[PATCH v17 2/6] spi: pxa2xx: introduce clock enable and disable helper functions

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

The driver enables and disables the SOC clock during probe, teardown,
and power management callbacks. Directly calling clk_disable_unprepare()
when the clock is already disabled—such as when removing a device that
is runtime-suspended—causes an unbalanced clock disable warning from the
Common Clock Framework.

Introduce pxa2xx_spi_clk_enable() and pxa2xx_spi_clk_disable() helper
functions that track the clock state with a 'clk_enabled' boolean flag
protected by a 'clk_lock' mutex in struct driver_data. These helpers
make clock toggling idempotent: repeated enable or disable invocations
are safe no-ops serialized by clk_lock.

Convert probe, remove, suspend, resume, and runtime PM callbacks to use
these helpers instead of direct clk_prepare_enable() and
clk_disable_unprepare() calls.

Pack 'clk_enabled' immediately after 'n_bytes' into the existing
padding hole in struct driver_data, avoiding additional alignment
padding.

Assisted-by: Antigravity:gemini-3.8-flash sparse
Signed-off-by: Shih-Yuan Lee <fourdollars@debian.org>
---
 drivers/spi/spi-pxa2xx.c | 41 ++++++++++++++++++++++++++++++++--------
 drivers/spi/spi-pxa2xx.h |  2 ++
 2 files changed, 35 insertions(+), 8 deletions(-)

diff --git a/drivers/spi/spi-pxa2xx.c b/drivers/spi/spi-pxa2xx.c
index b11e30589074..a9d19d9a5343 100644
--- a/drivers/spi/spi-pxa2xx.c
+++ b/drivers/spi/spi-pxa2xx.c
@@ -713,6 +713,31 @@ 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 ret = 0;
+
+	mutex_lock(&drv_data->clk_lock);
+	if (!drv_data->clk_enabled) {
+		ret = clk_prepare_enable(drv_data->ssp->clk);
+		if (!ret)
+			drv_data->clk_enabled = true;
+	}
+	mutex_unlock(&drv_data->clk_lock);
+
+	return ret;
+}
+
+static void pxa2xx_spi_clk_disable(struct driver_data *drv_data)
+{
+	mutex_lock(&drv_data->clk_lock);
+	if (drv_data->clk_enabled) {
+		drv_data->clk_enabled = false;
+		clk_disable_unprepare(drv_data->ssp->clk);
+	}
+	mutex_unlock(&drv_data->clk_lock);
+}
+
 static irqreturn_t ssp_int(int irq, void *dev_id)
 {
 	struct driver_data *drv_data = dev_id;
@@ -1288,6 +1313,7 @@ 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;
+	mutex_init(&drv_data->clk_lock);
 
 	/* The spi->mode bits understood by this driver: */
 	controller->mode_bits = SPI_CPOL | SPI_CPHA | SPI_CS_HIGH | SPI_LOOP;
@@ -1352,7 +1378,7 @@ int pxa2xx_spi_probe(struct device *dev, struct ssp_device *ssp,
 	}
 
 	/* Enable SOC clock */
-	ret = clk_prepare_enable(ssp->clk);
+	ret = pxa2xx_spi_clk_enable(drv_data);
 	if (ret)
 		goto out_error_dma_irq_alloc;
 
@@ -1449,7 +1475,7 @@ int pxa2xx_spi_probe(struct device *dev, struct ssp_device *ssp,
 	return ret;
 
 out_error_clock_enabled:
-	clk_disable_unprepare(ssp->clk);
+	pxa2xx_spi_clk_disable(drv_data);
 
 out_error_dma_irq_alloc:
 	pxa2xx_spi_dma_release(drv_data);
@@ -1468,7 +1494,7 @@ void pxa2xx_spi_remove(struct device *dev)
 
 	/* Disable the SSP at the peripheral and SOC level */
 	pxa_ssp_disable(ssp);
-	clk_disable_unprepare(ssp->clk);
+	pxa2xx_spi_clk_disable(drv_data);
 
 	/* Release DMA */
 	if (drv_data->controller_info->enable_dma)
@@ -1492,7 +1518,7 @@ static int pxa2xx_spi_suspend(struct device *dev)
 	pxa_ssp_disable(ssp);
 
 	if (!pm_runtime_suspended(dev))
-		clk_disable_unprepare(ssp->clk);
+		pxa2xx_spi_clk_disable(drv_data);
 
 	return 0;
 }
@@ -1500,12 +1526,11 @@ static int pxa2xx_spi_suspend(struct device *dev)
 static int pxa2xx_spi_resume(struct device *dev)
 {
 	struct driver_data *drv_data = dev_get_drvdata(dev);
-	struct ssp_device *ssp = drv_data->ssp;
 	int ret;
 
 	/* Enable the SSP clock */
 	if (!pm_runtime_suspended(dev)) {
-		ret = clk_prepare_enable(ssp->clk);
+		ret = pxa2xx_spi_clk_enable(drv_data);
 		if (ret)
 			return ret;
 	}
@@ -1518,7 +1543,7 @@ 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);
+	pxa2xx_spi_clk_disable(drv_data);
 	return 0;
 }
 
@@ -1526,7 +1551,7 @@ static int pxa2xx_spi_runtime_resume(struct device *dev)
 {
 	struct driver_data *drv_data = dev_get_drvdata(dev);
 
-	return clk_prepare_enable(drv_data->ssp->clk);
+	return pxa2xx_spi_clk_enable(drv_data);
 }
 
 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..3352239f74a0 100644
--- a/drivers/spi/spi-pxa2xx.h
+++ b/drivers/spi/spi-pxa2xx.h
@@ -66,6 +66,8 @@ struct driver_data {
 	void *rx;
 	void *rx_end;
 	u8 n_bytes;
+	bool clk_enabled;
+	struct mutex clk_lock;
 	int (*write)(struct driver_data *drv_data);
 	int (*read)(struct driver_data *drv_data);
 	irqreturn_t (*transfer_handler)(struct driver_data *drv_data);
-- 
2.39.5