[PATCH v14 2/3] spi: pxa2xx: fix runtime PM and interrupt handling in PIO mode

[Shih-Yuan Lee <fourdollars@debian.org>]

When operating in PIO mode on Intel LPSS SPI controllers, runtime PM
autosuspend clock-gates the hardware block, causing PCIe Completion
Timeouts on subsequent MMIO accesses.

To fix this:
- Scope PIO mode autosuspend lockout (pm_runtime_get_noresume() /
  put_sync()) strictly to LPSS controllers via is_lpss_ssp(), preserving
  autosuspend for non-LPSS SoCs.
- Acquire pm_runtime_get_noresume() exactly once in pxa2xx_spi_probe()
  after spi_register_controller() succeeds, and release it via
  pm_runtime_put_sync() in pxa2xx_spi_remove(). Using pm_runtime_put_sync()
  ensures the runtime PM state machine transitions to RPM_SUSPENDED upon
  driver unbind, preventing active child count leaks on the parent LPSS
  power domain.
- Track clock state using drv_data->clk_enabled in helper functions
  pxa2xx_spi_clk_enable/disable() to prevent clock count underflows
  on error paths.
- Protect ssp_int() using drv_data->clk_enabled and drv_data->suspended
  flags to return IRQ_NONE immediately if the device is suspended or
  unclocked, avoiding unclocked MMIO reads and level-triggered shared IRQ
  storms. Active SPI transfers hold a PM reference via the SPI core,
  preventing autosuspend during FIFO transfers.
- Register IRQ in probe only after enabling the clock and clearing
  suspended.
- Overhaul teardown sequence in pxa2xx_spi_remove(), suspend, and
  runtime_suspend: first disable SSP hardware IRQ generation via
  pxa_ssp_disable(), set suspended flag, synchronize IRQ to drain in-flight
  handlers, and then disable clocks.
- Guard MMIO access in pxa2xx_spi_runtime_suspend() with
  drv_data->clk_enabled check.

Link: https://bugzilla.kernel.org/show_bug.cgi?id=108331
Signed-off-by: Shih-Yuan Lee <fourdollars@debian.org>
---
 drivers/spi/spi-pxa2xx.c | 138 +++++++++++++++++++++++++++++----------
 drivers/spi/spi-pxa2xx.h |   3 +
 2 files changed, 108 insertions(+), 33 deletions(-)

diff --git a/drivers/spi/spi-pxa2xx.c b/drivers/spi/spi-pxa2xx.c
index 6291d7c2e06f..443800bffbeb 100644
--- a/drivers/spi/spi-pxa2xx.c
+++ b/drivers/spi/spi-pxa2xx.c
@@ -72,7 +72,12 @@ struct chip_data {
 #define LPSS_CAPS_CS_EN_SHIFT			9
 #define LPSS_CAPS_CS_EN_MASK			(0xf << LPSS_CAPS_CS_EN_SHIFT)
 
-#define LPSS_PRIV_CLOCK_GATE 0x38
+/* Offsets from drv_data->lpss_base */
+#define LPSS_PRIV_RESETS			0x04
+#define LPSS_PRIV_RESETS_IDMA			BIT(2)
+#define LPSS_PRIV_RESETS_FUNC			0x3
+
+#define LPSS_PRIV_CLOCK_GATE			0x38
 #define LPSS_PRIV_CLOCK_GATE_CLK_CTL_MASK	0x3
 #define LPSS_PRIV_CLOCK_GATE_CLK_CTL_FORCE_ON	0x3
 #define LPSS_PRIV_CLOCK_GATE_CLK_CTL_FORCE_OFF	0x0
@@ -713,6 +718,28 @@ static void handle_bad_msg(struct driver_data *drv_data)
 	dev_err(drv_data->ssp->dev, "bad message state in interrupt handler\n");
 }
 
+static int pxa2xx_spi_clk_enable(struct driver_data *drv_data)
+{
+	int status;
+
+	if (drv_data->clk_enabled)
+		return 0;
+
+	status = clk_prepare_enable(drv_data->ssp->clk);
+	if (status == 0)
+		drv_data->clk_enabled = true;
+
+	return status;
+}
+
+static void pxa2xx_spi_clk_disable(struct driver_data *drv_data)
+{
+	if (drv_data->clk_enabled) {
+		clk_disable_unprepare(drv_data->ssp->clk);
+		drv_data->clk_enabled = false;
+	}
+}
+
 static irqreturn_t ssp_int(int irq, void *dev_id)
 {
 	struct driver_data *drv_data = dev_id;
@@ -721,19 +748,18 @@ static irqreturn_t ssp_int(int irq, void *dev_id)
 	u32 status;
 
 	/*
-	 * The IRQ might be shared with other peripherals so we must first
-	 * check that are we RPM suspended or not. If we are we assume that
-	 * the IRQ was not for us (we shouldn't be RPM suspended when the
-	 * interrupt is enabled).
+	 * The IRQ might be shared with other peripherals or trigger during
+	 * power state transitions. First check if device is suspended or if
+	 * clock is disabled; if so, return IRQ_NONE immediately to avoid
+	 * unclocked MMIO reads.
 	 */
-	if (pm_runtime_suspended(drv_data->ssp->dev))
+	if (drv_data->suspended || !drv_data->clk_enabled)
 		return IRQ_NONE;
 
 	/*
-	 * If the device is not yet in RPM suspended state and we get an
-	 * interrupt that is meant for another device, check if status bits
-	 * are all set to one. That means that the device is already
-	 * powered off.
+	 * If the device is not yet suspended and we get an interrupt that is
+	 * meant for another device, check if status bits are all set to one.
+	 * That means that the device is already powered off.
 	 */
 	status = pxa2xx_spi_read(drv_data, SSSR);
 	if (status == ~0)
@@ -1288,6 +1314,7 @@ int pxa2xx_spi_probe(struct device *dev, struct ssp_device *ssp,
 	drv_data->controller = controller;
 	drv_data->controller_info = platform_info;
 	drv_data->ssp = ssp;
+	drv_data->suspended = true; /* Start suspended until clock is enabled */
 
 	/* The spi->mode bits understood by this driver: */
 	controller->mode_bits = SPI_CPOL | SPI_CPHA | SPI_CS_HIGH | SPI_LOOP;
@@ -1330,10 +1357,6 @@ int pxa2xx_spi_probe(struct device *dev, struct ssp_device *ssp,
 						| SSSR_ROR | SSSR_TUR;
 	}
 
-	status = request_irq(ssp->irq, ssp_int, IRQF_SHARED, dev_name(dev),
-			drv_data);
-	if (status < 0)
-		return dev_err_probe(dev, status, "cannot get IRQ %d\n", ssp->irq);
 
 	/* Setup DMA if requested */
 	if (platform_info->enable_dma) {
@@ -1352,9 +1375,18 @@ int pxa2xx_spi_probe(struct device *dev, struct ssp_device *ssp,
 	}
 
 	/* Enable SOC clock */
-	status = clk_prepare_enable(ssp->clk);
+	status = pxa2xx_spi_clk_enable(drv_data);
 	if (status)
-		goto out_error_dma_irq_alloc;
+		goto out_error_dma_alloc;
+
+	drv_data->suspended = false;
+
+	status = request_irq(ssp->irq, ssp_int, IRQF_SHARED, dev_name(dev),
+			drv_data);
+	if (status < 0) {
+		status = dev_err_probe(dev, status, "cannot get IRQ %d\n", ssp->irq);
+		goto out_error_clock_enabled;
+	}
 
 	controller->max_speed_hz = clk_get_rate(ssp->clk);
 	/*
@@ -1434,7 +1466,7 @@ int pxa2xx_spi_probe(struct device *dev, struct ssp_device *ssp,
 						"ready", GPIOD_OUT_LOW);
 		if (IS_ERR(drv_data->gpiod_ready)) {
 			status = PTR_ERR(drv_data->gpiod_ready);
-			goto out_error_clock_enabled;
+			goto out_error_irq_alloc;
 		}
 	}
 
@@ -1443,17 +1475,22 @@ int pxa2xx_spi_probe(struct device *dev, struct ssp_device *ssp,
 	status = spi_register_controller(controller);
 	if (status) {
 		dev_err_probe(dev, status, "problem registering SPI controller\n");
-		goto out_error_clock_enabled;
+		goto out_error_irq_alloc;
 	}
 
+	if (is_lpss_ssp(drv_data) && !platform_info->enable_dma)
+		pm_runtime_get_noresume(dev);
+
 	return status;
 
+out_error_irq_alloc:
+	free_irq(ssp->irq, drv_data);
+
 out_error_clock_enabled:
-	clk_disable_unprepare(ssp->clk);
+	pxa2xx_spi_clk_disable(drv_data);
 
-out_error_dma_irq_alloc:
+out_error_dma_alloc:
 	pxa2xx_spi_dma_release(drv_data);
-	free_irq(ssp->irq, drv_data);
 
 	return status;
 }
@@ -1466,16 +1503,26 @@ void pxa2xx_spi_remove(struct device *dev)
 
 	spi_unregister_controller(drv_data->controller);
 
-	/* Disable the SSP at the peripheral and SOC level */
+	/* Disable SSP interrupt generation on hardware level while clock is active */
 	pxa_ssp_disable(ssp);
-	clk_disable_unprepare(ssp->clk);
 
-	/* Release DMA */
-	if (drv_data->controller_info->enable_dma)
-		pxa2xx_spi_dma_release(drv_data);
+	/* Mark as suspended to prevent further IRQ handling */
+	drv_data->suspended = true;
+
+	/* Wait for any pending interrupt handlers to complete */
+	synchronize_irq(ssp->irq);
 
 	/* Release IRQ */
 	free_irq(ssp->irq, drv_data);
+
+	/* Safe to disable the SSP clock now */
+	pxa2xx_spi_clk_disable(drv_data);
+
+	/* Release DMA */
+	if (drv_data->controller_info->enable_dma)
+		pxa2xx_spi_dma_release(drv_data);
+	else if (is_lpss_ssp(drv_data))
+		pm_runtime_put_sync(dev);
 }
 EXPORT_SYMBOL_NS_GPL(pxa2xx_spi_remove, "SPI_PXA2xx");
 
@@ -1490,10 +1537,10 @@ static int pxa2xx_spi_suspend(struct device *dev)
 		return status;
 
 	pxa_ssp_disable(ssp);
+	drv_data->suspended = true;
+	synchronize_irq(ssp->irq);
 
-	if (!pm_runtime_suspended(dev))
-		clk_disable_unprepare(ssp->clk);
-
+	pxa2xx_spi_clk_disable(drv_data);
 	return 0;
 }
 
@@ -1505,28 +1552,53 @@ static int pxa2xx_spi_resume(struct device *dev)
 
 	/* Enable the SSP clock */
 	if (!pm_runtime_suspended(dev)) {
-		status = clk_prepare_enable(ssp->clk);
+		status = pxa2xx_spi_clk_enable(drv_data);
 		if (status)
 			return status;
 	}
 
+	if (is_lpss_ssp(drv_data))
+		lpss_ssp_setup(drv_data);
+
+	drv_data->suspended = false;
+
 	/* Start the queue running */
-	return spi_controller_resume(drv_data->controller);
+	status = spi_controller_resume(drv_data->controller);
+	if (status) {
+		drv_data->suspended = true;
+		synchronize_irq(ssp->irq);
+		pxa2xx_spi_clk_disable(drv_data);
+		return status;
+	}
+
+	return 0;
 }
 
 static int pxa2xx_spi_runtime_suspend(struct device *dev)
 {
 	struct driver_data *drv_data = dev_get_drvdata(dev);
 
-	clk_disable_unprepare(drv_data->ssp->clk);
+	if (!drv_data->clk_enabled)
+		return 0;
+
+	pxa_ssp_disable(drv_data->ssp);
+	drv_data->suspended = true;
+	synchronize_irq(drv_data->ssp->irq);
+	pxa2xx_spi_clk_disable(drv_data);
 	return 0;
 }
 
 static int pxa2xx_spi_runtime_resume(struct device *dev)
 {
 	struct driver_data *drv_data = dev_get_drvdata(dev);
+	int status;
+
+	status = pxa2xx_spi_clk_enable(drv_data);
+	if (status)
+		return status;
 
-	return clk_prepare_enable(drv_data->ssp->clk);
+	drv_data->suspended = false;
+	return 0;
 }
 
 EXPORT_NS_GPL_DEV_PM_OPS(pxa2xx_spi_pm_ops, SPI_PXA2xx) = {
diff --git a/drivers/spi/spi-pxa2xx.h b/drivers/spi/spi-pxa2xx.h
index 447be0369384..44f37bf9c519 100644
--- a/drivers/spi/spi-pxa2xx.h
+++ b/drivers/spi/spi-pxa2xx.h
@@ -72,6 +72,9 @@ struct driver_data {
 
 	void __iomem *lpss_base;
 
+	bool suspended;
+	bool clk_enabled;
+
 	/* Optional slave FIFO ready signal */
 	struct gpio_desc *gpiod_ready;
 };
-- 
2.39.5