[PATCH 6/7] spmi: apple: use IRQ for RX FIFO if possible

[Sasha Finkelstein]

From: Alba Mendez <me@xxxxxxx>

The IRQ fires as soon as the reply is available, which is usually takes
a few us instead of the 10ms sleep interval for polling

Signed-off-by: Alba Mendez <me@xxxxxxx>
Signed-off-by: Sasha Finkelstein <k@xxxxxxxxxxxxxx>
---
 drivers/spmi/spmi-apple-controller.c | 97 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 96 insertions(+), 1 deletion(-)

diff --git a/drivers/spmi/spmi-apple-controller.c b/drivers/spmi/spmi-apple-controller.c
index d8509f027df6..d627187b3ac0 100644
--- a/drivers/spmi/spmi-apple-controller.c
+++ b/drivers/spmi/spmi-apple-controller.c
@@ -11,6 +11,8 @@
  *		spmi-pmic-arb.c Copyright (c) 2021, The Linux Foundation.
  */
 
+#include <linux/completion.h>
+#include <linux/interrupt.h>
 #include <linux/io.h>
 #include <linux/iopoll.h>
 #include <linux/module.h>
@@ -23,6 +25,12 @@
 #define SPMI_CMD_REG 0x4
 #define SPMI_RSP_REG 0x8
 
+#define SPMI_IRQ_MASK_BASE 0x20
+#define SPMI_IRQ_ACK_BASE 0x60
+#define SPMI_IRQ_USER_SIZE 0x20
+
+#define SPMI_IRQ_FIFO_RX 0
+
 /* SPMI_RSP_REG reply word */
 #define SPMI_REPLY_FRAME_PARITY_OFFSET 16
 #define SPMI_REPLY_ACK BIT(15)
@@ -37,6 +45,8 @@
 struct apple_spmi {
 	void __iomem *regs;
 	struct mutex fifo_lock;
+	bool fifo_rx_irq;
+	struct completion fifo_rx;
 };
 
 #define poll_reg(spmi, reg, val, cond) \
@@ -55,7 +65,19 @@ static int apple_spmi_wait_rx_not_empty(struct spmi_controller *ctrl)
 	int ret;
 	u32 status;
 
-	ret = poll_reg(spmi, SPMI_STATUS_REG, status, !(status & SPMI_RX_FIFO_EMPTY));
+	if (spmi->fifo_rx_irq) {
+		ret = wait_for_completion_timeout(&spmi->fifo_rx,
+			usecs_to_jiffies(REG_POLL_TIMEOUT_US));
+		if (!ret)
+			ret = -ETIMEDOUT;
+		else if (readl(spmi->regs + SPMI_STATUS_REG) & SPMI_RX_FIFO_EMPTY)
+			ret = -EIO;
+		else
+			ret = 0;
+	} else {
+		ret = poll_reg(spmi, SPMI_STATUS_REG, status, !(status & SPMI_RX_FIFO_EMPTY));
+	}
+
 	if (ret) {
 		dev_err(&ctrl->dev,
 			"failed to wait for RX FIFO not empty\n");
@@ -79,6 +101,8 @@ static int spmi_raw_cmd(struct spmi_controller *ctrl, u8 opc, u8 sid,
 	if (ret)
 		return ret;
 
+	reinit_completion(&spmi->fifo_rx);
+
 	writel(spmi_cmd, spmi->regs + SPMI_CMD_REG);
 
 	while (i < len) {
@@ -183,10 +207,68 @@ static int spmi_cmd(struct spmi_controller *ctrl, u8 opc, u8 sid)
 	return -EINVAL;
 }
 
+static void apple_spmi_irq_ack_raw(struct apple_spmi *spmi, u32 irq)
+{
+	u32 __iomem *reg = spmi->regs + SPMI_IRQ_ACK_BASE + (irq / 32) * 4;
+
+	writel(BIT(irq % 32), reg);
+}
+
+static void apple_spmi_irq_mask_raw(struct apple_spmi *spmi, u32 irq)
+{
+	u32 __iomem *reg = spmi->regs + SPMI_IRQ_MASK_BASE + (irq / 32) * 4;
+
+	writel(readl(reg) & ~BIT(irq % 32), reg);
+}
+
+static void apple_spmi_irq_unmask_raw(struct apple_spmi *spmi, u32 irq)
+{
+	u32 __iomem *reg = spmi->regs + SPMI_IRQ_MASK_BASE + (irq / 32) * 4;
+
+	writel(readl(reg) | BIT(irq % 32), reg);
+}
+
+static irqreturn_t apple_spmi_irq_handler(int irq, void *dev_id)
+{
+	struct apple_spmi *spmi = dev_id;
+	bool handled = false;
+	u32 val, offset, bit;
+
+	val = readl(spmi->regs + SPMI_IRQ_ACK_BASE + SPMI_IRQ_USER_SIZE);
+	if (val & BIT(SPMI_IRQ_FIFO_RX)) {
+		complete(&spmi->fifo_rx);
+		apple_spmi_irq_ack_raw(spmi, SPMI_IRQ_USER_SIZE * 8 + SPMI_IRQ_FIFO_RX);
+		handled = true;
+	}
+
+	return handled ? IRQ_HANDLED : IRQ_NONE;
+}
+
+static int apple_spmi_init_irq(struct platform_device *pdev,
+			  struct apple_spmi *spmi, int irq)
+{
+	int ret;
+
+	for (size_t offset = 0; offset < SPMI_IRQ_USER_SIZE + 4; offset += 4) {
+		writel(0, spmi->regs + SPMI_IRQ_MASK_BASE + offset);
+		writel(U32_MAX, spmi->regs + SPMI_IRQ_ACK_BASE + offset);
+	}
+
+	spmi->fifo_rx_irq = true;
+	apple_spmi_irq_unmask_raw(spmi, SPMI_IRQ_USER_SIZE * 8 + SPMI_IRQ_FIFO_RX);
+
+	ret = devm_request_any_context_irq(&pdev->dev, irq, apple_spmi_irq_handler, 0, NULL, spmi);
+	if (ret < 0)
+		return dev_err_probe(&pdev->dev, ret, "failed to request IRQ\n");
+
+	return 0;
+}
+
 static int apple_spmi_probe(struct platform_device *pdev)
 {
 	struct apple_spmi *spmi;
 	struct spmi_controller *ctrl;
+	int irq;
 	int ret;
 
 	ctrl = devm_spmi_controller_alloc(&pdev->dev, sizeof(*spmi));
@@ -195,6 +277,7 @@ static int apple_spmi_probe(struct platform_device *pdev)
 
 	spmi = spmi_controller_get_drvdata(ctrl);
 	mutex_init(&spmi->fifo_lock);
+	init_completion(&spmi->fifo_rx);
 
 	spmi->regs = devm_platform_ioremap_resource(pdev, 0);
 	if (IS_ERR(spmi->regs))
@@ -206,11 +289,23 @@ static int apple_spmi_probe(struct platform_device *pdev)
 	ctrl->write_cmd = spmi_write_cmd;
 	ctrl->cmd = spmi_cmd;
 
+	irq = platform_get_irq_optional(pdev, 0);
+	if (irq < 0 && irq != -ENXIO)
+		return irq;
+	if (irq >= 0) {
+		ret = apple_spmi_init_irq(pdev, spmi, irq);
+		if (ret)
+			return ret;
+	}
+
 	ret = devm_spmi_controller_add(&pdev->dev, ctrl);
 	if (ret)
 		return dev_err_probe(&pdev->dev, ret,
 				     "spmi_controller_add failed\n");
 
+	dev_dbg(&pdev->dev, irq >= 0 ? "Initialized with IRQ" :
+			"Initialized without IRQ, falling back to polling");
+
 	return 0;
 }
 

-- 
2.55.0