[PATCH v1] eSPI: add Aspeed AST2500 eSPI driver to boot a host with PCH runs on eSPI

[Haiyue Wang <haiyue.wang@linux.intel.com>]

When PCH works under eSPI mode, the PMC (Power Management Controller) in
PCH is waiting for SUS_ACK from BMC after it alerts SUS_WARN. It is in
dead loop if no SUS_ACK assert. This is the basic requirement for the BMC
works as eSPI slave.

Also for the host power on / off actions, from BMC side, the following VW
(Virtual Wire) messages are done in firmware:
1. SLAVE_BOOT_LOAD_DONE / SLAVE_BOOT_LOAD_STATUS
2. SUS_ACK
3. OOB_RESET_ACK
4. HOST_RESET_ACK

Signed-off-by: Haiyue Wang <haiyue.wang@linux.intel.com>
---
 .../devicetree/bindings/misc/aspeed-espi-slave.txt |  20 ++
 Documentation/misc-devices/espi-slave.rst          | 114 +++++++++
 drivers/misc/Kconfig                               |  11 +
 drivers/misc/Makefile                              |   1 +
 drivers/misc/aspeed-espi-slave.c                   | 266 +++++++++++++++++++++
 5 files changed, 412 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/misc/aspeed-espi-slave.txt
 create mode 100644 Documentation/misc-devices/espi-slave.rst
 create mode 100644 drivers/misc/aspeed-espi-slave.c

diff --git a/Documentation/devicetree/bindings/misc/aspeed-espi-slave.txt b/Documentation/devicetree/bindings/misc/aspeed-espi-slave.txt
new file mode 100644
index 0000000..35da26f
--- /dev/null
+++ b/Documentation/devicetree/bindings/misc/aspeed-espi-slave.txt
@@ -0,0 +1,20 @@
+Aspeed eSPI Slave Controller
+
+Required properties:
+ - compatible: must be one of:
+	- "aspeed,ast2500-espi-slave"
+
+ - reg: physical base address of the controller and length of memory mapped
+   region
+
+ - interrupts: interrupt generated by the controller
+
+Example:
+
+    espi: espi@1e6ee000 {
+        compatible = "aspeed,ast2500-espi-slave";
+        reg = <0x1e6ee000 0x100>;
+        interrupts = <23>;
+        status = "disabled";
+};
+
diff --git a/Documentation/misc-devices/espi-slave.rst b/Documentation/misc-devices/espi-slave.rst
new file mode 100644
index 0000000..405b619
--- /dev/null
+++ b/Documentation/misc-devices/espi-slave.rst
@@ -0,0 +1,114 @@
+eSPI Slave
+==========
+
+The PCH (**eSPI master**) provides the eSPI to support connection of a
+BMC (**eSPI slave**) to the platform.
+
+The LPC and eSPI interfaces are mutually exclusive. Both use the same
+pins, but on power-up, a HW strap determines if the eSPI or the LPC bus
+is operational. Once selected, it’s not possible to change to the other
+interface.
+
+``eSPI Channels and Supported Transactions``
+ +------+---------------------+----------------------+--------------------+
+ | CH # | Channel             | Posted Cycles        | Non-Posted Cycles  |
+ +======+=====================+======================+====================+
+ |  0   | Peripheral          | Memory Write,        | Memory Read,       |
+ |      |                     | Completions          | I/O Read/Write     |
+ +------+---------------------+----------------------+--------------------+
+ |  1   | Virtual Wire        | Virtual Wire GET/PUT | N/A                |
+ +------+---------------------+----------------------+--------------------+
+ |  2   | Out-of-Band Message | SMBus Packet GET/PUT | N/A                |
+ +------+---------------------+----------------------+--------------------+
+ |  3   | Flash Access        | N/A                  | Flash Read, Write, |
+ |      |                     |                      | Erase              |
+ +------+---------------------+----------------------+--------------------+
+ |  N/A | General             | Register Accesses    | N/A                |
+ +------+---------------------+----------------------+--------------------+
+
+Virtual Wire Channel (Channel 1) Overview
+-----------------------------------------
+
+The Virtual Wire channel uses a standard message format to communicate
+several types of signals between the components on the platform::
+
+ - Sideband and GPIO Pins: System events and other dedicated signals
+   between the PCH and eSPI slave. These signals are tunneled between the
+   two components over eSPI.
+
+ - Serial IRQ Interrupts: Interrupts are tunneled from the eSPI slave to
+   the PCH. Both edge and triggered interrupts are supported.
+
+When PCH runs on eSPI mode, from BMC side, the following VW messages are
+done in firmware::
+
+ 1. SLAVE_BOOT_LOAD_DONE / SLAVE_BOOT_LOAD_STATUS
+ 2. SUS_ACK
+ 3. OOB_RESET_ACK
+ 4. HOST_RESET_ACK
+
+``eSPI Virtual Wires (VW)``
+ +----------------------+---------+---------------------------------------+
+ |Virtual Wire          |PCH Pin  |Comments                               |
+ |                      |Direction|                                       |
+ +======================+=========+=======================================+
+ |SUS_WARN#             |Output   |PCH pin is a GPIO when eSPI is enabled.|
+ |                      |         |eSPI controller receives as VW message.|
+ +----------------------+---------+---------------------------------------+
+ |SUS_ACK#              |Input    |PCH pin is a GPIO when eSPI is enabled.|
+ |                      |         |eSPI controller receives as VW message.|
+ +----------------------+---------+---------------------------------------+
+ |SLAVE_BOOT_LOAD_DONE  |Input    |Sent when the BMC has completed its    |
+ |                      |         |boot process as an indication to       |
+ |                      |         |eSPI-MC to continue with the G3 to S0  |
+ |                      |         |exit.                                  |
+ |                      |         |The eSPI Master waits for the assertion|
+ |                      |         |of this virtual wire before proceeding |
+ |                      |         |with the SLP_S5# deassertion.          |
+ |                      |         |The intent is that it is never changed |
+ |                      |         |except on a G3 exit - it is reset on a |
+ |                      |         |G3 entry.                              |
+ +----------------------+---------+---------------------------------------+
+ |SLAVE_BOOT_LOAD_STATUS|Input    |Sent upon completion of the Slave Boot |
+ |                      |         |Load from the attached flash. A stat of|
+ |                      |         |1 indicates that the boot code load was|
+ |                      |         |successful and that the integrity of   |
+ |                      |         |the image is intact.                   |
+ +----------------------+---------+---------------------------------------+
+ |HOST_RESET_WARN       |Output   |Sent from the MC just before the Host  |
+ |                      |         |is about to enter reset. Upon receiving|
+ |                      |         |, the BMC must flush and quiesce its   |
+ |                      |         |upstream Peripheral Channel request    |
+ |                      |         |queues and assert HOST_RESET_ACK VWire.|
+ |                      |         |The MC subsequently completes any      |
+ |                      |         |outstanding posted transactions or     |
+ |                      |         |completions and then disables the      |
+ |                      |         |Peripheral Channel via a write to      |
+ |                      |         |the Slave's Configuration Register.    |
+ +----------------------+---------+---------------------------------------+
+ |HOST_RESET_ACK        |Input    |ACK for the HOST_RESET_WARN message    |
+ +----------------------+---------+---------------------------------------+
+ |OOB_RESET_WARN        |Output   |Sent from the MC just before the OOB   |
+ |                      |         |processor is about to enter reset. Upon|
+ |                      |         |receiving, the BMC must flush and      |
+ |                      |         |quiesce its OOB Channel upstream       |
+ |                      |         |request queues and assert OOB_RESET_ACK|
+ |                      |         |VWire. The-MC subsequently completes   |
+ |                      |         |any outstanding posted transactions or |
+ |                      |         |completions and then disables the OOB  |
+ |                      |         |Channel via a write to the Slave's     |
+ |                      |         |Configuration Register.                |
+ +----------------------+---------+---------------------------------------+
+ |OOB_RESET_ACK         |Input    |ACK for OOB_RESET_WARN message         |
+ +----------------------+---------+---------------------------------------+
+
+`Intel C620 Series Chipset Platform Controller Hub
+<https://www.intel.com/content/www/us/en/chipsets/c620-series-chipset-datasheet.html>`_
+
+   -- 17. Enhanced Serial Peripheral Interface
+
+
+`Enhanced Serial Peripheral Interface (eSPI)
+- Interface Base Specification (for Client and Server Platforms)
+<https://www.intel.com/content/dam/support/us/en/documents/software/chipset-software/327432-004_espi_base_specification_rev1.0.pdf>`_
+
diff --git a/drivers/misc/Kconfig b/drivers/misc/Kconfig
index f1a5c23..fec5783 100644
--- a/drivers/misc/Kconfig
+++ b/drivers/misc/Kconfig
@@ -471,6 +471,17 @@ config VEXPRESS_SYSCFG
 	  ARM Ltd. Versatile Express uses specialised platform configuration
 	  bus. System Configuration interface is one of the possible means
 	  of generating transactions on this bus.
+config ASPEED_ESPI_SLAVE
+	depends on ARCH_ASPEED || COMPILE_TEST
+	select REGMAP_MMIO
+	tristate "Aspeed ast2500 eSPI slave device"
+	---help---
+	  This allows host to access Baseboard Management Controller (BMC) over the
+	  Enhanced Serial Peripheral Interface (eSPI) bus, which replaces the Low Pin
+	  Count (LPC) bus.
+
+	  Its interface supports peripheral, virtual wire, out-of-band, and flash
+	  sharing channels.
 
 config ASPEED_LPC_CTRL
 	depends on (ARCH_ASPEED || COMPILE_TEST) && REGMAP && MFD_SYSCON
diff --git a/drivers/misc/Makefile b/drivers/misc/Makefile
index 5ca5f64..a1081f4 100644
--- a/drivers/misc/Makefile
+++ b/drivers/misc/Makefile
@@ -52,6 +52,7 @@ obj-$(CONFIG_GENWQE)		+= genwqe/
 obj-$(CONFIG_ECHO)		+= echo/
 obj-$(CONFIG_VEXPRESS_SYSCFG)	+= vexpress-syscfg.o
 obj-$(CONFIG_CXL_BASE)		+= cxl/
+obj-$(CONFIG_ASPEED_ESPI_SLAVE) += aspeed-espi-slave.o
 obj-$(CONFIG_ASPEED_LPC_CTRL)	+= aspeed-lpc-ctrl.o
 obj-$(CONFIG_ASPEED_LPC_SNOOP)	+= aspeed-lpc-snoop.o
 obj-$(CONFIG_PCI_ENDPOINT_TEST)	+= pci_endpoint_test.o
diff --git a/drivers/misc/aspeed-espi-slave.c b/drivers/misc/aspeed-espi-slave.c
new file mode 100644
index 0000000..a0359cb
--- /dev/null
+++ b/drivers/misc/aspeed-espi-slave.c
@@ -0,0 +1,266 @@
+// SPDX-License-Identifier: GPL-2.0
+// Copyright (C) 2012-2020, ASPEED Technology Inc.
+// Copyright (c) 2015-2017, Intel Corporation.
+
+#include <linux/atomic.h>
+#include <linux/errno.h>
+#include <linux/interrupt.h>
+#include <linux/io.h>
+#include <linux/miscdevice.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>
+
+#define DEVICE_NAME     "aspeed-espi-slave"
+
+
+#define ESPI_CTRL                 0x00
+#define      ESPI_CTRL_SW_RESET             GENMASK(31, 24)
+#define      ESPI_CTRL_OOB_CHRDY            BIT(4)
+#define ESPI_ISR                  0x08
+#define      ESPI_ISR_HW_RESET              BIT(31)
+#define      ESPI_ISR_VW_SYS_EVT1           BIT(22)
+#define      ESPI_ISR_VW_SYS_EVT            BIT(8)
+#define ESPI_IER                  0x0C
+
+#define ESPI_SYS_IER              0x94
+#define ESPI_SYS_EVENT            0x98
+#define ESPI_SYS_INT_T0           0x110
+#define ESPI_SYS_INT_T1           0x114
+#define ESPI_SYS_INT_T2           0x118
+#define ESPI_SYS_ISR              0x11C
+#define      ESPI_SYSEVT_HOST_RST_ACK       BIT(27)
+#define      ESPI_SYSEVT_SLAVE_BOOT_STATUS  BIT(23)
+#define      ESPI_SYSEVT_SLAVE_BOOT_DONE    BIT(20)
+#define      ESPI_SYSEVT_OOB_RST_ACK        BIT(16)
+#define      ESPI_SYSEVT_HOST_RST_WARN      BIT(8)
+#define      ESPI_SYSEVT_OOB_RST_WARN       BIT(6)
+#define      ESPI_SYSEVT_PLT_RST_N          BIT(5)
+
+#define ESPI_SYS1_IER             0x100
+#define ESPI_SYS1_EVENT           0x104
+#define ESPI_SYS1_INT_T0          0x120
+#define ESPI_SYS1_INT_T1          0x124
+#define ESPI_SYS1_INT_T2          0x128
+#define ESPI_SYS1_ISR             0x12C
+#define      ESPI_SYSEVT1_SUS_ACK           BIT(20)
+#define      ESPI_SYSEVT1_SUS_WARN          BIT(0)
+
+
+struct aspeed_espi_slave_data {
+	struct regmap *map;
+};
+
+static void aspeed_espi_slave_sys_event(struct aspeed_espi_slave_data *priv)
+{
+	u32 sts, evt;
+
+	if (regmap_read(priv->map, ESPI_SYS_ISR, &sts) != 0 ||
+	    regmap_read(priv->map, ESPI_SYS_EVENT, &evt) != 0)
+		return;
+
+	if (sts & ESPI_SYSEVT_HOST_RST_WARN)
+		regmap_update_bits_base(priv->map, ESPI_SYS_EVENT,
+			ESPI_SYSEVT_HOST_RST_ACK,
+			evt & ESPI_SYSEVT_HOST_RST_WARN ?
+				ESPI_SYSEVT_HOST_RST_ACK : 0,
+			NULL, false, true);
+
+	if (sts & ESPI_SYSEVT_OOB_RST_WARN)
+		regmap_update_bits_base(priv->map, ESPI_SYS_EVENT,
+			ESPI_SYSEVT_OOB_RST_ACK,
+			evt & ESPI_SYSEVT_OOB_RST_WARN ?
+				ESPI_SYSEVT_OOB_RST_ACK : 0,
+			NULL, false, true);
+
+	regmap_write(priv->map, ESPI_SYS_ISR, sts);
+}
+
+static void aspeed_espi_slave_sys1_event(struct aspeed_espi_slave_data *priv)
+{
+	u32 sts;
+
+	if (regmap_read(priv->map, ESPI_SYS1_ISR, &sts) != 0)
+		return;
+
+	if (sts & ESPI_SYSEVT1_SUS_WARN)
+		regmap_update_bits_base(priv->map, ESPI_SYS1_EVENT,
+			ESPI_SYSEVT1_SUS_ACK, ESPI_SYSEVT1_SUS_ACK,
+			NULL, false, true);
+
+	regmap_write(priv->map, ESPI_SYS1_ISR, sts);
+}
+
+static irqreturn_t aspeed_espi_slave_irq(int irq, void *arg)
+{
+	struct aspeed_espi_slave_data *priv = arg;
+	u32 sts;
+
+	if (regmap_read(priv->map, ESPI_ISR, &sts) != 0)
+		return IRQ_NONE;
+
+	if (sts & ESPI_ISR_HW_RESET) {
+		regmap_update_bits_base(priv->map, ESPI_CTRL,
+				ESPI_CTRL_SW_RESET, 0,
+				NULL, false, true);
+		regmap_update_bits_base(priv->map, ESPI_CTRL,
+				ESPI_CTRL_SW_RESET, ESPI_CTRL_SW_RESET,
+				NULL, false, true);
+
+		regmap_update_bits_base(priv->map, ESPI_SYS_EVENT,
+				ESPI_SYSEVT_SLAVE_BOOT_STATUS |
+					ESPI_SYSEVT_SLAVE_BOOT_DONE,
+				ESPI_SYSEVT_SLAVE_BOOT_STATUS |
+					ESPI_SYSEVT_SLAVE_BOOT_DONE,
+				NULL, false, true);
+	}
+
+	if (sts & ESPI_ISR_VW_SYS_EVT)
+		aspeed_espi_slave_sys_event(priv);
+
+	if (sts & ESPI_ISR_VW_SYS_EVT1)
+		aspeed_espi_slave_sys1_event(priv);
+
+	regmap_write(priv->map, ESPI_ISR, sts);
+
+	return IRQ_HANDLED;
+}
+
+
+/* Setup Interrupt Type/Enable of System Event from Master
+ *				   T2 T1 T0
+ *  1). HOST_RST_WARN : Dual Edge   1  0  0
+ *  2). OOB_RST_WARN  : Dual Edge   1  0  0
+ *  3). PLTRST_N      : Dual Edge   1  0  0
+ */
+#define ESPI_SYS_INT_T0_SET        0x00000000
+#define ESPI_SYS_INT_T1_SET        0x00000000
+#define ESPI_SYS_INT_T2_SET \
+(ESPI_SYSEVT_HOST_RST_WARN | ESPI_SYSEVT_OOB_RST_WARN | ESPI_SYSEVT_PLT_RST_N)
+#define ESPI_SYS_INT_SET \
+(ESPI_SYSEVT_HOST_RST_WARN | ESPI_SYSEVT_OOB_RST_WARN | ESPI_SYSEVT_PLT_RST_N)
+
+/* Setup Interrupt Type/Enable of System Event 1 from Master
+ *				   T2 T1 T0
+ *  1). SUS_WARN    : Rising Edge   0  0  1
+ */
+#define ESPI_SYS1_INT_T0_SET        ESPI_SYSEVT1_SUS_WARN
+#define ESPI_SYS1_INT_T1_SET        0x00000000
+#define ESPI_SYS1_INT_T2_SET        0x00000000
+#define ESPI_SYS1_INT_SET           ESPI_SYSEVT1_SUS_WARN
+
+static int aspeed_espi_slave_config_irq(struct aspeed_espi_slave_data *priv,
+			struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	int irq;
+	int rc;
+
+	irq = platform_get_irq(pdev, 0);
+	if (irq < 0)
+		return irq;
+
+	rc = devm_request_irq(dev, irq, aspeed_espi_slave_irq, IRQF_SHARED,
+			dev_name(dev), priv);
+	if (rc < 0)
+		return rc;
+
+	regmap_update_bits(priv->map, ESPI_CTRL, ESPI_CTRL_OOB_CHRDY,
+			ESPI_CTRL_OOB_CHRDY);
+
+	regmap_write(priv->map, ESPI_SYS_INT_T0, ESPI_SYS_INT_T0_SET);
+	regmap_write(priv->map, ESPI_SYS_INT_T1, ESPI_SYS_INT_T1_SET);
+	regmap_write(priv->map, ESPI_SYS_INT_T2, ESPI_SYS_INT_T2_SET);
+	regmap_write(priv->map, ESPI_SYS_IER, ESPI_SYS_INT_SET);
+
+	regmap_write(priv->map, ESPI_SYS1_INT_T0, ESPI_SYS1_INT_T0_SET);
+	regmap_write(priv->map, ESPI_SYS1_INT_T1, ESPI_SYS1_INT_T1_SET);
+	regmap_write(priv->map, ESPI_SYS1_INT_T2, ESPI_SYS1_INT_T2_SET);
+	regmap_write(priv->map, ESPI_SYS1_IER, ESPI_SYS1_INT_SET);
+
+	regmap_write(priv->map, ESPI_IER, 0xFFFFFFFF);
+
+	return 0;
+}
+
+static void aspeed_espi_slave_boot_ack(struct aspeed_espi_slave_data *priv)
+{
+	u32 evt;
+
+	if (regmap_read(priv->map, ESPI_SYS_EVENT, &evt) == 0 &&
+	    (evt & ESPI_SYSEVT_SLAVE_BOOT_STATUS) == 0)
+		regmap_write(priv->map, ESPI_SYS_EVENT, evt |
+			ESPI_SYSEVT_SLAVE_BOOT_STATUS |
+			ESPI_SYSEVT_SLAVE_BOOT_DONE);
+
+	if (regmap_read(priv->map, ESPI_SYS1_EVENT, &evt) == 0 &&
+	    (evt & ESPI_SYSEVT1_SUS_WARN) != 0)
+		regmap_write(priv->map, ESPI_SYS1_EVENT, evt |
+			ESPI_SYSEVT1_SUS_ACK);
+}
+
+static const struct regmap_config espi_slave_regmap_cfg = {
+	.reg_bits = 32,
+	.reg_stride = 4,
+	.val_bits = 32,
+	.max_register = ESPI_SYS1_ISR,
+};
+
+static int aspeed_espi_slave_probe(struct platform_device *pdev)
+{
+	struct aspeed_espi_slave_data *priv;
+	struct device *dev = &pdev->dev;
+	struct resource *res;
+	void __iomem *regs;
+	int rc;
+
+	dev_set_name(dev, DEVICE_NAME);
+
+	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	regs = devm_ioremap_resource(dev, res);
+	if (IS_ERR(regs))
+		return PTR_ERR(regs);
+
+	priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
+	if (!priv)
+		return -ENOMEM;
+
+	priv->map = devm_regmap_init_mmio(dev, regs, &espi_slave_regmap_cfg);
+	if (IS_ERR(priv->map))
+		return PTR_ERR(priv->map);
+
+	rc = aspeed_espi_slave_config_irq(priv, pdev);
+	if (rc)
+		return rc;
+
+	aspeed_espi_slave_boot_ack(priv);
+
+	platform_set_drvdata(pdev, priv);
+
+	return 0;
+}
+
+static const struct of_device_id of_espi_slave_match_table[] = {
+	{ .compatible = "aspeed,ast2500-espi-slave" },
+	{ }
+};
+
+static struct platform_driver aspeed_espi_slave_driver = {
+	.driver = {
+		.name           = DEVICE_NAME,
+		.of_match_table = of_espi_slave_match_table,
+	},
+	.probe = aspeed_espi_slave_probe,
+};
+
+module_platform_driver(aspeed_espi_slave_driver);
+
+MODULE_DEVICE_TABLE(of, of_espi_slave_match_table);
+MODULE_LICENSE("GPL v2");
+MODULE_AUTHOR("Haiyue Wang <haiyue.wang@linux.intel.com>");
+MODULE_DESCRIPTION("Linux device interface to the eSPI slave");
-- 
2.7.4