = val;
+               ik->cmd_data = 0;
+               break;
+
+       case 1:
+               ik->reg.cmd = val;
+               ik->cmd_data = 1;
+               break;
+       }
+
+       ik->fifo.ibfh = !ik->fifo.ibft;
+       ik->write_req++;
+}
+
+static void ls2k_mem_outb(const struct si_sm_io *io, unsigned int offset,
+                         unsigned char val)
+{
+       struct ls2k_kcs_data *ik = io->addr;
+
+       if (ik->version == 0)
+               intf_sim_outb_v0(ik, offset, val);
+       else if (ik->version == 1)
+               intf_sim_outb_v1(ik, offset, val);
+}
+
+static void ls2k_mem_cleanup(struct si_sm_io *io)
+{
+       if (io->addr)
+               iounmap(io->addr);
+}
+
+static int ipmi_ls2k_sim_setup(struct si_sm_io *io)
+{
+       io->addr = ioremap(io->addr_data, io->regspacing);
+       if (!io->addr)
+               return -EIO;
+
+       io->inputb = ls2k_mem_inb;
+       io->outputb = ls2k_mem_outb;
+       io->io_cleanup = ls2k_mem_cleanup;
+
+       return 0;
+}
+
+static int ipmi_ls2k_probe(struct platform_device *pdev)
+{
+       struct si_sm_io io;
+
+       dev_info(&pdev->dev, "probing via ls2k platform");
+       memset(&io, 0, sizeof(io));
+
+       io.addr_source  = SI_PLATFORM;
+       io.si_type      = SI_KCS;
+       io.addr_space   = IPMI_MEM_ADDR_SPACE;
+       io.io_setup     = ipmi_ls2k_sim_setup;
+       io.addr_data    = pdev->resource[0].start;
+       io.regspacing   = pdev->resource[0].end - pdev->resource[0].start + 1;
+       io.regsize      = DEFAULT_REGSIZE;
+       io.regshift     = 0;
+       io.dev          = &pdev->dev;
+       io.irq          = 0;
+       if (io.irq)
+               io.irq_setup = ipmi_std_irq_setup;
+
+       dev_info(&pdev->dev, "%pR regsize %d spacing %d irq %d\n",
+                &pdev->resource[0], io.regsize, io.regspacing, io.irq);
+
+       return ipmi_si_add_smi(&io);
+}
+
+static void ipmi_ls2k_remove(struct platform_device *pdev)
+{
+       ipmi_si_remove_by_dev(&pdev->dev);
+}
+
+struct platform_driver ipmi_ls2k_platform_driver = {
+       .driver = {
+               .name = "ls2k-ipmi-si",
+       },
+       .probe  = ipmi_ls2k_probe,
+       .remove = ipmi_ls2k_remove,
+};
+
+static bool platform_registered;
+void ipmi_si_ls2k_init(void)
+{
+       int rv;
+
+       rv = platform_driver_register(&ipmi_ls2k_platform_driver);
+       if (rv)
+               pr_err("Unable to register driver: %d\n", rv);
+       else
+               platform_registered = true;
+}
+
+void ipmi_si_ls2k_shutdown(void)
+{
+       if (platform_registered)
+               platform_driver_unregister(&ipmi_ls2k_platform_driver);
+}
-- 
2.43.5

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