[PATCH v2 07/17] soc: qcom: ipa: the generic software interface

[Alex Elder <elder@linaro.org>]

This patch includes "gsi.c", which implements the generic software
interface (GSI) for IPA.  The generic software interface abstracts
channels, which provide a means of transferring data either from the
AP to the IPA, or from the IPA to the AP.  A ring buffer of "transfer
elements" (TREs) is used to describe data transfers to perform.  The
AP writes a doorbell register associated with a channel to let it know
it has added new entries (for an AP->IPA channel) or has finished
processing entries (for an IPA->AP channel).

Each channel also has an event ring buffer, used by the IPA to
communicate information about events related to a channel (for
example, the completion of TREs).  The IPA writes its own doorbell
register, which triggers an interrupt on the AP, to signal that
new event information has arrived.

Signed-off-by: Alex Elder <elder@linaro.org>
---
 drivers/net/ipa/gsi.c | 1635 +++++++++++++++++++++++++++++++++++++++++
 1 file changed, 1635 insertions(+)
 create mode 100644 drivers/net/ipa/gsi.c

diff --git a/drivers/net/ipa/gsi.c b/drivers/net/ipa/gsi.c
new file mode 100644
index 000000000000..a749d3b0d792
--- /dev/null
+++ b/drivers/net/ipa/gsi.c
@@ -0,0 +1,1635 @@
+// SPDX-License-Identifier: GPL-2.0
+
+/* Copyright (c) 2015-2018, The Linux Foundation. All rights reserved.
+ * Copyright (C) 2018-2019 Linaro Ltd.
+ */
+
+#include <linux/types.h>
+#include <linux/bits.h>
+#include <linux/bitfield.h>
+#include <linux/mutex.h>
+#include <linux/completion.h>
+#include <linux/io.h>
+#include <linux/bug.h>
+#include <linux/interrupt.h>
+#include <linux/platform_device.h>
+#include <linux/netdevice.h>
+
+#include "gsi.h"
+#include "gsi_reg.h"
+#include "gsi_private.h"
+#include "gsi_trans.h"
+#include "ipa_gsi.h"
+#include "ipa_data.h"
+
+/**
+ * DOC: The IPA Generic Software Interface
+ *
+ * The generic software interface (GSI) is an integral component of the IPA,
+ * providing a well-defined communication layer between the AP subsystem
+ * and the IPA core.  The modem uses the GSI layer as well.
+ *
+ *	--------	     ---------
+ *	|      |	     |	     |
+ *	|  AP  +<---.	.----+ Modem |
+ *	|      +--. |	| .->+	     |
+ *	|      |  | |	| |  |	     |
+ *	--------  | |	| |  ---------
+ *		  v |	v |
+ *		--+-+---+-+--
+ *		|    GSI    |
+ *		|-----------|
+ *		|	    |
+ *		|    IPA    |
+ *		|	    |
+ *		-------------
+ *
+ * In the above diagram, the AP and Modem represent "execution environments"
+ * (EEs), which are independent operating environments that use the IPA for
+ * data transfer.
+ *
+ * Each EE uses a set of unidirectional GSI "channels," which allow transfer
+ * of data to or from the IPA.  A channel is implemented as a ring buffer,
+ * with a DRAM-resident array of "transfer elements" (TREs) available to
+ * describe transfers to or from other EEs through the IPA.  A transfer
+ * element can also contain an immediate command, requesting the IPA perform
+ * actions other than data transfer.
+ *
+ * Each TRE refers to a block of data--also located DRAM.  After writing one
+ * or more TREs to a channel, the writer (either the IPA or an EE) writes a
+ * doorbell register to inform the receiving side how many elements have
+ * been written.  Writing to a doorbell register triggers within the GSI.
+ *
+ * Each channel has a GSI "event ring" associated with it.  An event ring
+ * is implemented very much like a channel ring, but is always directed from
+ * the IPA to an EE.  The IPA notifies an EE (such as the AP) about channel
+ * events by adding an entry to the event ring associated with the channel.
+ * The GSI then writes its doorbell for the event ring, causing the target
+ * EE to be interrupted.  Each entry in an event ring contains a pointer
+ * to the channel TRE whose completion the event represents.
+ *
+ * Each TRE in a channel ring has a set of flags.  One flag indicates whether
+ * the completion of the transfer operation generates an entry (and possibly
+ * an interrupt) in the channel's event ring.  Other flags allow transfer
+ * elements to be chained together, forming a single logical transaction.
+ * TRE flags are used to control whether and when interrupts are generated
+ * to signal completion of channel transfers.
+ *
+ * Elements in channel and event rings are completed (or consumed) strictly
+ * in order.  Completion of one entry implies the completion of all preceding
+ * entries.  A single completion interrupt can therefore communicate the
+ * completion of many transfers.
+ *
+ * Note that all GSI registers are little-endian, which is the assumed
+ * endianness of I/O space accesses.  The accessor functions perform byte
+ * swapping if needed (i.e., for a big endian CPU).
+ */
+
+/* Delay period for interrupt moderation (in 32KHz IPA internal timer ticks) */
+#define IPA_GSI_EVT_RING_INT_MODT	(32 * 1) /* 1ms under 32KHz clock */
+
+#define GSI_CMD_TIMEOUT		5	/* seconds */
+
+#define GSI_MHI_ER_START	10	/* First reserved event number */
+#define GSI_MHI_ER_END		16	/* Last reserved event number */
+
+#define GSI_ISR_MAX_ITER	50	/* Detect interrupt storms */
+
+/* Hardware values from the error log register error code field */
+enum gsi_err_code {
+	GSI_INVALID_TRE_ERR			= 0x1,
+	GSI_OUT_OF_BUFFERS_ERR			= 0x2,
+	GSI_OUT_OF_RESOURCES_ERR		= 0x3,
+	GSI_UNSUPPORTED_INTER_EE_OP_ERR		= 0x4,
+	GSI_EVT_RING_EMPTY_ERR			= 0x5,
+	GSI_NON_ALLOCATED_EVT_ACCESS_ERR	= 0x6,
+	GSI_HWO_1_ERR				= 0x8,
+};
+
+/* Hardware values from the error log register error type field */
+enum gsi_err_type {
+	GSI_ERR_TYPE_GLOB	= 0x1,
+	GSI_ERR_TYPE_CHAN	= 0x2,
+	GSI_ERR_TYPE_EVT	= 0x3,
+};
+
+/* Fields in an error log register at GSI_ERROR_LOG_OFFSET */
+#define GSI_LOG_ERR_ARG3_FMASK		GENMASK(3, 0)
+#define GSI_LOG_ERR_ARG2_FMASK		GENMASK(7, 4)
+#define GSI_LOG_ERR_ARG1_FMASK		GENMASK(11, 8)
+#define GSI_LOG_ERR_CODE_FMASK		GENMASK(15, 12)
+#define GSI_LOG_ERR_VIRT_IDX_FMASK	GENMASK(23, 19)
+#define GSI_LOG_ERR_TYPE_FMASK		GENMASK(27, 24)
+#define GSI_LOG_ERR_EE_FMASK		GENMASK(31, 28)
+
+/* Hardware values used when programming an event ring */
+enum gsi_evt_chtype {
+	GSI_EVT_CHTYPE_MHI_EV	= 0x0,
+	GSI_EVT_CHTYPE_XHCI_EV	= 0x1,
+	GSI_EVT_CHTYPE_GPI_EV	= 0x2,
+	GSI_EVT_CHTYPE_XDCI_EV	= 0x3,
+};
+
+/* Hardware values used when programming a channel */
+enum gsi_channel_protocol {
+	GSI_CHANNEL_PROTOCOL_MHI	= 0x0,
+	GSI_CHANNEL_PROTOCOL_XHCI	= 0x1,
+	GSI_CHANNEL_PROTOCOL_GPI	= 0x2,
+	GSI_CHANNEL_PROTOCOL_XDCI	= 0x3,
+};
+
+/* Hardware values representing an event ring immediate command opcode */
+enum gsi_evt_ch_cmd_opcode {
+	GSI_EVT_ALLOCATE	= 0x0,
+	GSI_EVT_RESET		= 0x9,
+	GSI_EVT_DE_ALLOC	= 0xa,
+};
+
+/* Hardware values representing a channel immediate command opcode */
+enum gsi_ch_cmd_opcode {
+	GSI_CH_ALLOCATE	= 0x0,
+	GSI_CH_START	= 0x1,
+	GSI_CH_STOP	= 0x2,
+	GSI_CH_RESET	= 0x9,
+	GSI_CH_DE_ALLOC	= 0xa,
+	GSI_CH_DB_STOP	= 0xb,
+};
+
+/** gsi_gpi_channel_scratch - GPI protocol scratch register
+ *
+ * @max_outstanding_tre:
+ *	Defines the maximum number of TREs allowed in a single transaction
+ *	on a channel (in Bytes).  This determines the amount of prefetch
+ *	performed by the hardware.  We configure this to equal the size of
+ *	the TLV FIFO for the channel.
+ * @outstanding_threshold:
+ *	Defines the threshold (in Bytes) determining when the sequencer
+ *	should update the channel doorbell.  We configure this to equal
+ *	the size of two TREs.
+ */
+struct gsi_gpi_channel_scratch {
+	u64 reserved1;
+	u16 reserved2;
+	u16 max_outstanding_tre;
+	u16 reserved3;
+	u16 outstanding_threshold;
+};
+
+/** gsi_channel_scratch - channel scratch configuration area
+ *
+ * The exact interpretation of this register is protocol-specific.
+ * We only use GPI channels; see struct gsi_gpi_channel_scratch, above.
+ */
+union gsi_channel_scratch {
+	struct gsi_gpi_channel_scratch gpi;
+	struct {
+		u32 word1;
+		u32 word2;
+		u32 word3;
+		u32 word4;
+	} data;
+};
+
+/* Return the channel id associated with a given channel */
+static u32 gsi_channel_id(struct gsi_channel *channel)
+{
+	return channel - &channel->gsi->channel[0];
+}
+
+/* Report the number of bytes queued to hardware since last call */
+void gsi_channel_tx_queued(struct gsi_channel *channel)
+{
+	u32 trans_count;
+	u32 byte_count;
+
+	trans_count = channel->trans_count - channel->queued_trans_count;
+	byte_count = channel->byte_count - channel->queued_byte_count;
+	channel->queued_trans_count = channel->trans_count;
+	channel->queued_byte_count = channel->byte_count;
+
+	ipa_gsi_channel_tx_queued(channel->gsi, gsi_channel_id(channel),
+				  trans_count, byte_count);
+}
+
+static void gsi_irq_event_enable(struct gsi *gsi, u32 evt_ring_id)
+{
+	u32 val;
+
+	gsi->event_enable_bitmap |= BIT(evt_ring_id);
+	val = gsi->event_enable_bitmap;
+	iowrite32(val, gsi->virt + GSI_CNTXT_SRC_IEOB_IRQ_MSK_OFFSET);
+}
+
+static void gsi_irq_event_disable(struct gsi *gsi, u32 evt_ring_id)
+{
+	u32 val;
+
+	gsi->event_enable_bitmap &= ~BIT(evt_ring_id);
+	val = gsi->event_enable_bitmap;
+	iowrite32(val, gsi->virt + GSI_CNTXT_SRC_IEOB_IRQ_MSK_OFFSET);
+}
+
+/* Enable all GSI_interrupt types */
+static void gsi_irq_enable(struct gsi *gsi)
+{
+	u32 val;
+
+	/* Inter EE commands / interrupt are not supported. */
+	val = GSI_CNTXT_TYPE_IRQ_MSK_ALL;
+	iowrite32(val, gsi->virt + GSI_CNTXT_TYPE_IRQ_MSK_OFFSET);
+
+	val = GENMASK(GSI_CHANNEL_MAX - 1, 0);
+	iowrite32(val, gsi->virt + GSI_CNTXT_SRC_CH_IRQ_MSK_OFFSET);
+
+	val = GENMASK(GSI_EVT_RING_MAX - 1, 0);
+	iowrite32(val, gsi->virt + GSI_CNTXT_SRC_EV_CH_IRQ_MSK_OFFSET);
+
+	/* Each IEOB interrupt is enabled (later) as needed by channels */
+	iowrite32(0, gsi->virt + GSI_CNTXT_SRC_IEOB_IRQ_MSK_OFFSET);
+
+	val = GSI_CNTXT_GLOB_IRQ_ALL;
+	iowrite32(val, gsi->virt + GSI_CNTXT_GLOB_IRQ_EN_OFFSET);
+
+	/* Never enable GSI_BREAK_POINT */
+	val = GSI_CNTXT_GSI_IRQ_ALL & ~EN_BREAK_POINT_FMASK;
+	iowrite32(val, gsi->virt + GSI_CNTXT_GSI_IRQ_EN_OFFSET);
+}
+
+/* Disable all GSI_interrupt types */
+static void gsi_irq_disable(struct gsi *gsi)
+{
+	iowrite32(0, gsi->virt + GSI_CNTXT_GSI_IRQ_EN_OFFSET);
+	iowrite32(0, gsi->virt + GSI_CNTXT_GLOB_IRQ_EN_OFFSET);
+	iowrite32(0, gsi->virt + GSI_CNTXT_SRC_IEOB_IRQ_MSK_OFFSET);
+	iowrite32(0, gsi->virt + GSI_CNTXT_SRC_EV_CH_IRQ_MSK_OFFSET);
+	iowrite32(0, gsi->virt + GSI_CNTXT_SRC_CH_IRQ_MSK_OFFSET);
+	iowrite32(0, gsi->virt + GSI_CNTXT_TYPE_IRQ_MSK_OFFSET);
+}
+
+/* Return the hardware's notion of the current state of a channel */
+static enum gsi_channel_state gsi_channel_state(struct gsi_channel *channel)
+{
+	u32 channel_id = gsi_channel_id(channel);
+	struct gsi *gsi = channel->gsi;
+	u32 val;
+
+	val = ioread32(gsi->virt + GSI_CH_C_CNTXT_0_OFFSET(channel_id));
+
+	return u32_get_bits(val, CHSTATE_FMASK);
+}
+
+/* Return the hardware's notion of the current state of an event ring */
+static enum gsi_evt_ring_state
+gsi_evt_ring_state(struct gsi *gsi, u32 evt_ring_id)
+{
+	u32 val = ioread32(gsi->virt + GSI_EV_CH_E_CNTXT_0_OFFSET(evt_ring_id));
+
+	return u32_get_bits(val, EV_CHSTATE_FMASK);
+}
+
+/* Channel control interrupt handler */
+static void gsi_isr_chan_ctrl(struct gsi *gsi)
+{
+	u32 channel_mask;
+
+	channel_mask = ioread32(gsi->virt + GSI_CNTXT_SRC_CH_IRQ_OFFSET);
+	iowrite32(channel_mask, gsi->virt + GSI_CNTXT_SRC_CH_IRQ_CLR_OFFSET);
+
+	while (channel_mask) {
+		u32 channel_id = __ffs(channel_mask);
+		struct gsi_channel *channel;
+
+		channel_mask ^= BIT(channel_id);
+
+		channel = &gsi->channel[channel_id];
+		channel->state = gsi_channel_state(channel);
+
+		complete(&channel->completion);
+	}
+}
+
+static void gsi_isr_evt_ctrl(struct gsi *gsi)
+{
+	u32 event_mask;
+
+	event_mask = ioread32(gsi->virt + GSI_CNTXT_SRC_EV_CH_IRQ_OFFSET);
+	iowrite32(event_mask, gsi->virt + GSI_CNTXT_SRC_EV_CH_IRQ_CLR_OFFSET);
+
+	while (event_mask) {
+		u32 evt_ring_id = __ffs(event_mask);
+		struct gsi_evt_ring *evt_ring;
+
+		event_mask ^= BIT(evt_ring_id);
+
+		evt_ring = &gsi->evt_ring[evt_ring_id];
+		evt_ring->state = gsi_evt_ring_state(gsi, evt_ring_id);
+
+		complete(&evt_ring->completion);
+	}
+}
+
+static void
+gsi_isr_glob_chan_err(struct gsi *gsi, u32 err_ee, u32 channel_id, u32 code)
+{
+	if (code == GSI_OUT_OF_RESOURCES_ERR) {
+		dev_err(gsi->dev, "channel %u out of resources\n", channel_id);
+		complete(&gsi->channel[channel_id].completion);
+		return;
+	}
+
+	/* Report, but otherwise ignore all other error codes */
+	dev_err(gsi->dev, "channel %u global error ee 0x%08x code 0x%08x\n",
+		channel_id, err_ee, code);
+}
+
+static void
+gsi_isr_glob_evt_err(struct gsi *gsi, u32 err_ee, u32 evt_ring_id, u32 code)
+{
+	if (code == GSI_OUT_OF_RESOURCES_ERR) {
+		struct gsi_evt_ring *evt_ring = &gsi->evt_ring[evt_ring_id];
+		u32 channel_id = gsi_channel_id(evt_ring->channel);
+
+		complete(&evt_ring->completion);
+		dev_err(gsi->dev, "evt_ring for channel %u out of resources\n",
+			channel_id);
+		return;
+	}
+
+	/* Report, but otherwise ignore all other error codes */
+	dev_err(gsi->dev, "event ring %u global error ee %u code 0x%08x\n",
+		evt_ring_id, err_ee, code);
+}
+
+static void gsi_isr_glob_err(struct gsi *gsi)
+{
+	enum gsi_err_type type;
+	enum gsi_err_code code;
+	u32 which;
+	u32 val;
+	u32 ee;
+
+	/* Get the logged error, then reinitialize the log */
+	val = ioread32(gsi->virt + GSI_ERROR_LOG_OFFSET);
+	iowrite32(0, gsi->virt + GSI_ERROR_LOG_OFFSET);
+	iowrite32(~0, gsi->virt + GSI_ERROR_LOG_CLR_OFFSET);
+
+	ee = u32_get_bits(val, GSI_LOG_ERR_EE_FMASK);
+	which = u32_get_bits(val, GSI_LOG_ERR_VIRT_IDX_FMASK);
+	type = u32_get_bits(val, GSI_LOG_ERR_TYPE_FMASK);
+	code = u32_get_bits(val, GSI_LOG_ERR_CODE_FMASK);
+
+	if (type == GSI_ERR_TYPE_CHAN)
+		gsi_isr_glob_chan_err(gsi, ee, which, code);
+	else if (type == GSI_ERR_TYPE_EVT)
+		gsi_isr_glob_evt_err(gsi, ee, which, code);
+	else	/* type GSI_ERR_TYPE_GLOB should be fatal */
+		dev_err(gsi->dev, "unexpected global error 0x%08x\n", type);
+}
+
+static void gsi_isr_glob_ee(struct gsi *gsi)
+{
+	u32 val;
+
+	val = ioread32(gsi->virt + GSI_CNTXT_GLOB_IRQ_STTS_OFFSET);
+
+	if (val & ERROR_INT_FMASK)
+		gsi_isr_glob_err(gsi);
+
+	iowrite32(val, gsi->virt + GSI_CNTXT_GLOB_IRQ_CLR_OFFSET);
+
+	val &= ~ERROR_INT_FMASK;
+
+	if (val & EN_GP_INT1_FMASK) {
+		dev_err(gsi->dev, "unexpected global INT1\n");
+		val ^= EN_GP_INT1_FMASK;
+	}
+
+	if (val)
+		dev_err(gsi->dev, "unexpected global interrupt 0x%08x\n", val);
+}
+
+/* I/O completion interrupt event */
+static void gsi_isr_ieob(struct gsi *gsi)
+{
+	u32 event_mask;
+
+	event_mask = ioread32(gsi->virt + GSI_CNTXT_SRC_IEOB_IRQ_OFFSET);
+	iowrite32(event_mask, gsi->virt + GSI_CNTXT_SRC_IEOB_IRQ_CLR_OFFSET);
+
+	while (event_mask) {
+		u32 evt_ring_id = __ffs(event_mask);
+
+		event_mask ^= BIT(evt_ring_id);
+
+		gsi_irq_event_disable(gsi, evt_ring_id);
+		napi_schedule(&gsi->evt_ring[evt_ring_id].channel->napi);
+	}
+}
+
+/* We don't currently expect to receive any inter-EE channel interrupts */
+static void gsi_isr_inter_ee_chan_ctrl(struct gsi *gsi)
+{
+	u32 channel_mask;
+
+	channel_mask = ioread32(gsi->virt + GSI_INTER_EE_SRC_CH_IRQ_OFFSET);
+	iowrite32(channel_mask, gsi->virt + GSI_INTER_EE_SRC_CH_IRQ_CLR_OFFSET);
+
+	while (channel_mask) {
+		u32 channel_id = __ffs(channel_mask);
+
+		dev_err(gsi->dev, "ch %u inter-EE interrupt\n", channel_id);
+		channel_mask ^= BIT(channel_id);
+	}
+}
+
+/* We don't currently expect to receive any inter-EE event interrupts */
+static void gsi_isr_inter_ee_evt_ctrl(struct gsi *gsi)
+{
+	u32 event_mask;
+
+	event_mask = ioread32(gsi->virt + GSI_INTER_EE_SRC_EV_CH_IRQ_OFFSET);
+	iowrite32(event_mask,
+		  gsi->virt + GSI_INTER_EE_SRC_EV_CH_IRQ_CLR_OFFSET);
+
+	while (event_mask) {
+		u32 evt_ring_id = __ffs(event_mask);
+
+		event_mask ^= BIT(evt_ring_id);
+
+		/* not currently expected */
+		dev_err(gsi->dev, "evt %u inter-EE interrupt\n", evt_ring_id);
+	}
+}
+
+/* We don't currently expect to receive any general event interrupts */
+static void gsi_isr_general(struct gsi *gsi)
+{
+	u32 val;
+
+	val = ioread32(gsi->virt + GSI_CNTXT_GSI_IRQ_STTS_OFFSET);
+	iowrite32(val, gsi->virt + GSI_CNTXT_GSI_IRQ_CLR_OFFSET);
+
+	if (val & CLR_BREAK_POINT_FMASK)
+		dev_err(gsi->dev, "breakpoint!\n");
+	val ^= CLR_BREAK_POINT_FMASK;
+
+	if (val)
+		dev_err(gsi->dev, "unexpected general interrupt 0x%08x\n", val);
+}
+
+/**
+ * gsi_isr() - Top level GSI interrupt service routine
+ * @irq:	Interrupt number (ignored)
+ * @dev_id:	GSI pointer supplied to request_irq()
+ *
+ * This is the main handler function registered for the GSI IRQ. Each type
+ * of interrupt has a separate handler function that is called from here.
+ */
+static irqreturn_t gsi_isr(int irq, void *dev_id)
+{
+	struct gsi *gsi = dev_id;
+	u32 intr_mask;
+	u32 cnt = 0;
+
+	while ((intr_mask = ioread32(gsi->virt + GSI_CNTXT_TYPE_IRQ_OFFSET))) {
+		/* intr_mask contains bitmask of pending GSI interrupts */
+		do {
+			u32 gsi_intr = BIT(__ffs(intr_mask));
+
+			intr_mask ^= gsi_intr;
+
+			switch (gsi_intr) {
+			case CH_CTRL_FMASK:
+				gsi_isr_chan_ctrl(gsi);
+				break;
+			case EV_CTRL_FMASK:
+				gsi_isr_evt_ctrl(gsi);
+				break;
+			case GLOB_EE_FMASK:
+				gsi_isr_glob_ee(gsi);
+				break;
+			case IEOB_FMASK:
+				gsi_isr_ieob(gsi);
+				break;
+			case INTER_EE_CH_CTRL_FMASK:
+				gsi_isr_inter_ee_chan_ctrl(gsi);
+				break;
+			case INTER_EE_EV_CTRL_FMASK:
+				gsi_isr_inter_ee_evt_ctrl(gsi);
+				break;
+			case GENERAL_FMASK:
+				gsi_isr_general(gsi);
+				break;
+			default:
+				dev_err(gsi->dev,
+					"%s: unrecognized type 0x%08x\n",
+					__func__, gsi_intr);
+				break;
+			}
+		} while (intr_mask);
+
+		if (++cnt > GSI_ISR_MAX_ITER) {
+			dev_err(gsi->dev, "interrupt flood\n");
+			break;
+		}
+	}
+
+	return IRQ_HANDLED;
+}
+
+/* Return the virtual address associated with a ring index */
+void *gsi_ring_virt(struct gsi_ring *ring, u32 index)
+{
+	/* Note: index *must* be used modulo the ring count here */
+	return ring->virt + (index % ring->count) * sizeof(struct gsi_tre);
+}
+
+/* Return the 32-bit DMA address associated with a ring index */
+u32 gsi_ring_addr(struct gsi_ring *ring, u32 index)
+{
+	return (ring->addr & GENMASK(31, 0)) + index * sizeof(struct gsi_tre);
+}
+
+/* Return the ring index of a 32-bit ring offset */
+static u32 gsi_ring_index(struct gsi_ring *ring, u32 offset)
+{
+	/* Code assumes channel and event ring elements are the same size */
+	BUILD_BUG_ON(sizeof(struct gsi_tre) !=
+		     sizeof(struct gsi_xfer_compl_evt));
+
+	return (offset - gsi_ring_addr(ring, 0)) / sizeof(struct gsi_tre);
+}
+
+/* Return the transaction associated with a transfer completion event */
+static struct gsi_trans *gsi_event_trans(struct gsi_channel *channel,
+					 struct gsi_xfer_compl_evt *evt)
+{
+	u32 tre_offset;
+	u32 tre_index;
+
+	/* Event xfer_ptr records the TRE it's associated with */
+	tre_offset = le64_to_cpu(evt->xfer_ptr) & GENMASK(31, 0);
+	tre_index = gsi_ring_index(&channel->tre_ring, tre_offset);
+
+	return gsi_channel_trans_mapped(channel, tre_index);
+}
+/**
+ * gsi_channel_tx_update() - Report completed TX transfers
+ * @channel:	Channel that has completed transmitting packets
+ * @trans:	Last transation known to be complete
+ *
+ * Compute the number of transactions and bytes that have been
+ * transferred on a TX channel, and report that to higher layers in
+ * the network stack for throttling.
+ */
+static void
+gsi_channel_tx_update(struct gsi_channel *channel, struct gsi_trans *trans)
+{
+	u64 byte_count = trans->byte_count + trans->len;
+	u64 trans_count = trans->trans_count + 1;
+
+	byte_count -= channel->compl_byte_count;
+	channel->compl_byte_count += byte_count;
+	trans_count -= channel->compl_trans_count;
+	channel->compl_trans_count += trans_count;;
+	/* assert(trans_count <= U32_MAX); */
+
+	ipa_gsi_channel_tx_completed(channel->gsi, gsi_channel_id(channel),
+				     trans_count, byte_count);
+}
+
+/**
+ * gsi_evt_ring_rx_update() - Record lengths of received data
+ * @evt_ring:	Event ring associated with channel that received packets
+ * @index:	Event index in ring reported by hardware
+ *
+ * Events for RX channels contain the actual number of bytes received into
+ * the buffer.  Every event has a transaction associated with it, and here
+ * we update transactions to record their actual received lengths.
+ *
+ * This function is called whenever we learn that the GSI hardware has filled
+ * new events since the last time we checked.  The ring's index field tells
+ * the first entry in need of processing.  The index provided is the
+ * first *unfilled* event in the ring (following the last filled one).
+ *
+ * Events are sequential within the event ring, and transactions are
+ * sequential within the transaction pool.
+ *
+ * Note that @index always refers to an element *within* the event ring.
+ */
+static void gsi_evt_ring_rx_update(struct gsi_evt_ring *evt_ring, u32 index)
+{
+	struct gsi_channel *channel = evt_ring->channel;
+	struct gsi_ring *ring = &evt_ring->ring;
+	struct gsi_xfer_compl_evt *evt_done;
+	struct gsi_trans_info *trans_info;
+	struct gsi_xfer_compl_evt *evt;
+	struct gsi_trans *trans;
+	u32 byte_count = 0;
+	u32 trans_avail;
+	u32 old_index;
+	u32 evt_avail;
+
+	/* We'll start with the oldest un-processed event.  RX channels
+	 * replenish receive buffers in single-TRE transactions, so we
+	 * can just map that event to its transaction.
+	 */
+	old_index = ring->index;
+	evt = gsi_ring_virt(ring, old_index);
+	trans = gsi_event_trans(channel, evt);
+
+	/* Compute the number of events to process before we wrap */
+	evt_avail = ring->count - old_index % ring->count;
+
+	/* And compute how many transactions to process before we wrap */
+	trans_info = &channel->trans_info;
+	trans_avail = (u32)(&trans_info->pool[trans_info->pool_count] - trans);
+
+	/* Finally, determine when we'll be done processing events */
+	evt_done = gsi_ring_virt(ring, index);
+	do {
+		trans->len = __le16_to_cpu(evt->len);
+		byte_count += trans->result;
+
+		if (--evt_avail)
+			evt++;
+		else
+			evt = gsi_ring_virt(ring, 0);
+
+		if (--trans_avail)
+			trans++;
+		else
+			trans = &trans_info->pool[0];
+	} while (evt != evt_done);
+
+	/* We record RX bytes when they are received */
+	channel->byte_count += byte_count;
+	channel->trans_count++;
+}
+
+/* Ring an event ring doorbell, reporting the last entry processed by the AP.
+ * The index argument (modulo the ring count) is the first unfilled entry, so
+ * we supply one less than that with the doorbell.  Update the event ring
+ * index field with the value provided.
+ */
+static void gsi_evt_ring_doorbell(struct gsi *gsi, u32 evt_ring_id, u32 index)
+{
+	struct gsi_ring *ring = &gsi->evt_ring[evt_ring_id].ring;
+	u32 val;
+
+	ring->index = index;	/* Next unused entry */
+
+	/* Note: index *must* be used modulo the ring count here */
+	val = gsi_ring_addr(ring, (index - 1) % ring->count);
+	iowrite32(val, gsi->virt + GSI_EV_CH_E_DOORBELL_0_OFFSET(evt_ring_id));
+}
+
+/* Return the maximum number of channels the hardware supports */
+static u32 gsi_channel_max(struct gsi *gsi)
+{
+	u32 val = ioread32(gsi->virt + GSI_GSI_HW_PARAM_2_OFFSET);
+
+	return u32_get_bits(val, NUM_CH_PER_EE_FMASK);
+}
+
+/* Return the maximum number of event rings the hardware supports */
+static u32 gsi_evt_ring_max(struct gsi *gsi)
+{
+	u32 val = ioread32(gsi->virt + GSI_GSI_HW_PARAM_2_OFFSET);
+
+	return u32_get_bits(val, NUM_EV_PER_EE_FMASK);
+}
+
+/* Issue a GSI command by writing a value to a register, then wait for
+ * completion to be signaled.  Reports an error if the command times out.
+ * (Timeout is not expected, and suggests broken hardware.)
+ */
+static void
+gsi_command(struct gsi *gsi, u32 reg, u32 val, struct completion *completion)
+{
+	reinit_completion(completion);
+
+	iowrite32(val, gsi->virt + reg);
+	if (!wait_for_completion_timeout(completion, GSI_CMD_TIMEOUT * HZ))
+		dev_err(gsi->dev, "%s timeout reg 0x%08x val 0x%08x\n",
+			__func__, reg, val);
+}
+
+/* Issue an event ring command and wait for it to complete */
+static void evt_ring_command(struct gsi *gsi, u32 evt_ring_id,
+			     enum gsi_evt_ch_cmd_opcode op)
+{
+	struct completion *completion = &gsi->evt_ring[evt_ring_id].completion;
+	u32 val = 0;
+
+	val |= u32_encode_bits(evt_ring_id, EV_CHID_FMASK);
+	val |= u32_encode_bits(op, EV_OPCODE_FMASK);
+
+	gsi_command(gsi, GSI_EV_CH_CMD_OFFSET, val, completion);
+}
+
+/* Issue a channel command and wait for it to complete */
+static void
+gsi_channel_command(struct gsi_channel *channel, enum gsi_ch_cmd_opcode op)
+{
+	u32 channel_id = gsi_channel_id(channel);
+	u32 val = 0;
+
+	val |= u32_encode_bits(channel_id, CH_CHID_FMASK);
+	val |= u32_encode_bits(op, CH_OPCODE_FMASK);
+
+	gsi_command(channel->gsi, GSI_CH_CMD_OFFSET, val, &channel->completion);
+}
+
+/* Initialize a ring, including allocating DMA memory for its entries */
+static int gsi_ring_alloc(struct gsi *gsi, struct gsi_ring *ring, u32 count)
+{
+	size_t size = count * sizeof(struct gsi_tre);
+	dma_addr_t addr;
+
+	BUILD_BUG_ON(!is_power_of_2(sizeof(struct gsi_tre)));
+
+	if (!count)
+		return -EINVAL;
+
+	/* Hardware requires a 2^n ring size, with alignment equal to size */
+	ring->virt = dma_alloc_coherent(gsi->dev, size, &addr, GFP_KERNEL);
+	if (ring->virt && addr % size) {
+		dma_free_coherent(gsi->dev, size, ring->virt, ring->addr);
+		dev_err(gsi->dev, "unable to alloc 0x%zx-aligned ring buffer\n",
+				size);
+		return -EINVAL;	/* Not a good error value, but distinct */
+	} else if (!ring->virt) {
+		return -ENOMEM;
+	}
+	ring->addr = addr;
+	ring->count = count;
+
+	return 0;
+}
+
+/* Free a previously-allocated ring */
+static void gsi_ring_free(struct gsi *gsi, struct gsi_ring *ring)
+{
+	size_t size = ring->count * sizeof(struct gsi_tre);
+
+	dma_free_coherent(gsi->dev, size, ring->virt, ring->addr);
+}
+
+/* Program an event ring for use */
+static void gsi_evt_ring_program(struct gsi *gsi, u32 evt_ring_id)
+{
+	struct gsi_evt_ring *evt_ring = &gsi->evt_ring[evt_ring_id];
+	size_t size = evt_ring->ring.count * sizeof(struct gsi_tre);
+	u32 val = 0;
+
+	BUILD_BUG_ON(sizeof(struct gsi_xfer_compl_evt) >
+		     field_max(EV_ELEMENT_SIZE_FMASK));
+
+	val |= u32_encode_bits(GSI_EVT_CHTYPE_GPI_EV, EV_CHTYPE_FMASK);
+	val |= EV_INTYPE_FMASK;
+	val |= u32_encode_bits(sizeof(struct gsi_xfer_compl_evt),
+			       EV_ELEMENT_SIZE_FMASK);
+	iowrite32(val, gsi->virt + GSI_EV_CH_E_CNTXT_0_OFFSET(evt_ring_id));
+
+	val = u32_encode_bits(size, EV_R_LENGTH_FMASK);
+	iowrite32(val, gsi->virt + GSI_EV_CH_E_CNTXT_1_OFFSET(evt_ring_id));
+
+	/* The context 2 and 3 registers store the low-order and
+	 * high-order 32 bits of the address of the event ring,
+	 * respectively.
+	 */
+	val = evt_ring->ring.addr & GENMASK(31, 0);
+	iowrite32(val, gsi->virt + GSI_EV_CH_E_CNTXT_2_OFFSET(evt_ring_id));
+
+	val = evt_ring->ring.addr >> 32;
+	iowrite32(val, gsi->virt + GSI_EV_CH_E_CNTXT_3_OFFSET(evt_ring_id));
+
+	/* Enable interrupt moderation by setting the moderation delay */
+	val = u32_encode_bits(IPA_GSI_EVT_RING_INT_MODT, MODT_FMASK);
+	val |= u32_encode_bits(1, MODC_FMASK);	/* comes from channel */
+	iowrite32(val, gsi->virt + GSI_EV_CH_E_CNTXT_8_OFFSET(evt_ring_id));
+
+	/* No MSI write data, and MSI address high and low address is 0 */
+	iowrite32(0, gsi->virt + GSI_EV_CH_E_CNTXT_9_OFFSET(evt_ring_id));
+	iowrite32(0, gsi->virt + GSI_EV_CH_E_CNTXT_10_OFFSET(evt_ring_id));
+	iowrite32(0, gsi->virt + GSI_EV_CH_E_CNTXT_11_OFFSET(evt_ring_id));
+
+	/* We don't need to get event read pointer updates */
+	iowrite32(0, gsi->virt + GSI_EV_CH_E_CNTXT_12_OFFSET(evt_ring_id));
+	iowrite32(0, gsi->virt + GSI_EV_CH_E_CNTXT_13_OFFSET(evt_ring_id));
+}
+
+/* Issue an allocation request to the hardware for an event ring */
+static int gsi_evt_ring_alloc_hw(struct gsi *gsi, u32 evt_ring_id)
+{
+	struct gsi_evt_ring *evt_ring = &gsi->evt_ring[evt_ring_id];
+
+	evt_ring_command(gsi, evt_ring_id, GSI_EVT_ALLOCATE);
+
+	if (evt_ring->state != GSI_EVT_RING_STATE_ALLOCATED) {
+		dev_err(gsi->dev, "evt_ring_id %u allocation bad state %u\n",
+			evt_ring_id, evt_ring->state);
+		return -EIO;
+	}
+
+	gsi_evt_ring_program(gsi, evt_ring_id);
+
+	/* Have the first event in the ring be the first one filled. */
+	gsi_evt_ring_doorbell(gsi, evt_ring_id, 0);
+
+	return 0;
+}
+
+/* Issue a hardware de-allocation request for an (allocated) event ring */
+static void gsi_evt_ring_free_hw(struct gsi *gsi, u32 evt_ring_id)
+{
+	evt_ring_command(gsi, evt_ring_id, GSI_EVT_RESET);
+
+	evt_ring_command(gsi, evt_ring_id, GSI_EVT_DE_ALLOC);
+}
+
+/* Allocate an available event ring id */
+static int gsi_evt_ring_id_alloc(struct gsi *gsi)
+{
+	u32 evt_ring_id;
+
+	if (gsi->event_bitmap == ~0U)
+		return -ENOSPC;
+
+	evt_ring_id = ffz(gsi->event_bitmap);
+	gsi->event_bitmap |= BIT(evt_ring_id);
+
+	return (int)evt_ring_id;
+}
+
+/* Free a previously-allocated event ring id */
+static void gsi_evt_ring_id_free(struct gsi *gsi, u32 evt_ring_id)
+{
+	gsi->event_bitmap &= ~BIT(evt_ring_id);
+}
+
+/* Ring a channel doorbell, reporting the first un-filled entry */
+void gsi_channel_doorbell(struct gsi_channel *channel)
+{
+	struct gsi_ring *tre_ring = &channel->tre_ring;
+	u32 channel_id = gsi_channel_id(channel);
+	struct gsi *gsi = channel->gsi;
+	u32 val;
+
+	/* Note: index *must* be used modulo the ring count here */
+	val = gsi_ring_addr(tre_ring, tre_ring->index % tre_ring->count);
+	iowrite32(val, gsi->virt + GSI_CH_C_DOORBELL_0_OFFSET(channel_id));
+}
+
+/* Consult hardware, move any newly completed transactions to completed list */
+static void gsi_channel_update(struct gsi_channel *channel)
+{
+	u32 evt_ring_id = channel->evt_ring_id;
+	struct gsi *gsi = channel->gsi;
+	struct gsi_evt_ring *evt_ring;
+	struct gsi_trans *trans;
+	struct gsi_ring *ring;
+	u32 offset;
+	u32 index;
+
+	evt_ring = &gsi->evt_ring[evt_ring_id];
+	ring = &evt_ring->ring;
+
+	/* See if there's anything new to process; if not, we're done.  Note
+	 * that index always refers to an entry *within* the event ring.
+	 */
+	offset = GSI_EV_CH_E_CNTXT_4_OFFSET(evt_ring_id);
+	index = gsi_ring_index(ring, ioread32(gsi->virt + offset));
+	if (index == ring->index % ring->count)
+		return;
+
+	/* Get the transaction for the latest completed event.  Take a
+	 * reference to keep it from completing before we give the events
+	 * for this and previous transactions back to the hardware.
+	 */
+	trans = gsi_event_trans(channel, gsi_ring_virt(ring, index - 1));
+	refcount_inc(&trans->refcount);
+
+	/* For RX channels, update each completed transaction with the number
+	 * of bytes that were actually received.  For TX channels, report
+	 * the number of transactions and bytes this completion represents
+	 * up the network stack.
+	 */
+	if (channel->toward_ipa)
+		gsi_channel_tx_update(channel, trans);
+	else
+		gsi_evt_ring_rx_update(evt_ring, index);
+
+	gsi_trans_move_complete(trans);
+
+	/* Tell the hardware we've handled these events */
+	gsi_evt_ring_doorbell(channel->gsi, channel->evt_ring_id, index);
+
+	gsi_trans_free(trans);
+}
+
+/**
+ * gsi_channel_poll_one() - Return a single completed transaction on a channel
+ * @channel:	Channel to be polled
+ *
+ * @Return:	 Transaction pointer, or null if none are available
+ *
+ * This function returns the first entry on a channel's completed transaction
+ * list.  If that list is empty, the hardware is consulted to determine
+ * whether any new transactions have completed.  If so, they're moved to the
+ * completed list and the new first entry is returned.  If there are no more
+ * completed transactions, a null pointer is returned.
+ */
+static struct gsi_trans *gsi_channel_poll_one(struct gsi_channel *channel)
+{
+	struct gsi_trans *trans;
+
+	/* Get the first transaction from the completed list */
+	trans = gsi_channel_trans_complete(channel);
+	if (!trans) {
+		/* List is empty; see if there's more to do */
+		gsi_channel_update(channel);
+		trans = gsi_channel_trans_complete(channel);
+	}
+
+	if (trans)
+		gsi_trans_move_polled(trans);
+
+	return trans;
+}
+
+/**
+ * gsi_channel_poll() - NAPI poll function for a channel
+ * @napi:	NAPI structure for the channel
+ * @budget:	Budget supplied by NAPI core
+
+ * @Return:	 Number of items polled (<= budget)
+ *
+ * Single transactions completed by hardware are polled until either
+ * the budget is exhausted, or there are no more.  Each transaction
+ * polled is passed to gsi_trans_complete(), to perform remaining
+ * completion processing and retire/free the transaction.
+ */
+static int gsi_channel_poll(struct napi_struct *napi, int budget)
+{
+	struct gsi_channel *channel;
+	int count = 0;
+
+	channel = container_of(napi, struct gsi_channel, napi);
+	while (count < budget) {
+		struct gsi_trans *trans;
+
+		trans = gsi_channel_poll_one(channel);
+		if (!trans)
+			break;
+		gsi_trans_complete(trans);
+	}
+
+	if (count < budget) {
+		napi_complete(&channel->napi);
+		gsi_irq_event_enable(channel->gsi, channel->evt_ring_id);
+	}
+
+	return count;
+}
+
+/* The event bitmap represents which event ids are available for allocation.
+ * Set bits are not available, clear bits can be used.  This function
+ * initializes the map so all events supported by the hardware are available,
+ * then precludes any reserved events from being allocated.
+ */
+static u32 gsi_event_bitmap_init(u32 evt_ring_max)
+{
+	u32 event_bitmap = GENMASK(BITS_PER_LONG - 1, evt_ring_max);
+
+	return event_bitmap | GENMASK(GSI_MHI_ER_END, GSI_MHI_ER_START);
+}
+
+/* Setup function for event rings */
+static int gsi_evt_ring_setup(struct gsi *gsi)
+{
+	u32 evt_ring_max;
+	u32 evt_ring_id;
+
+	evt_ring_max = gsi_evt_ring_max(gsi);
+	dev_dbg(gsi->dev, "evt_ring_max %u\n", evt_ring_max);
+	if (evt_ring_max != GSI_EVT_RING_MAX)
+		return -EIO;
+
+	for (evt_ring_id = 0; evt_ring_id < GSI_EVT_RING_MAX; evt_ring_id++) {
+		struct gsi_evt_ring *evt_ring = &gsi->evt_ring[evt_ring_id];
+
+		evt_ring->state = gsi_evt_ring_state(gsi, evt_ring_id);
+		if (evt_ring->state != GSI_EVT_RING_STATE_NOT_ALLOCATED)
+			return -EIO;
+	}
+
+	return 0;
+}
+
+/* Inverse of gsi_evt_ring_setup() */
+static void gsi_evt_ring_teardown(struct gsi *gsi)
+{
+	/* Nothing to do */
+}
+
+/* Configure a channel's "scratch registers" for a particular protocol */
+static void gsi_channel_scratch_write(struct gsi_channel *channel)
+{
+	u32 channel_id = gsi_channel_id(channel);
+	union gsi_channel_scratch scr = { };
+	struct gsi_gpi_channel_scratch *gpi;
+	struct gsi *gsi = channel->gsi;
+	u32 val;
+
+	/* See comments above definition of gsi_gpi_channel_scratch */
+	gpi = &scr.gpi;
+	gpi->max_outstanding_tre = channel->data->tlv_count *
+					sizeof(struct gsi_tre);
+	gpi->outstanding_threshold = 2 * sizeof(struct gsi_tre);
+
+	val = scr.data.word1;
+	iowrite32(val, gsi->virt + GSI_CH_C_SCRATCH_0_OFFSET(channel_id));
+
+	val = scr.data.word2;
+	iowrite32(val, gsi->virt + GSI_CH_C_SCRATCH_1_OFFSET(channel_id));
+
+	val = scr.data.word3;
+	iowrite32(val, gsi->virt + GSI_CH_C_SCRATCH_2_OFFSET(channel_id));
+
+	/* We must preserve the upper 16 bits of the last scratch register.
+	 * The next sequence assumes those bits remain unchanged between the
+	 * read and the write.
+	 */
+	val = ioread32(gsi->virt + GSI_CH_C_SCRATCH_3_OFFSET(channel_id));
+	val = (scr.data.word4 & GENMASK(31, 16)) | (val & GENMASK(15, 0));
+	iowrite32(val, gsi->virt + GSI_CH_C_SCRATCH_3_OFFSET(channel_id));
+}
+
+/* Program a channel for use */
+static void gsi_channel_program(struct gsi_channel *channel, bool doorbell)
+{
+	size_t size = channel->tre_ring.count * sizeof(struct gsi_tre);
+	u32 channel_id = gsi_channel_id(channel);
+	struct gsi *gsi = channel->gsi;
+	u32 wrr_weight = 0;
+	u32 val = 0;
+
+	BUILD_BUG_ON(sizeof(struct gsi_tre) > field_max(ELEMENT_SIZE_FMASK));
+
+	val |= u32_encode_bits(GSI_CHANNEL_PROTOCOL_GPI, CHTYPE_PROTOCOL_FMASK);
+	if (channel->toward_ipa)
+		val |= CHTYPE_DIR_FMASK;
+	val |= u32_encode_bits(channel->evt_ring_id, ERINDEX_FMASK);
+	val |= u32_encode_bits(sizeof(struct gsi_tre), ELEMENT_SIZE_FMASK);
+	iowrite32(val, gsi->virt + GSI_CH_C_CNTXT_0_OFFSET(channel_id));
+
+	val = u32_encode_bits(size, R_LENGTH_FMASK);
+	iowrite32(val, gsi->virt + GSI_CH_C_CNTXT_1_OFFSET(channel_id));
+
+	/* The context 2 and 3 registers store the low-order and
+	 * high-order 32 bits of the address of the channel ring,
+	 * respectively.
+	 */
+	val = channel->tre_ring.addr & GENMASK(31, 0);
+	iowrite32(val, gsi->virt + GSI_CH_C_CNTXT_2_OFFSET(channel_id));
+
+	val = channel->tre_ring.addr >> 32;
+	iowrite32(val, gsi->virt + GSI_CH_C_CNTXT_3_OFFSET(channel_id));
+
+	if (channel->data->wrr_priority)
+		wrr_weight = field_max(WRR_WEIGHT_FMASK);
+	val = u32_encode_bits(wrr_weight, WRR_WEIGHT_FMASK);
+
+	/* Max prefetch is 1 segment (do not set MAX_PREFETCH_FMASK) */
+	if (doorbell)
+		val |= USE_DB_ENG_FMASK;
+	iowrite32(val, gsi->virt + GSI_CH_C_QOS_OFFSET(channel_id));
+}
+
+/* Configure a channel; we configure all channels to use GPI protocol */
+static void gsi_channel_config(struct gsi_channel *channel, bool db_enable)
+{
+	/* Start at the first TRE entry each time we configure the channel */
+	channel->tre_ring.index = 0;
+	gsi_channel_program(channel, db_enable);
+	gsi_channel_scratch_write(channel);
+}
+
+/* Setup function for a single channel */
+static int gsi_channel_setup_one(struct gsi_channel *channel)
+{
+	u32 evt_ring_id = channel->evt_ring_id;
+	struct gsi *gsi = channel->gsi;
+	u32 val;
+	int ret;
+
+	if (!gsi)
+		return 0;	/* Ignore uninitialized channels */
+
+	channel->state = gsi_channel_state(channel);
+	if (channel->state != GSI_CHANNEL_STATE_NOT_ALLOCATED)
+		return -EIO;
+
+	mutex_lock(&gsi->mutex);
+
+	ret = gsi_evt_ring_alloc_hw(gsi, evt_ring_id);
+	if (ret)
+		goto err_mutex_unlock;
+
+	gsi_channel_command(channel, GSI_CH_ALLOCATE);
+	gsi->channel_stats.allocate++;
+
+	ret = channel->state == GSI_CHANNEL_STATE_ALLOCATED ? 0 : -EIO;
+	if (ret)
+		goto err_free_evt_ring;
+
+	gsi_channel_config(channel, true);
+
+	mutex_unlock(&gsi->mutex);
+
+	if (channel->toward_ipa)
+		netif_tx_napi_add(&gsi->dummy_dev, &channel->napi,
+				  gsi_channel_poll, NAPI_POLL_WEIGHT);
+	else
+		netif_napi_add(&gsi->dummy_dev, &channel->napi,
+			       gsi_channel_poll, NAPI_POLL_WEIGHT);
+
+	/* Enable the event interrupt (clear it first in case pending) */
+	val = BIT(evt_ring_id);
+	iowrite32(val, gsi->virt + GSI_CNTXT_SRC_IEOB_IRQ_CLR_OFFSET);
+	gsi_irq_event_enable(gsi, evt_ring_id);
+
+	return 0;
+
+err_free_evt_ring:
+	gsi_evt_ring_free_hw(gsi, evt_ring_id);
+err_mutex_unlock:
+	mutex_unlock(&gsi->mutex);
+
+	return ret;
+}
+
+/* Inverse of gsi_channel_setup_one() */
+static void gsi_channel_teardown_one(struct gsi_channel *channel)
+{
+	u32 evt_ring_id = channel->evt_ring_id;
+	struct gsi *gsi = channel->gsi;
+
+	if (!gsi)
+		return;
+
+	gsi_irq_event_disable(gsi, evt_ring_id);
+
+	netif_napi_del(&channel->napi);
+
+	mutex_lock(&gsi->mutex);
+
+	gsi_channel_command(channel, GSI_CH_DE_ALLOC);
+	gsi->channel_stats.free++;
+
+	gsi_evt_ring_free_hw(gsi, evt_ring_id);
+
+	mutex_unlock(&gsi->mutex);
+
+	gsi_channel_trans_exit(channel);
+}
+
+/* Setup function for channels */
+static int gsi_channel_setup(struct gsi *gsi)
+{
+	u32 channel_max;
+	u32 channel_id;
+	int ret;
+
+	channel_max = gsi_channel_max(gsi);
+	dev_dbg(gsi->dev, "channel_max %u\n", channel_max);
+	if (channel_max != GSI_CHANNEL_MAX)
+		return -EIO;
+
+	ret = gsi_evt_ring_setup(gsi);
+	if (ret)
+		return ret;
+
+	gsi_irq_enable(gsi);
+
+	for (channel_id = 0; channel_id < GSI_CHANNEL_MAX; channel_id++) {
+		ret = gsi_channel_setup_one(&gsi->channel[channel_id]);
+		if (ret)
+			goto err_unwind;
+	}
+
+	return 0;
+
+err_unwind:
+	while (channel_id--)
+		gsi_channel_teardown_one(&gsi->channel[channel_id]);
+	gsi_irq_enable(gsi);
+	gsi_evt_ring_teardown(gsi);
+
+	return ret;
+}
+
+/* Inverse of gsi_channel_setup() */
+static void gsi_channel_teardown(struct gsi *gsi)
+{
+	u32 channel_id;
+
+	for (channel_id = 0; channel_id < GSI_CHANNEL_MAX; channel_id++) {
+		struct gsi_channel *channel = &gsi->channel[channel_id];
+
+		gsi_channel_teardown_one(channel);
+	}
+	gsi_irq_disable(gsi);
+	gsi_evt_ring_teardown(gsi);
+}
+
+/* Setup function for GSI.  GSI firmware must be loaded and initialized */
+int gsi_setup(struct gsi *gsi)
+{
+	u32 val;
+
+	/* Here is where we first touch the GSI hardware */
+	val = ioread32(gsi->virt + GSI_GSI_STATUS_OFFSET);
+	if (!(val & ENABLED_FMASK)) {
+		dev_err(gsi->dev, "GSI has not been enabled\n");
+		return -EIO;
+	}
+
+	/* Initialize the error log */
+	iowrite32(0, gsi->virt + GSI_ERROR_LOG_OFFSET);
+
+	/* Writing 1 indicates IRQ interrupts; 0 would be MSI */
+	iowrite32(1, gsi->virt + GSI_CNTXT_INTSET_OFFSET);
+
+	return gsi_channel_setup(gsi);
+}
+
+/* Inverse of gsi_setup() */
+void gsi_teardown(struct gsi *gsi)
+{
+	gsi_channel_teardown(gsi);
+}
+
+/* Initialize a channel's event ring */
+static int gsi_channel_evt_ring_init(struct gsi_channel *channel)
+{
+	struct gsi *gsi = channel->gsi;
+	struct gsi_evt_ring *evt_ring;
+	int ret;
+
+	ret = gsi_evt_ring_id_alloc(gsi);
+	if (ret < 0)
+		return ret;
+	channel->evt_ring_id = ret;
+
+	evt_ring = &gsi->evt_ring[channel->evt_ring_id];
+	evt_ring->channel = channel;
+
+	ret = gsi_ring_alloc(gsi, &evt_ring->ring, channel->data->event_count);
+	if (ret)
+		goto err_free_evt_ring_id;
+
+	return 0;
+
+err_free_evt_ring_id:
+	gsi_evt_ring_id_free(gsi, channel->evt_ring_id);
+
+	return ret;
+}
+
+/* Inverse of gsi_channel_evt_ring_init() */
+static void gsi_channel_evt_ring_exit(struct gsi_channel *channel)
+{
+	struct gsi *gsi = channel->gsi;
+	struct gsi_evt_ring *evt_ring;
+
+	evt_ring = &gsi->evt_ring[channel->evt_ring_id];
+	gsi_ring_free(gsi, &evt_ring->ring);
+	gsi_evt_ring_id_free(gsi, channel->evt_ring_id);
+}
+
+/* Init function for event rings */
+static void gsi_evt_ring_init(struct gsi *gsi)
+{
+	u32 evt_ring_id;
+
+	BUILD_BUG_ON(GSI_EVT_RING_MAX >= BITS_PER_LONG);
+
+	gsi->event_bitmap = gsi_event_bitmap_init(GSI_EVT_RING_MAX);
+	gsi->event_enable_bitmap = 0;
+	for (evt_ring_id = 0; evt_ring_id < GSI_EVT_RING_MAX; evt_ring_id++)
+		init_completion(&gsi->evt_ring[evt_ring_id].completion);
+}
+
+/* Inverse of gsi_evt_ring_init() */
+static void gsi_evt_ring_exit(struct gsi *gsi)
+{
+	/* Nothing to do */
+}
+
+/* Init function for a single channel */
+static int
+gsi_channel_init_one(struct gsi *gsi, const struct gsi_ipa_endpoint_data *data)
+{
+	struct gsi_channel *channel;
+	int ret;
+
+	if (data->ee_id != GSI_EE_AP)
+		return 0;	/* Ignore non-AP channels */
+
+	if (data->channel_id >= GSI_CHANNEL_MAX) {
+		dev_err(gsi->dev, "bad channel id %u (must be less than %u)\n",
+			data->channel_id, GSI_CHANNEL_MAX);
+		return -EINVAL;
+	}
+
+	/* The value 256 here is arbitrary, and much higher than expected */
+	if (!data->channel.tlv_count || data->channel.tlv_count > 256) {
+		dev_err(gsi->dev, "bad tlv_count %u (must be 1..256)\n",
+			data->channel.tlv_count);
+		return -EINVAL;
+	}
+
+	if (!is_power_of_2(data->channel.tre_count)) {
+		dev_err(gsi->dev, "bad tre_count %u (must be power of 2)\n",
+			data->channel.tre_count);
+		return -EINVAL;
+	}
+
+	if (!is_power_of_2(data->channel.event_count)) {
+		dev_err(gsi->dev, "bad event_count %u (must be power of 2)\n",
+			data->channel.event_count);
+		return -EINVAL;
+	}
+
+	channel = &gsi->channel[data->channel_id];
+	memset(channel, 0, sizeof(*channel));
+
+	channel->gsi = gsi;
+	channel->toward_ipa = data->toward_ipa;
+	channel->data = &data->channel;
+
+	init_completion(&channel->completion);
+
+	ret = gsi_channel_evt_ring_init(channel);
+	if (ret)
+		return ret;
+
+	ret = gsi_ring_alloc(gsi, &channel->tre_ring, channel->data->tre_count);
+	if (ret)
+		goto err_channel_evt_ring_exit;
+
+	ret = gsi_channel_trans_init(channel);
+	if (ret)
+		goto err_ring_free;
+
+	return 0;
+
+err_ring_free:
+	gsi_ring_free(gsi, &channel->tre_ring);
+err_channel_evt_ring_exit:
+	gsi_channel_evt_ring_exit(channel);
+
+	return ret;
+}
+
+/* Inverse of gsi_channel_init_one() */
+static void gsi_channel_exit_one(struct gsi_channel *channel)
+{
+	gsi_channel_trans_exit(channel);
+	gsi_ring_free(channel->gsi, &channel->tre_ring);
+	gsi_channel_evt_ring_exit(channel);
+}
+
+/* Init function for channels */
+static int gsi_channel_init(struct gsi *gsi, u32 data_count,
+			    const struct gsi_ipa_endpoint_data *data)
+{
+	int ret = 0;
+	u32 i;
+
+	gsi_evt_ring_init(gsi);
+	for (i = 0; i < data_count; i++) {
+		ret = gsi_channel_init_one(gsi, &data[i]);
+		if (ret)
+			break;
+	}
+
+	return ret;
+}
+
+/* Inverse of gsi_channel_init() */
+static void gsi_channel_exit(struct gsi *gsi)
+{
+	u32 channel_id;
+
+	for (channel_id = 0; channel_id < GSI_CHANNEL_MAX; channel_id++)
+		gsi_channel_exit_one(&gsi->channel[channel_id]);
+	gsi_evt_ring_exit(gsi);
+}
+
+/* Init function for GSI.  GSI hardware does not need to be "ready" */
+int gsi_init(struct gsi *gsi, struct platform_device *pdev, u32 data_count,
+	     const struct gsi_ipa_endpoint_data *data)
+{
+	struct resource *res;
+	resource_size_t size;
+	unsigned int irq;
+	int ret;
+
+	gsi->dev = &pdev->dev;
+
+	/* The GSI layer performs NAPI on all endpoints.  NAPI requires a
+	 * network device structure, but the GSI layer does not have one,
+	 * so we must create a dummy network device for this purpose.
+	 */
+	init_dummy_netdev(&gsi->dummy_dev);
+
+	/* Get GSI memory range and map it */
+	res = platform_get_resource_byname(pdev, IORESOURCE_MEM, "gsi");
+	if (!res)
+		return -ENXIO;
+
+	size = resource_size(res);
+	if (res->start > U32_MAX || size > U32_MAX - res->start)
+		return -EINVAL;
+
+	gsi->virt = ioremap(res->start, size);
+	if (!gsi->virt)
+		return -ENOMEM;
+
+	mutex_init(&gsi->mutex);
+
+	ret = platform_get_irq_byname(pdev, "gsi");
+	if (ret < 0)
+		goto err_unmap_virt;
+	irq = ret;
+
+	ret = request_irq(irq, gsi_isr, 0, "gsi", gsi);
+	if (ret)
+		goto err_unmap_virt;
+	gsi->irq = irq;
+
+	ret = enable_irq_wake(gsi->irq);
+	if (ret)
+		dev_err(gsi->dev, "error %d enabling gsi wake irq\n", ret);
+	gsi->irq_wake_enabled = ret ? 0 : 1;
+
+	ret = gsi_channel_init(gsi, data_count, data);
+	if (ret)
+		goto err_mutex_destroy;
+
+	return 0;
+
+err_mutex_destroy:
+	if (gsi->irq_wake_enabled)
+		(void)disable_irq_wake(gsi->irq);
+	free_irq(gsi->irq, gsi);
+	mutex_destroy(&gsi->mutex);
+err_unmap_virt:
+	iounmap(gsi->virt);
+
+	return ret;
+}
+
+/* Inverse of gsi_init() */
+void gsi_exit(struct gsi *gsi)
+{
+	gsi_channel_exit(gsi);
+
+	if (gsi->irq_wake_enabled)
+		(void)disable_irq_wake(gsi->irq);
+	free_irq(gsi->irq, gsi);
+	mutex_destroy(&gsi->mutex);
+	iounmap(gsi->virt);
+}
+
+/* Returns the maximum number of pending transactions on a channel */
+u32 gsi_channel_trans_max(struct gsi *gsi, u32 channel_id)
+{
+	struct gsi_channel *channel = &gsi->channel[channel_id];
+
+	return channel->data->tre_count;
+}
+
+/* Returns the maximum number of TREs in a single transaction for a channel */
+u32 gsi_channel_trans_tre_max(struct gsi *gsi, u32 channel_id)
+{
+	struct gsi_channel *channel = &gsi->channel[channel_id];
+
+	return channel->data->tlv_count;
+}
+
+/* Wait for all transaction activity on a channel to complete */
+void gsi_channel_trans_quiesce(struct gsi *gsi, u32 channel_id)
+{
+	struct gsi_trans *trans;
+
+	/* Get the last transaction, and wait for it to complete */
+	trans = gsi_channel_trans_last(gsi, channel_id);
+	if (trans) {
+		wait_for_completion(&trans->completion);
+		gsi_trans_free(trans);
+	}
+}
+
+/* Make a channel operational */
+int gsi_channel_start(struct gsi *gsi, u32 channel_id)
+{
+	struct gsi_channel *channel = &gsi->channel[channel_id];
+
+	if (channel->state != GSI_CHANNEL_STATE_ALLOCATED &&
+	    channel->state != GSI_CHANNEL_STATE_STOP_IN_PROC &&
+	    channel->state != GSI_CHANNEL_STATE_STOPPED) {
+		dev_err(gsi->dev, "channel %u bad state %u\n", channel_id,
+			(u32)channel->state);
+		return -ENOTSUPP;
+	}
+
+	napi_enable(&channel->napi);
+
+	mutex_lock(&gsi->mutex);
+
+	gsi_channel_command(channel, GSI_CH_START);
+	gsi->channel_stats.start++;
+
+	mutex_unlock(&gsi->mutex);
+
+	return 0;
+}
+
+/* Stop an operational channel */
+int gsi_channel_stop(struct gsi *gsi, u32 channel_id)
+{
+	struct gsi_channel *channel = &gsi->channel[channel_id];
+	int ret;
+
+	if (channel->state == GSI_CHANNEL_STATE_STOPPED)
+		return 0;
+
+	if (channel->state != GSI_CHANNEL_STATE_STARTED &&
+	    channel->state != GSI_CHANNEL_STATE_STOP_IN_PROC &&
+	    channel->state != GSI_CHANNEL_STATE_ERROR) {
+		dev_err(gsi->dev, "channel %u bad state %u\n", channel_id,
+			(u32)channel->state);
+		return -ENOTSUPP;
+	}
+
+	gsi_channel_trans_quiesce(gsi, channel_id);
+
+	mutex_lock(&gsi->mutex);
+
+	gsi_channel_command(channel, GSI_CH_STOP);
+	gsi->channel_stats.stop++;
+
+	mutex_unlock(&gsi->mutex);
+
+	if (channel->state == GSI_CHANNEL_STATE_STOPPED)
+		ret = 0;
+	else if (channel->state == GSI_CHANNEL_STATE_STOP_IN_PROC)
+		ret = -EAGAIN;
+	else
+		ret = -EIO;
+
+	if (!ret)
+		napi_disable(&channel->napi);
+
+	return ret;
+}
+
+/* Reset and reconfigure a GSI channel (possibly leaving doorbell disabled) */
+int gsi_channel_reset(struct gsi *gsi, u32 channel_id, bool db_enable)
+{
+	struct gsi_channel *channel = &gsi->channel[channel_id];
+
+	if (channel->state != GSI_CHANNEL_STATE_STOPPED) {
+		dev_err(gsi->dev, "channel %u bad state %u\n", channel_id,
+			(u32)channel->state);
+		return -ENOTSUPP;
+	}
+
+	/* In case the reset follows stop, need to wait 1 msec */
+	usleep_range(USEC_PER_MSEC, 2 * USEC_PER_MSEC);
+
+	mutex_lock(&gsi->mutex);
+
+	gsi_channel_command(channel, GSI_CH_RESET);
+	gsi->channel_stats.reset++;
+
+	/* workaround: reset RX channels again */
+	if (!channel->toward_ipa) {
+		usleep_range(USEC_PER_MSEC, 2 * USEC_PER_MSEC);
+		gsi_channel_command(channel, GSI_CH_RESET);
+	}
+
+	gsi_channel_config(channel, db_enable);
+
+	/* Cancel pending transactions before the channel is started again */
+	gsi_channel_trans_cancel_pending(channel);
+
+	mutex_unlock(&gsi->mutex);
+
+	return 0;
+}
-- 
2.20.1