[PATCH 1/3] spi: bcm2835: add driver stats to debugfs

[kernel@xxxxxxxxxxxxxxxx]

From: Martin Sperl <kernel@xxxxxxxxxxxxxxxx>

To estimate efficiency add statistics on transfer types
(polling, interrupt and dma) used to debugfs.

Signed-off-by: Martin Sperl <kernel@xxxxxxxxxxxxxxxx>
---
 drivers/spi/spi-bcm2835.c | 68 +++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 68 insertions(+)

diff --git a/drivers/spi/spi-bcm2835.c b/drivers/spi/spi-bcm2835.c
index c2912c1e09c5..0ccc6a2733c6 100644
--- a/drivers/spi/spi-bcm2835.c
+++ b/drivers/spi/spi-bcm2835.c
@@ -22,6 +22,7 @@

 #include <linux/clk.h>
 #include <linux/completion.h>
+#include <linux/debugfs.h>
 #include <linux/delay.h>
 #include <linux/dma-mapping.h>
 #include <linux/dmaengine.h>
@@ -111,8 +112,60 @@ struct bcm2835_spi {
 	int rx_prologue;
 	unsigned int tx_spillover;
 	unsigned int dma_pending;
+
+#if defined(CONFIG_DEBUG_FS)
+#define BCM2835_AUX_INCR(field) ((field)++)
+	u64 count_transfer_polling;
+	u64 count_transfer_irq;
+	u64 count_transfer_irq_after_poll;
+	u64 count_transfer_dma;
+
+	struct dentry *debugfs_dir;
+#else
+#define BCM2835_AUX_INCR(field)
+#endif /* CONFIG_DEBUG_FS */
 };

+#if defined(CONFIG_DEBUG_FS)
+static void bcm2835_debugfs_create(struct bcm2835_spi *bs,
+				   const char *dname)
+{
+	char name[64];
+	struct dentry *dir;
+
+	/* get full name */
+	snprintf(name, sizeof(name), "spi-bcm2835-%s", dname);
+
+	/* the base directory */
+	dir = debugfs_create_dir(name, NULL);
+	bs->debugfs_dir = dir;
+
+	/* the counters */
+	debugfs_create_u64("count_transfer_polling", 0444, dir,
+			   &bs->count_transfer_polling);
+	debugfs_create_u64("count_transfer_irq", 0444, dir,
+			   &bs->count_transfer_irq);
+	debugfs_create_u64("count_transfer_irq_after_poll", 0444, dir,
+			   &bs->count_transfer_irq_after_poll);
+	debugfs_create_u64("count_transfer_dma", 0444, dir,
+			   &bs->count_transfer_dma);
+}
+
+static void bcm2835_debugfs_remove(struct bcm2835_spi *bs)
+{
+	debugfs_remove_recursive(bs->debugfs_dir);
+	bs->debugfs_dir = NULL;
+}
+#else
+static void bcm2835_debugfs_create(struct bcm2835_spi *bs)
+{
+}
+
+static void bcm2835_debugfs_remove(struct bcm2835_spi *bs)
+{
+}
+#endif /* CONFIG_DEBUG_FS */
+
 static inline u32 bcm2835_rd(struct bcm2835_spi *bs, unsigned reg)
 {
 	return readl(bs->regs + reg);
@@ -316,6 +369,9 @@ static int bcm2835_spi_transfer_one_irq(struct spi_master *master,
 {
 	struct bcm2835_spi *bs = spi_master_get_devdata(master);

+	/* update statistics */
+	BCM2835_AUX_INCR(bs->count_transfer_irq);
+
 	/*
 	 * Enable HW block, but with interrupts still disabled.
 	 * Otherwise the empty TX FIFO would immediately trigger an interrupt.
@@ -574,6 +630,9 @@ static int bcm2835_spi_transfer_one_dma(struct spi_master *master,
 	struct bcm2835_spi *bs = spi_master_get_devdata(master);
 	int ret;

+	/* update statistics */
+	BCM2835_AUX_INCR(bs->count_transfer_dma);
+
 	/*
 	 * Transfer first few bytes without DMA if length of first TX or RX
 	 * sglist entry is not a multiple of 4 bytes (hardware limitation).
@@ -731,6 +790,9 @@ static int bcm2835_spi_transfer_one_poll(struct spi_master *master,
 	struct bcm2835_spi *bs = spi_master_get_devdata(master);
 	unsigned long timeout;

+	/* update statistics */
+	BCM2835_AUX_INCR(bs->count_transfer_polling);
+
 	/* enable HW block without interrupts */
 	bcm2835_wr(bs, BCM2835_SPI_CS, cs | BCM2835_SPI_CS_TA);

@@ -759,6 +821,8 @@ static int bcm2835_spi_transfer_one_poll(struct spi_master *master,
 					    "timeout period reached: jiffies: %lu remaining tx/rx: %d/%d - falling back to interrupt mode\n",
 					    jiffies - timeout,
 					    bs->tx_len, bs->rx_len);
+			/* update statistics */
+			BCM2835_AUX_INCR(bs->count_transfer_irq_after_poll);
 			/* fall back to interrupt mode */
 			return bcm2835_spi_transfer_one_irq(master, spi,
 							    tfr, cs, false);
@@ -991,6 +1055,8 @@ static int bcm2835_spi_probe(struct platform_device *pdev)
 		goto out_clk_disable;
 	}

+	bcm2835_debugfs_create(bs, dev_name(&pdev->dev));
+
 	return 0;

 out_clk_disable:
@@ -1005,6 +1071,8 @@ static int bcm2835_spi_remove(struct platform_device *pdev)
 	struct spi_master *master = platform_get_drvdata(pdev);
 	struct bcm2835_spi *bs = spi_master_get_devdata(master);

+	bcm2835_debugfs_remove(bs);
+
 	/* Clear FIFOs, and disable the HW block */
 	bcm2835_wr(bs, BCM2835_SPI_CS,
 		   BCM2835_SPI_CS_CLEAR_RX | BCM2835_SPI_CS_CLEAR_TX);
--
2.11.0