bus: mhi: ep: Add support for registering MHI endpoint controllers

This commit adds support for registering MHI endpoint controller drivers
with the MHI endpoint stack. MHI endpoint controller drivers manage
the interaction with the host machines (such as x86). They are also the
MHI endpoint bus master in charge of managing the physical link between
the host and endpoint device. Eventhough the MHI spec is bus agnostic,
the current implementation is entirely based on PCIe bus.

The endpoint controller driver encloses all information about the
underlying physical bus like PCIe. The registration process involves
parsing the channel configuration and allocating an MHI EP device.

Channels used in the endpoint stack follows the perspective of the MHI
host stack. i.e.,

UL - From host to endpoint
DL - From endpoint to host

Reviewed-by: Alex Elder <elder@linaro.org>
Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Link: https://lore.kernel.org/r/20220405135754.6622-2-manivannan.sadhasivam@linaro.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

6 files changed, 408 insertions, 0 deletions

diff --git a/drivers/bus/mhi/Kconfig b/drivers/bus/mhi/Kconfig
index 4748df7f9cd5..b39a11e6c624 100644
--- a/drivers/bus/mhi/Kconfig
+++ b/drivers/bus/mhi/Kconfig
@@ -6,3 +6,4 @@
 #
 
 source "drivers/bus/mhi/host/Kconfig"
+source "drivers/bus/mhi/ep/Kconfig"
diff --git a/drivers/bus/mhi/Makefile b/drivers/bus/mhi/Makefile
index 5f5708a249f5..46981331b38f 100644
--- a/drivers/bus/mhi/Makefile
+++ b/drivers/bus/mhi/Makefile
@@ -1,2 +1,5 @@
 # Host MHI stack
 obj-y += host/
+
+# Endpoint MHI stack
+obj-y += ep/
diff --git a/drivers/bus/mhi/ep/Kconfig b/drivers/bus/mhi/ep/Kconfig
new file mode 100644
index 000000000000..90ab3b040672
--- /dev/null
+++ b/drivers/bus/mhi/ep/Kconfig
@@ -0,0 +1,10 @@
+config MHI_BUS_EP
+	tristate "Modem Host Interface (MHI) bus Endpoint implementation"
+	help
+	  Bus driver for MHI protocol. Modem Host Interface (MHI) is a
+	  communication protocol used by a host processor to control
+	  and communicate a modem device over a high speed peripheral
+	  bus or shared memory.
+
+	  MHI_BUS_EP implements the MHI protocol for the endpoint devices,
+	  such as SDX55 modem connected to the host machine over PCIe.
diff --git a/drivers/bus/mhi/ep/Makefile b/drivers/bus/mhi/ep/Makefile
new file mode 100644
index 000000000000..64e29252b608
--- /dev/null
+++ b/drivers/bus/mhi/ep/Makefile
@@ -0,0 +1,2 @@
+obj-$(CONFIG_MHI_BUS_EP) += mhi_ep.o
+mhi_ep-y := main.o
diff --git a/drivers/bus/mhi/ep/internal.h b/drivers/bus/mhi/ep/internal.h
new file mode 100644
index 000000000000..0d3923186a5e
--- /dev/null
+++ b/drivers/bus/mhi/ep/internal.h
@@ -0,0 +1,156 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (c) 2022, Linaro Ltd.
+ *
+ */
+
+#ifndef _MHI_EP_INTERNAL_
+#define _MHI_EP_INTERNAL_
+
+#include <linux/bitfield.h>
+
+#include "../common.h"
+
+extern struct bus_type mhi_ep_bus_type;
+
+#define MHI_REG_OFFSET				0x100
+#define BHI_REG_OFFSET				0x200
+
+/* MHI registers */
+#define EP_MHIREGLEN				(MHI_REG_OFFSET + MHIREGLEN)
+#define EP_MHIVER				(MHI_REG_OFFSET + MHIVER)
+#define EP_MHICFG				(MHI_REG_OFFSET + MHICFG)
+#define EP_CHDBOFF				(MHI_REG_OFFSET + CHDBOFF)
+#define EP_ERDBOFF				(MHI_REG_OFFSET + ERDBOFF)
+#define EP_BHIOFF				(MHI_REG_OFFSET + BHIOFF)
+#define EP_BHIEOFF				(MHI_REG_OFFSET + BHIEOFF)
+#define EP_DEBUGOFF				(MHI_REG_OFFSET + DEBUGOFF)
+#define EP_MHICTRL				(MHI_REG_OFFSET + MHICTRL)
+#define EP_MHISTATUS				(MHI_REG_OFFSET + MHISTATUS)
+#define EP_CCABAP_LOWER				(MHI_REG_OFFSET + CCABAP_LOWER)
+#define EP_CCABAP_HIGHER			(MHI_REG_OFFSET + CCABAP_HIGHER)
+#define EP_ECABAP_LOWER				(MHI_REG_OFFSET + ECABAP_LOWER)
+#define EP_ECABAP_HIGHER			(MHI_REG_OFFSET + ECABAP_HIGHER)
+#define EP_CRCBAP_LOWER				(MHI_REG_OFFSET + CRCBAP_LOWER)
+#define EP_CRCBAP_HIGHER			(MHI_REG_OFFSET + CRCBAP_HIGHER)
+#define EP_CRDB_LOWER				(MHI_REG_OFFSET + CRDB_LOWER)
+#define EP_CRDB_HIGHER				(MHI_REG_OFFSET + CRDB_HIGHER)
+#define EP_MHICTRLBASE_LOWER			(MHI_REG_OFFSET + MHICTRLBASE_LOWER)
+#define EP_MHICTRLBASE_HIGHER			(MHI_REG_OFFSET + MHICTRLBASE_HIGHER)
+#define EP_MHICTRLLIMIT_LOWER			(MHI_REG_OFFSET + MHICTRLLIMIT_LOWER)
+#define EP_MHICTRLLIMIT_HIGHER			(MHI_REG_OFFSET + MHICTRLLIMIT_HIGHER)
+#define EP_MHIDATABASE_LOWER			(MHI_REG_OFFSET + MHIDATABASE_LOWER)
+#define EP_MHIDATABASE_HIGHER			(MHI_REG_OFFSET + MHIDATABASE_HIGHER)
+#define EP_MHIDATALIMIT_LOWER			(MHI_REG_OFFSET + MHIDATALIMIT_LOWER)
+#define EP_MHIDATALIMIT_HIGHER			(MHI_REG_OFFSET + MHIDATALIMIT_HIGHER)
+
+/* MHI BHI registers */
+#define EP_BHI_INTVEC				(BHI_REG_OFFSET + BHI_INTVEC)
+#define EP_BHI_EXECENV				(BHI_REG_OFFSET + BHI_EXECENV)
+
+/* MHI Doorbell registers */
+#define CHDB_LOWER_n(n)				(0x400 + 0x8 * (n))
+#define CHDB_HIGHER_n(n)			(0x404 + 0x8 * (n))
+#define ERDB_LOWER_n(n)				(0x800 + 0x8 * (n))
+#define ERDB_HIGHER_n(n)			(0x804 + 0x8 * (n))
+
+#define MHI_CTRL_INT_STATUS			0x4
+#define MHI_CTRL_INT_STATUS_MSK			BIT(0)
+#define MHI_CTRL_INT_STATUS_CRDB_MSK		BIT(1)
+#define MHI_CHDB_INT_STATUS_n(n)		(0x28 + 0x4 * (n))
+#define MHI_ERDB_INT_STATUS_n(n)		(0x38 + 0x4 * (n))
+
+#define MHI_CTRL_INT_CLEAR			0x4c
+#define MHI_CTRL_INT_MMIO_WR_CLEAR		BIT(2)
+#define MHI_CTRL_INT_CRDB_CLEAR			BIT(1)
+#define MHI_CTRL_INT_CRDB_MHICTRL_CLEAR		BIT(0)
+
+#define MHI_CHDB_INT_CLEAR_n(n)			(0x70 + 0x4 * (n))
+#define MHI_CHDB_INT_CLEAR_n_CLEAR_ALL		GENMASK(31, 0)
+#define MHI_ERDB_INT_CLEAR_n(n)			(0x80 + 0x4 * (n))
+#define MHI_ERDB_INT_CLEAR_n_CLEAR_ALL		GENMASK(31, 0)
+
+/*
+ * Unlike the usual "masking" convention, writing "1" to a bit in this register
+ * enables the interrupt and writing "0" will disable it..
+ */
+#define MHI_CTRL_INT_MASK			0x94
+#define MHI_CTRL_INT_MASK_MASK			GENMASK(1, 0)
+#define MHI_CTRL_MHICTRL_MASK			BIT(0)
+#define MHI_CTRL_CRDB_MASK			BIT(1)
+
+#define MHI_CHDB_INT_MASK_n(n)			(0xb8 + 0x4 * (n))
+#define MHI_CHDB_INT_MASK_n_EN_ALL		GENMASK(31, 0)
+#define MHI_ERDB_INT_MASK_n(n)			(0xc8 + 0x4 * (n))
+#define MHI_ERDB_INT_MASK_n_EN_ALL		GENMASK(31, 0)
+
+#define NR_OF_CMD_RINGS				1
+#define MHI_MASK_ROWS_CH_DB			4
+#define MHI_MASK_ROWS_EV_DB			4
+#define MHI_MASK_CH_LEN				32
+#define MHI_MASK_EV_LEN				32
+
+/* Generic context */
+struct mhi_generic_ctx {
+	__le32 reserved0;
+	__le32 reserved1;
+	__le32 reserved2;
+
+	__le64 rbase __packed __aligned(4);
+	__le64 rlen __packed __aligned(4);
+	__le64 rp __packed __aligned(4);
+	__le64 wp __packed __aligned(4);
+};
+
+enum mhi_ep_ring_type {
+	RING_TYPE_CMD,
+	RING_TYPE_ER,
+	RING_TYPE_CH,
+};
+
+/* Ring element */
+union mhi_ep_ring_ctx {
+	struct mhi_cmd_ctxt cmd;
+	struct mhi_event_ctxt ev;
+	struct mhi_chan_ctxt ch;
+	struct mhi_generic_ctx generic;
+};
+
+struct mhi_ep_ring {
+	struct mhi_ep_cntrl *mhi_cntrl;
+	union mhi_ep_ring_ctx *ring_ctx;
+	struct mhi_ring_element *ring_cache;
+	enum mhi_ep_ring_type type;
+	u64 rbase;
+	size_t rd_offset;
+	size_t wr_offset;
+	size_t ring_size;
+	u32 db_offset_h;
+	u32 db_offset_l;
+	u32 ch_id;
+};
+
+struct mhi_ep_cmd {
+	struct mhi_ep_ring ring;
+};
+
+struct mhi_ep_event {
+	struct mhi_ep_ring ring;
+};
+
+struct mhi_ep_chan {
+	char *name;
+	struct mhi_ep_device *mhi_dev;
+	struct mhi_ep_ring ring;
+	struct mutex lock;
+	void (*xfer_cb)(struct mhi_ep_device *mhi_dev, struct mhi_result *result);
+	enum mhi_ch_state state;
+	enum dma_data_direction dir;
+	u64 tre_loc;
+	u32 tre_size;
+	u32 tre_bytes_left;
+	u32 chan;
+	bool skip_td;
+};
+
+#endif
diff --git a/drivers/bus/mhi/ep/main.c b/drivers/bus/mhi/ep/main.c
new file mode 100644
index 000000000000..d932ad01761b
--- /dev/null
+++ b/drivers/bus/mhi/ep/main.c
@@ -0,0 +1,236 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * MHI Endpoint bus stack
+ *
+ * Copyright (C) 2022 Linaro Ltd.
+ * Author: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
+ */
+
+#include <linux/bitfield.h>
+#include <linux/delay.h>
+#include <linux/dma-direction.h>
+#include <linux/interrupt.h>
+#include <linux/io.h>
+#include <linux/mhi_ep.h>
+#include <linux/mod_devicetable.h>
+#include <linux/module.h>
+#include "internal.h"
+
+static DEFINE_IDA(mhi_ep_cntrl_ida);
+
+static void mhi_ep_release_device(struct device *dev)
+{
+	struct mhi_ep_device *mhi_dev = to_mhi_ep_device(dev);
+
+	if (mhi_dev->dev_type == MHI_DEVICE_CONTROLLER)
+		mhi_dev->mhi_cntrl->mhi_dev = NULL;
+
+	/*
+	 * We need to set the mhi_chan->mhi_dev to NULL here since the MHI
+	 * devices for the channels will only get created in mhi_ep_create_device()
+	 * if the mhi_dev associated with it is NULL.
+	 */
+	if (mhi_dev->ul_chan)
+		mhi_dev->ul_chan->mhi_dev = NULL;
+
+	if (mhi_dev->dl_chan)
+		mhi_dev->dl_chan->mhi_dev = NULL;
+
+	kfree(mhi_dev);
+}
+
+static struct mhi_ep_device *mhi_ep_alloc_device(struct mhi_ep_cntrl *mhi_cntrl,
+						 enum mhi_device_type dev_type)
+{
+	struct mhi_ep_device *mhi_dev;
+	struct device *dev;
+
+	mhi_dev = kzalloc(sizeof(*mhi_dev), GFP_KERNEL);
+	if (!mhi_dev)
+		return ERR_PTR(-ENOMEM);
+
+	dev = &mhi_dev->dev;
+	device_initialize(dev);
+	dev->bus = &mhi_ep_bus_type;
+	dev->release = mhi_ep_release_device;
+
+	/* Controller device is always allocated first */
+	if (dev_type == MHI_DEVICE_CONTROLLER)
+		/* for MHI controller device, parent is the bus device (e.g. PCI EPF) */
+		dev->parent = mhi_cntrl->cntrl_dev;
+	else
+		/* for MHI client devices, parent is the MHI controller device */
+		dev->parent = &mhi_cntrl->mhi_dev->dev;
+
+	mhi_dev->mhi_cntrl = mhi_cntrl;
+	mhi_dev->dev_type = dev_type;
+
+	return mhi_dev;
+}
+
+static int mhi_ep_chan_init(struct mhi_ep_cntrl *mhi_cntrl,
+			    const struct mhi_ep_cntrl_config *config)
+{
+	const struct mhi_ep_channel_config *ch_cfg;
+	struct device *dev = mhi_cntrl->cntrl_dev;
+	u32 chan, i;
+	int ret = -EINVAL;
+
+	mhi_cntrl->max_chan = config->max_channels;
+
+	/*
+	 * Allocate max_channels supported by the MHI endpoint and populate
+	 * only the defined channels
+	 */
+	mhi_cntrl->mhi_chan = kcalloc(mhi_cntrl->max_chan, sizeof(*mhi_cntrl->mhi_chan),
+				      GFP_KERNEL);
+	if (!mhi_cntrl->mhi_chan)
+		return -ENOMEM;
+
+	for (i = 0; i < config->num_channels; i++) {
+		struct mhi_ep_chan *mhi_chan;
+
+		ch_cfg = &config->ch_cfg[i];
+
+		chan = ch_cfg->num;
+		if (chan >= mhi_cntrl->max_chan) {
+			dev_err(dev, "Channel (%u) exceeds maximum available channels (%u)\n",
+				chan, mhi_cntrl->max_chan);
+			goto error_chan_cfg;
+		}
+
+		/* Bi-directional and direction less channels are not supported */
+		if (ch_cfg->dir == DMA_BIDIRECTIONAL || ch_cfg->dir == DMA_NONE) {
+			dev_err(dev, "Invalid direction (%u) for channel (%u)\n",
+				ch_cfg->dir, chan);
+			goto error_chan_cfg;
+		}
+
+		mhi_chan = &mhi_cntrl->mhi_chan[chan];
+		mhi_chan->name = ch_cfg->name;
+		mhi_chan->chan = chan;
+		mhi_chan->dir = ch_cfg->dir;
+		mutex_init(&mhi_chan->lock);
+	}
+
+	return 0;
+
+error_chan_cfg:
+	kfree(mhi_cntrl->mhi_chan);
+
+	return ret;
+}
+
+/*
+ * Allocate channel and command rings here. Event rings will be allocated
+ * in mhi_ep_power_up() as the config comes from the host.
+ */
+int mhi_ep_register_controller(struct mhi_ep_cntrl *mhi_cntrl,
+				const struct mhi_ep_cntrl_config *config)
+{
+	struct mhi_ep_device *mhi_dev;
+	int ret;
+
+	if (!mhi_cntrl || !mhi_cntrl->cntrl_dev)
+		return -EINVAL;
+
+	ret = mhi_ep_chan_init(mhi_cntrl, config);
+	if (ret)
+		return ret;
+
+	mhi_cntrl->mhi_cmd = kcalloc(NR_OF_CMD_RINGS, sizeof(*mhi_cntrl->mhi_cmd), GFP_KERNEL);
+	if (!mhi_cntrl->mhi_cmd) {
+		ret = -ENOMEM;
+		goto err_free_ch;
+	}
+
+	/* Set controller index */
+	ret = ida_alloc(&mhi_ep_cntrl_ida, GFP_KERNEL);
+	if (ret < 0)
+		goto err_free_cmd;
+
+	mhi_cntrl->index = ret;
+
+	/* Allocate the controller device */
+	mhi_dev = mhi_ep_alloc_device(mhi_cntrl, MHI_DEVICE_CONTROLLER);
+	if (IS_ERR(mhi_dev)) {
+		dev_err(mhi_cntrl->cntrl_dev, "Failed to allocate controller device\n");
+		ret = PTR_ERR(mhi_dev);
+		goto err_ida_free;
+	}
+
+	dev_set_name(&mhi_dev->dev, "mhi_ep%u", mhi_cntrl->index);
+	mhi_dev->name = dev_name(&mhi_dev->dev);
+	mhi_cntrl->mhi_dev = mhi_dev;
+
+	ret = device_add(&mhi_dev->dev);
+	if (ret)
+		goto err_put_dev;
+
+	dev_dbg(&mhi_dev->dev, "MHI EP Controller registered\n");
+
+	return 0;
+
+err_put_dev:
+	put_device(&mhi_dev->dev);
+err_ida_free:
+	ida_free(&mhi_ep_cntrl_ida, mhi_cntrl->index);
+err_free_cmd:
+	kfree(mhi_cntrl->mhi_cmd);
+err_free_ch:
+	kfree(mhi_cntrl->mhi_chan);
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(mhi_ep_register_controller);
+
+void mhi_ep_unregister_controller(struct mhi_ep_cntrl *mhi_cntrl)
+{
+	struct mhi_ep_device *mhi_dev = mhi_cntrl->mhi_dev;
+
+	kfree(mhi_cntrl->mhi_cmd);
+	kfree(mhi_cntrl->mhi_chan);
+
+	device_del(&mhi_dev->dev);
+	put_device(&mhi_dev->dev);
+
+	ida_free(&mhi_ep_cntrl_ida, mhi_cntrl->index);
+}
+EXPORT_SYMBOL_GPL(mhi_ep_unregister_controller);
+
+static int mhi_ep_match(struct device *dev, struct device_driver *drv)
+{
+	struct mhi_ep_device *mhi_dev = to_mhi_ep_device(dev);
+
+	/*
+	 * If the device is a controller type then there is no client driver
+	 * associated with it
+	 */
+	if (mhi_dev->dev_type == MHI_DEVICE_CONTROLLER)
+		return 0;
+
+	return 0;
+};
+
+struct bus_type mhi_ep_bus_type = {
+	.name = "mhi_ep",
+	.dev_name = "mhi_ep",
+	.match = mhi_ep_match,
+};
+
+static int __init mhi_ep_init(void)
+{
+	return bus_register(&mhi_ep_bus_type);
+}
+
+static void __exit mhi_ep_exit(void)
+{
+	bus_unregister(&mhi_ep_bus_type);
+}
+
+postcore_initcall(mhi_ep_init);
+module_exit(mhi_ep_exit);
+
+MODULE_LICENSE("GPL v2");
+MODULE_DESCRIPTION("MHI Bus Endpoint stack");
+MODULE_AUTHOR("Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>");