[PATCH v2] mailbox: pcc: Support HW-Reduced Communication Subspace Type 2

[Hoan Tran]

From: hotran <hotran@xxxxxxx>

ACPI 6.1 has a PCC HW-Reduced Communication Subspace Type 2 intended for
use on HW-Reduce ACPI Platform, which requires read-modify-write sequence
to acknowledge doorbell interrupt. This patch provides the implementation
for the Communication Subspace Type 2.

This patch depends on patch [1] which supports PCC subspace type 2 header
[1] https://lkml.org/lkml/2016/5/5/14
 - [PATCH v2 03/13] ACPICA: ACPI 6.1: Support for new PCCT subtable

v2
 * Remove changes inside "actbl3.h". This file is taken care by ACPICA.
 * Parse both subspace type 1 and subspace type 2
 * Remove unnecessary variable initialization
 * ISR returns IRQ_NONE in case of error

v1
 * Initial

Signed-off-by: Hoan Tran <hotran@xxxxxxx>
---
 drivers/mailbox/pcc.c | 395 +++++++++++++++++++++++++++++++++++++-------------
 1 file changed, 296 insertions(+), 99 deletions(-)

diff --git a/drivers/mailbox/pcc.c b/drivers/mailbox/pcc.c
index 043828d..58c9a67 100644
--- a/drivers/mailbox/pcc.c
+++ b/drivers/mailbox/pcc.c
@@ -59,6 +59,7 @@
 #include <linux/delay.h>
 #include <linux/io.h>
 #include <linux/init.h>
+#include <linux/interrupt.h>
 #include <linux/list.h>
 #include <linux/platform_device.h>
 #include <linux/mailbox_controller.h>
@@ -68,27 +69,179 @@
 #include "mailbox.h"
 
 #define MAX_PCC_SUBSPACES	256
+#define MBOX_IRQ_NAME		"pcc-mbox"
 
-static struct mbox_chan *pcc_mbox_channels;
+/**
+ * PCC mailbox channel information
+ *
+ * @chan:	Pointer to mailbox communication channel
+ * @pcc_doorbell_vaddr: PCC doorbell register address
+ * @pcc_doorbell_ack_vaddr: PCC doorbell ack register address
+ * @irq:	Interrupt number of the channel
+ */
+struct pcc_mbox_chan {
+	struct mbox_chan	*chan;
+	void __iomem		*pcc_doorbell_vaddr;
+	void __iomem		*pcc_doorbell_ack_vaddr;
+	int			irq;
+};
 
-/* Array of cached virtual address for doorbell registers */
-static void __iomem **pcc_doorbell_vaddr;
+/**
+ * PCC mailbox controller data
+ *
+ * @mb_ctrl:	Representation of the communication channel controller
+ * @mbox_chan:	Array of PCC mailbox channels of the controller
+ * @chans:	Array of mailbox communication channels
+ */
+struct pcc_mbox {
+	struct mbox_controller	mbox_ctrl;
+	struct pcc_mbox_chan	*mbox_chans;
+	struct mbox_chan	*chans;
+};
+
+static struct pcc_mbox pcc_mbox_ctx = {};
 
-static struct mbox_controller pcc_mbox_ctrl = {};
 /**
  * get_pcc_channel - Given a PCC subspace idx, get
- *	the respective mbox_channel.
+ *	the respective pcc mbox_channel.
  * @id: PCC subspace index.
  *
  * Return: ERR_PTR(errno) if error, else pointer
- *	to mbox channel.
+ *	to pcc mbox channel.
  */
-static struct mbox_chan *get_pcc_channel(int id)
+static struct pcc_mbox_chan *get_pcc_channel(int id)
 {
-	if (id < 0 || id > pcc_mbox_ctrl.num_chans)
+	if (id < 0 || id > pcc_mbox_ctx.mbox_ctrl.num_chans)
 		return ERR_PTR(-ENOENT);
 
-	return &pcc_mbox_channels[id];
+	return &pcc_mbox_ctx.mbox_chans[id];
+}
+
+/*
+ * PCC can be used with perf critical drivers such as CPPC
+ * So it makes sense to locally cache the virtual address and
+ * use it to read/write to PCC registers such as doorbell register
+ *
+ * The below read_register and write_registers are used to read and
+ * write from perf critical registers such as PCC doorbell register
+ */
+static int read_register(void __iomem *vaddr, u64 *val, unsigned int bit_width)
+{
+	int ret_val = 0;
+
+	switch (bit_width) {
+	case 8:
+		*val = readb(vaddr);
+		break;
+	case 16:
+		*val = readw(vaddr);
+		break;
+	case 32:
+		*val = readl(vaddr);
+		break;
+	case 64:
+		*val = readq(vaddr);
+		break;
+	default:
+		pr_debug("Error: Cannot read register of %u bit width",
+			bit_width);
+		ret_val = -EFAULT;
+		break;
+	}
+	return ret_val;
+}
+
+static int write_register(void __iomem *vaddr, u64 val, unsigned int bit_width)
+{
+	int ret_val = 0;
+
+	switch (bit_width) {
+	case 8:
+		writeb(val, vaddr);
+		break;
+	case 16:
+		writew(val, vaddr);
+		break;
+	case 32:
+		writel(val, vaddr);
+		break;
+	case 64:
+		writeq(val, vaddr);
+		break;
+	default:
+		pr_debug("Error: Cannot write register of %u bit width",
+			bit_width);
+		ret_val = -EFAULT;
+		break;
+	}
+	return ret_val;
+}
+
+/**
+ * pcc_map_interrupt - Map a PCC subspace GSI to a linux IRQ number
+ * @interrupt: GSI number.
+ * @flags: interrupt flags
+ *
+ * Returns: a valid linux IRQ number on success
+ *		0 or -EINVAL on failure
+ */
+static int pcc_map_interrupt(u32 interrupt, u32 flags)
+{
+	int trigger, polarity;
+
+	if (!interrupt)
+		return 0;
+
+	trigger = (flags & ACPI_PCCT_INTERRUPT_MODE) ? ACPI_EDGE_SENSITIVE
+			: ACPI_LEVEL_SENSITIVE;
+
+	polarity = (flags & ACPI_PCCT_INTERRUPT_POLARITY) ? ACPI_ACTIVE_LOW
+			: ACPI_ACTIVE_HIGH;
+
+	return acpi_register_gsi(NULL, interrupt, trigger, polarity);
+}
+
+/**
+ * pcc_mbox_irq - PCC mailbox interrupt handler
+ */
+static irqreturn_t pcc_mbox_irq(int irq, void *id)
+{
+	struct acpi_generic_address *doorbell_ack;
+	struct acpi_pcct_hw_reduced *pcct_ss;
+	struct pcc_mbox_chan *pcc_chan = id;
+	u64 doorbell_ack_preserve;
+	struct mbox_chan *chan;
+	u64 doorbell_ack_write;
+	u64 doorbell_ack_val;
+	int ret;
+
+	chan = pcc_chan->chan;
+	pcct_ss = chan->con_priv;
+
+	mbox_chan_received_data(chan, NULL);
+
+	if (pcct_ss->header.type == ACPI_PCCT_TYPE_HW_REDUCED_SUBSPACE_TYPE2) {
+		struct acpi_pcct_hw_reduced_type2 *pcct2_ss = chan->con_priv;
+
+		doorbell_ack = &pcct2_ss->doorbell_ack_register;
+		doorbell_ack_preserve = pcct2_ss->ack_preserve_mask;
+		doorbell_ack_write = pcct2_ss->ack_write_mask;
+
+		ret = read_register(pcc_chan->pcc_doorbell_ack_vaddr,
+				    &doorbell_ack_val,
+				    doorbell_ack->bit_width);
+		if (ret)
+			return IRQ_NONE;
+
+		ret = write_register(pcc_chan->pcc_doorbell_ack_vaddr,
+				     (doorbell_ack_val & doorbell_ack_preserve)
+					| doorbell_ack_write,
+				     doorbell_ack->bit_width);
+		if (ret)
+			return IRQ_NONE;
+	}
+
+	return IRQ_HANDLED;
 }
 
 /**
@@ -107,7 +260,8 @@ static struct mbox_chan *get_pcc_channel(int id)
 struct mbox_chan *pcc_mbox_request_channel(struct mbox_client *cl,
 		int subspace_id)
 {
-	struct device *dev = pcc_mbox_ctrl.dev;
+	struct device *dev = pcc_mbox_ctx.mbox_ctrl.dev;
+	struct pcc_mbox_chan *pcc_chan;
 	struct mbox_chan *chan;
 	unsigned long flags;
 
@@ -118,8 +272,13 @@ struct mbox_chan *pcc_mbox_request_channel(struct mbox_client *cl,
 	 * This returns a pointer to the PCC subspace
 	 * for the Client to operate on.
 	 */
-	chan = get_pcc_channel(subspace_id);
+	pcc_chan = get_pcc_channel(subspace_id);
+	if (IS_ERR(pcc_chan)) {
+		dev_err(dev, "PCC Channel not found for idx: %d\n", subspace_id);
+		return ERR_PTR(-EBUSY);
+	}
 
+	chan = pcc_chan->chan;
 	if (IS_ERR(chan) || chan->cl) {
 		dev_err(dev, "Channel not found for idx: %d\n", subspace_id);
 		return ERR_PTR(-EBUSY);
@@ -135,6 +294,18 @@ struct mbox_chan *pcc_mbox_request_channel(struct mbox_client *cl,
 	if (chan->txdone_method == TXDONE_BY_POLL && cl->knows_txdone)
 		chan->txdone_method |= TXDONE_BY_ACK;
 
+	if (pcc_chan->irq > 0) {
+		int rc;
+
+		rc = devm_request_irq(dev, pcc_chan->irq, pcc_mbox_irq, 0,
+				      MBOX_IRQ_NAME, pcc_chan);
+		if (unlikely(rc)) {
+			dev_err(dev, "failed to register PCC interrupt %d\n",
+				pcc_chan->irq);
+			chan = ERR_PTR(rc);
+		}
+	}
+
 	spin_unlock_irqrestore(&chan->lock, flags);
 
 	return chan;
@@ -149,7 +320,9 @@ EXPORT_SYMBOL_GPL(pcc_mbox_request_channel);
  */
 void pcc_mbox_free_channel(struct mbox_chan *chan)
 {
+	struct pcc_mbox_chan *pcc_chan;
 	unsigned long flags;
+	u32 id;
 
 	if (!chan || !chan->cl)
 		return;
@@ -160,69 +333,19 @@ void pcc_mbox_free_channel(struct mbox_chan *chan)
 	if (chan->txdone_method == (TXDONE_BY_POLL | TXDONE_BY_ACK))
 		chan->txdone_method = TXDONE_BY_POLL;
 
+	id = chan - pcc_mbox_ctx.chans;
+	pcc_chan = get_pcc_channel(id);
+	if (IS_ERR(pcc_chan)) {
+		pr_debug("PCC Channel not found for idx: %d\n", id);
+	} else {
+		if (pcc_chan->irq > 0)
+			devm_free_irq(chan->mbox->dev, pcc_chan->irq, chan);
+	}
+
 	spin_unlock_irqrestore(&chan->lock, flags);
 }
 EXPORT_SYMBOL_GPL(pcc_mbox_free_channel);
 
-/*
- * PCC can be used with perf critical drivers such as CPPC
- * So it makes sense to locally cache the virtual address and
- * use it to read/write to PCC registers such as doorbell register
- *
- * The below read_register and write_registers are used to read and
- * write from perf critical registers such as PCC doorbell register
- */
-static int read_register(void __iomem *vaddr, u64 *val, unsigned int bit_width)
-{
-	int ret_val = 0;
-
-	switch (bit_width) {
-	case 8:
-		*val = readb(vaddr);
-		break;
-	case 16:
-		*val = readw(vaddr);
-		break;
-	case 32:
-		*val = readl(vaddr);
-		break;
-	case 64:
-		*val = readq(vaddr);
-		break;
-	default:
-		pr_debug("Error: Cannot read register of %u bit width",
-			bit_width);
-		ret_val = -EFAULT;
-		break;
-	}
-	return ret_val;
-}
-
-static int write_register(void __iomem *vaddr, u64 val, unsigned int bit_width)
-{
-	int ret_val = 0;
-
-	switch (bit_width) {
-	case 8:
-		writeb(val, vaddr);
-		break;
-	case 16:
-		writew(val, vaddr);
-		break;
-	case 32:
-		writel(val, vaddr);
-		break;
-	case 64:
-		writeq(val, vaddr);
-		break;
-	default:
-		pr_debug("Error: Cannot write register of %u bit width",
-			bit_width);
-		ret_val = -EFAULT;
-		break;
-	}
-	return ret_val;
-}
 
 /**
  * pcc_send_data - Called from Mailbox Controller code. Used
@@ -240,36 +363,44 @@ static int pcc_send_data(struct mbox_chan *chan, void *data)
 {
 	struct acpi_pcct_hw_reduced *pcct_ss = chan->con_priv;
 	struct acpi_generic_address *doorbell;
+	struct pcc_mbox_chan *pcc_chan;
 	u64 doorbell_preserve;
 	u64 doorbell_val;
 	u64 doorbell_write;
-	u32 id = chan - pcc_mbox_channels;
-	int ret = 0;
+	u32 id = chan - pcc_mbox_ctx.chans;
+	int ret;
 
-	if (id >= pcc_mbox_ctrl.num_chans) {
+	if (id >= pcc_mbox_ctx.mbox_ctrl.num_chans) {
 		pr_debug("pcc_send_data: Invalid mbox_chan passed\n");
 		return -ENOENT;
 	}
 
+	pcc_chan = get_pcc_channel(id);
+	if (IS_ERR(pcc_chan)) {
+		pr_debug("PCC Channel not found for idx: %d\n", id);
+		return -EBUSY;
+	}
+
 	doorbell = &pcct_ss->doorbell_register;
 	doorbell_preserve = pcct_ss->preserve_mask;
 	doorbell_write = pcct_ss->write_mask;
 
 	/* Sync notification from OS to Platform. */
-	if (pcc_doorbell_vaddr[id]) {
-		ret = read_register(pcc_doorbell_vaddr[id], &doorbell_val,
-			doorbell->bit_width);
+	if (pcc_chan->pcc_doorbell_vaddr) {
+		ret = read_register(pcc_chan->pcc_doorbell_vaddr, &doorbell_val,
+				    doorbell->bit_width);
 		if (ret)
 			return ret;
-		ret = write_register(pcc_doorbell_vaddr[id],
-			(doorbell_val & doorbell_preserve) | doorbell_write,
-			doorbell->bit_width);
+		ret = write_register(pcc_chan->pcc_doorbell_vaddr,
+				     (doorbell_val & doorbell_preserve)
+					| doorbell_write,
+				     doorbell->bit_width);
 	} else {
 		ret = acpi_read(&doorbell_val, doorbell);
 		if (ret)
 			return ret;
 		ret = acpi_write((doorbell_val & doorbell_preserve) | doorbell_write,
-			doorbell);
+				 doorbell);
 	}
 	return ret;
 }
@@ -293,11 +424,13 @@ static int parse_pcc_subspace(struct acpi_subtable_header *header,
 {
 	struct acpi_pcct_hw_reduced *pcct_ss;
 
-	if (pcc_mbox_ctrl.num_chans <= MAX_PCC_SUBSPACES) {
+	if (pcc_mbox_ctx.mbox_ctrl.num_chans <= MAX_PCC_SUBSPACES) {
 		pcct_ss = (struct acpi_pcct_hw_reduced *) header;
 
-		if (pcct_ss->header.type !=
-				ACPI_PCCT_TYPE_HW_REDUCED_SUBSPACE) {
+		if ((pcct_ss->header.type !=
+				ACPI_PCCT_TYPE_HW_REDUCED_SUBSPACE)
+		    && (pcct_ss->header.type !=
+				ACPI_PCCT_TYPE_HW_REDUCED_SUBSPACE_TYPE2)) {
 			pr_err("Incorrect PCC Subspace type detected\n");
 			return -EINVAL;
 		}
@@ -307,6 +440,43 @@ static int parse_pcc_subspace(struct acpi_subtable_header *header,
 }
 
 /**
+ * pcc_parse_subspace_irq - Parse the PCC IRQ and PCC ACK register
+ *		There should be one entry per PCC client.
+ * @mbox_chans: Pointer to the PCC mailbox channel data
+ * @pcct_ss: Pointer to the ACPI subtable header under the PCCT.
+ *
+ * Return: 0 for Success, else errno.
+ *
+ * This gets called for each entry in the PCC table.
+ */
+static int pcc_parse_subspace_irq(struct pcc_mbox_chan *mbox_chans,
+		struct acpi_pcct_hw_reduced *pcct_ss)
+{
+	mbox_chans->irq = pcc_map_interrupt(pcct_ss->doorbell_interrupt,
+					    (u32)pcct_ss->flags);
+	if (mbox_chans->irq <= 0) {
+		pr_err("PCC GSI %d not registered\n",
+		       pcct_ss->doorbell_interrupt);
+		return -EINVAL;
+	}
+
+	if (pcct_ss->header.type
+		== ACPI_PCCT_TYPE_HW_REDUCED_SUBSPACE_TYPE2) {
+		struct acpi_pcct_hw_reduced_type2 *pcct2_ss = (void *)pcct_ss;
+
+		mbox_chans->pcc_doorbell_ack_vaddr = acpi_os_ioremap(
+				pcct2_ss->doorbell_ack_register.address,
+				pcct2_ss->doorbell_ack_register.bit_width / 8);
+		if (!mbox_chans->pcc_doorbell_ack_vaddr) {
+			pr_err("Failed to ioremap PCC ACK register\n");
+			return -ENOMEM;
+		}
+	}
+
+	return 0;
+}
+
+/**
  * acpi_pcc_probe - Parse the ACPI tree for the PCCT.
  *
  * Return: 0 for Success, else errno.
@@ -316,7 +486,8 @@ static int __init acpi_pcc_probe(void)
 	acpi_size pcct_tbl_header_size;
 	struct acpi_table_header *pcct_tbl;
 	struct acpi_subtable_header *pcct_entry;
-	int count, i;
+	struct acpi_table_pcct *acpi_pcct_tbl;
+	int count, i, rc;
 	acpi_status status = AE_OK;
 
 	/* Search for PCCT */
@@ -334,22 +505,28 @@ static int __init acpi_pcc_probe(void)
 			ACPI_PCCT_TYPE_HW_REDUCED_SUBSPACE,
 			parse_pcc_subspace, MAX_PCC_SUBSPACES);
 
+	count += acpi_table_parse_entries(ACPI_SIG_PCCT,
+			sizeof(struct acpi_table_pcct),
+			ACPI_PCCT_TYPE_HW_REDUCED_SUBSPACE_TYPE2,
+			parse_pcc_subspace, MAX_PCC_SUBSPACES);
+
 	if (count <= 0) {
 		pr_err("Error parsing PCC subspaces from PCCT\n");
 		return -EINVAL;
 	}
 
-	pcc_mbox_channels = kzalloc(sizeof(struct mbox_chan) *
-			count, GFP_KERNEL);
+	pcc_mbox_ctx.chans = kzalloc(sizeof(struct mbox_chan) *
+				     count, GFP_KERNEL);
 
-	if (!pcc_mbox_channels) {
+	if (!pcc_mbox_ctx.chans) {
 		pr_err("Could not allocate space for PCC mbox channels\n");
 		return -ENOMEM;
 	}
 
-	pcc_doorbell_vaddr = kcalloc(count, sizeof(void *), GFP_KERNEL);
-	if (!pcc_doorbell_vaddr) {
-		kfree(pcc_mbox_channels);
+	pcc_mbox_ctx.mbox_chans = kzalloc(sizeof(struct pcc_mbox_chan) *
+					  count, GFP_KERNEL);
+	if (!pcc_mbox_ctx.mbox_chans) {
+		pr_err("Could not allocate space for PCC mbox channel data\n");
 		return -ENOMEM;
 	}
 
@@ -357,24 +534,44 @@ static int __init acpi_pcc_probe(void)
 	pcct_entry = (struct acpi_subtable_header *) (
 		(unsigned long) pcct_tbl + sizeof(struct acpi_table_pcct));
 
+	acpi_pcct_tbl = (struct acpi_table_pcct *) pcct_tbl;
+	if (acpi_pcct_tbl->flags & ACPI_PCCT_DOORBELL)
+		pcc_mbox_ctx.mbox_ctrl.txdone_irq = true;
+
 	for (i = 0; i < count; i++) {
 		struct acpi_generic_address *db_reg;
 		struct acpi_pcct_hw_reduced *pcct_ss;
-		pcc_mbox_channels[i].con_priv = pcct_entry;
+
+		pcc_mbox_ctx.chans[i].con_priv = pcct_entry;
+		pcc_mbox_ctx.chans[i].mbox = &pcc_mbox_ctx.mbox_ctrl;
+
+		pcct_ss = (struct acpi_pcct_hw_reduced *) pcct_entry;
+
+		pcc_mbox_ctx.mbox_chans[i].chan = &pcc_mbox_ctx.chans[i];
+		if (pcc_mbox_ctx.mbox_ctrl.txdone_irq) {
+			rc = pcc_parse_subspace_irq(&pcc_mbox_ctx.mbox_chans[i],
+						    pcct_ss);
+			if (rc < 0)
+				return rc;
+		}
 
 		/* If doorbell is in system memory cache the virt address */
 		pcct_ss = (struct acpi_pcct_hw_reduced *)pcct_entry;
 		db_reg = &pcct_ss->doorbell_register;
-		if (db_reg->space_id == ACPI_ADR_SPACE_SYSTEM_MEMORY)
-			pcc_doorbell_vaddr[i] = acpi_os_ioremap(db_reg->address,
+		if (db_reg->space_id == ACPI_ADR_SPACE_SYSTEM_MEMORY) {
+			pcc_mbox_ctx.mbox_chans[i].pcc_doorbell_vaddr =
+					acpi_os_ioremap(db_reg->address,
 							db_reg->bit_width/8);
+		}
+
 		pcct_entry = (struct acpi_subtable_header *)
 			((unsigned long) pcct_entry + pcct_entry->length);
 	}
 
-	pcc_mbox_ctrl.num_chans = count;
+	pcc_mbox_ctx.mbox_ctrl.num_chans = count;
 
-	pr_info("Detected %d PCC Subspaces\n", pcc_mbox_ctrl.num_chans);
+	pr_info("Detected %d PCC Subspaces\n",
+		pcc_mbox_ctx.mbox_ctrl.num_chans);
 
 	return 0;
 }
@@ -394,12 +591,12 @@ static int pcc_mbox_probe(struct platform_device *pdev)
 {
 	int ret = 0;
 
-	pcc_mbox_ctrl.chans = pcc_mbox_channels;
-	pcc_mbox_ctrl.ops = &pcc_chan_ops;
-	pcc_mbox_ctrl.dev = &pdev->dev;
+	pcc_mbox_ctx.mbox_ctrl.chans = pcc_mbox_ctx.chans;
+	pcc_mbox_ctx.mbox_ctrl.ops = &pcc_chan_ops;
+	pcc_mbox_ctx.mbox_ctrl.dev = &pdev->dev;
 
 	pr_info("Registering PCC driver as Mailbox controller\n");
-	ret = mbox_controller_register(&pcc_mbox_ctrl);
+	ret = mbox_controller_register(&pcc_mbox_ctx.mbox_ctrl);
 
 	if (ret) {
 		pr_err("Err registering PCC as Mailbox controller: %d\n", ret);
-- 
1.9.1


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