mailbox: pcc: Support HW-Reduced Communication Subspace type 2

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.

Signed-off-by: Hoan Tran <hotran@apm.com>
Reviewed-by: Prashanth Prakash <pprakash@codeaurora.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

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>
@@ -68,11 +69,16 @@
 #include "mailbox.h"
 
 #define MAX_PCC_SUBSPACES	256
+#define MBOX_IRQ_NAME		"pcc-mbox"
 
 static struct mbox_chan *pcc_mbox_channels;
 
 /* Array of cached virtual address for doorbell registers */
 static void __iomem **pcc_doorbell_vaddr;
+/* Array of cached virtual address for doorbell ack registers */
+static void __iomem **pcc_doorbell_ack_vaddr;
+/* Array of doorbell interrupts */
+static int *pcc_doorbell_irq;
 
 static struct mbox_controller pcc_mbox_ctrl = {};
 /**
@@ -91,6 +97,132 @@ static struct mbox_chan *get_pcc_channel(int id)
 	return &pcc_mbox_channels[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 *p)
+{
+	struct acpi_generic_address *doorbell_ack;
+	struct acpi_pcct_hw_reduced *pcct_ss;
+	struct mbox_chan *chan = p;
+	u64 doorbell_ack_preserve;
+	u64 doorbell_ack_write;
+	u64 doorbell_ack_val;
+	int ret;
+
+	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;
+		u32 id = chan - pcc_mbox_channels;
+
+		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_doorbell_ack_vaddr[id],
+				    &doorbell_ack_val,
+				    doorbell_ack->bit_width);
+		if (ret)
+			return IRQ_NONE;
+
+		ret = write_register(pcc_doorbell_ack_vaddr[id],
+				     (doorbell_ack_val & doorbell_ack_preserve)
+					| doorbell_ack_write,
+				     doorbell_ack->bit_width);
+		if (ret)
+			return IRQ_NONE;
+	}
+
+	return IRQ_HANDLED;
+}
+
 /**
  * pcc_mbox_request_channel - PCC clients call this function to
  *		request a pointer to their PCC subspace, from which they
@@ -135,6 +267,18 @@ 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_doorbell_irq[subspace_id] > 0) {
+		int rc;
+
+		rc = devm_request_irq(dev, pcc_doorbell_irq[subspace_id],
+				      pcc_mbox_irq, 0, MBOX_IRQ_NAME, chan);
+		if (unlikely(rc)) {
+			dev_err(dev, "failed to register PCC interrupt %d\n",
+				pcc_doorbell_irq[subspace_id]);
+			chan = ERR_PTR(rc);
+		}
+	}
+
 	spin_unlock_irqrestore(&chan->lock, flags);
 
 	return chan;
@@ -149,80 +293,30 @@ EXPORT_SYMBOL_GPL(pcc_mbox_request_channel);
  */
 void pcc_mbox_free_channel(struct mbox_chan *chan)
 {
+	u32 id = chan - pcc_mbox_channels;
 	unsigned long flags;
 
 	if (!chan || !chan->cl)
 		return;
 
+	if (id >= pcc_mbox_ctrl.num_chans) {
+		pr_debug("pcc_mbox_free_channel: Invalid mbox_chan passed\n");
+		return;
+	}
+
 	spin_lock_irqsave(&chan->lock, flags);
 	chan->cl = NULL;
 	chan->active_req = NULL;
 	if (chan->txdone_method == (TXDONE_BY_POLL | TXDONE_BY_ACK))
 		chan->txdone_method = TXDONE_BY_POLL;
 
+	if (pcc_doorbell_irq[id] > 0)
+		devm_free_irq(chan->mbox->dev, pcc_doorbell_irq[id], 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
@@ -296,8 +390,10 @@ static int parse_pcc_subspace(struct acpi_subtable_header *header,
 	if (pcc_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;
 		}
@@ -306,6 +402,43 @@ static int parse_pcc_subspace(struct acpi_subtable_header *header,
 	return 0;
 }
 
+/**
+ * pcc_parse_subspace_irq - Parse the PCC IRQ and PCC ACK register
+ *		There should be one entry per PCC client.
+ * @id: PCC subspace index.
+ * @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(int id,
+				  struct acpi_pcct_hw_reduced *pcct_ss)
+{
+	pcc_doorbell_irq[id] = pcc_map_interrupt(pcct_ss->doorbell_interrupt,
+						 (u32)pcct_ss->flags);
+	if (pcc_doorbell_irq[id] <= 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;
+
+		pcc_doorbell_ack_vaddr[id] = acpi_os_ioremap(
+				pcct2_ss->doorbell_ack_register.address,
+				pcct2_ss->doorbell_ack_register.bit_width / 8);
+		if (!pcc_doorbell_ack_vaddr[id]) {
+			pr_err("Failed to ioremap PCC ACK register\n");
+			return -ENOMEM;
+		}
+	}
+
+	return 0;
+}
+
 /**
  * acpi_pcc_probe - Parse the ACPI tree for the PCCT.
  *
@@ -316,7 +449,9 @@ 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;
+	int sum = 0;
 	acpi_status status = AE_OK;
 
 	/* Search for PCCT */
@@ -333,37 +468,66 @@ static int __init acpi_pcc_probe(void)
 			sizeof(struct acpi_table_pcct),
 			ACPI_PCCT_TYPE_HW_REDUCED_SUBSPACE,
 			parse_pcc_subspace, MAX_PCC_SUBSPACES);
+	sum += (count > 0) ? count : 0;
+
+	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);
+	sum += (count > 0) ? count : 0;
 
-	if (count <= 0) {
+	if (sum == 0 || sum >= MAX_PCC_SUBSPACES) {
 		pr_err("Error parsing PCC subspaces from PCCT\n");
 		return -EINVAL;
 	}
 
 	pcc_mbox_channels = kzalloc(sizeof(struct mbox_chan) *
-			count, GFP_KERNEL);
-
+			sum, GFP_KERNEL);
 	if (!pcc_mbox_channels) {
 		pr_err("Could not allocate space for PCC mbox channels\n");
 		return -ENOMEM;
 	}
 
-	pcc_doorbell_vaddr = kcalloc(count, sizeof(void *), GFP_KERNEL);
+	pcc_doorbell_vaddr = kcalloc(sum, sizeof(void *), GFP_KERNEL);
 	if (!pcc_doorbell_vaddr) {
-		kfree(pcc_mbox_channels);
-		return -ENOMEM;
+		rc = -ENOMEM;
+		goto err_free_mbox;
+	}
+
+	pcc_doorbell_ack_vaddr = kcalloc(sum, sizeof(void *), GFP_KERNEL);
+	if (!pcc_doorbell_ack_vaddr) {
+		rc = -ENOMEM;
+		goto err_free_db_vaddr;
+	}
+
+	pcc_doorbell_irq = kcalloc(sum, sizeof(int), GFP_KERNEL);
+	if (!pcc_doorbell_irq) {
+		rc = -ENOMEM;
+		goto err_free_db_ack_vaddr;
 	}
 
 	/* Point to the first PCC subspace entry */
 	pcct_entry = (struct acpi_subtable_header *) (
 		(unsigned long) pcct_tbl + sizeof(struct acpi_table_pcct));
 
-	for (i = 0; i < count; i++) {
+	acpi_pcct_tbl = (struct acpi_table_pcct *) pcct_tbl;
+	if (acpi_pcct_tbl->flags & ACPI_PCCT_DOORBELL)
+		pcc_mbox_ctrl.txdone_irq = true;
+
+	for (i = 0; i < sum; i++) {
 		struct acpi_generic_address *db_reg;
 		struct acpi_pcct_hw_reduced *pcct_ss;
 		pcc_mbox_channels[i].con_priv = pcct_entry;
 
+		pcct_ss = (struct acpi_pcct_hw_reduced *) pcct_entry;
+
+		if (pcc_mbox_ctrl.txdone_irq) {
+			rc = pcc_parse_subspace_irq(i, pcct_ss);
+			if (rc < 0)
+				goto err;
+		}
+
 		/* 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,
@@ -372,11 +536,21 @@ static int __init acpi_pcc_probe(void)
 			((unsigned long) pcct_entry + pcct_entry->length);
 	}
 
-	pcc_mbox_ctrl.num_chans = count;
+	pcc_mbox_ctrl.num_chans = sum;
 
 	pr_info("Detected %d PCC Subspaces\n", pcc_mbox_ctrl.num_chans);
 
 	return 0;
+
+err:
+	kfree(pcc_doorbell_irq);
+err_free_db_ack_vaddr:
+	kfree(pcc_doorbell_ack_vaddr);
+err_free_db_vaddr:
+	kfree(pcc_doorbell_vaddr);
+err_free_mbox:
+	kfree(pcc_mbox_channels);
+	return rc;
 }
 
 /**