spi: bcm2835: add driver stats to debugfs

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

Signed-off-by: Martin Sperl <kernel@martin.sperl.org>
Changelog:
  V1 -> V2: applied feedback by Stefan Wahren
            reorganized patchset
	    added extra rational, descriptions
	    fixed compile issue when CONFIG_DEBUG_FS is unset
Signed-off-by: Mark Brown <broonie@kernel.org>

diff --git a/drivers/spi/spi-bcm2835.c b/drivers/spi/spi-bcm2835.c
index 3230d37fa89a83d2e2091aaa11fe6b1ed484dd0a..eb67da697ef52c350d7c02a809d1f4e08c62e28a 100644 (file)
--- 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>
@@ -101,6 +102,15 @@ MODULE_PARM_DESC(polling_limit_us,
  *     length is not a multiple of 4 (to overcome hardware limitation)
  * @tx_spillover: whether @tx_prologue spills over to second TX sglist entry
  * @dma_pending: whether a DMA transfer is in progress
+ * @debugfs_dir: the debugfs directory - neede to remove debugfs when
+ *      unloading the module
+ * @count_transfer_polling: count of how often polling mode is used
+ * @count_transfer_irq: count of how often interrupt mode is used
+ * @count_transfer_irq_after_polling: count of how often we fall back to
+ *      interrupt mode after starting in polling mode.
+ *      These are counted as well in @count_transfer_polling and
+ *      @count_transfer_irq
+ * @count_transfer_dma: count how often dma mode is used
  */
 struct bcm2835_spi {
        void __iomem *regs;
@@ -115,8 +125,55 @@ struct bcm2835_spi {
        int rx_prologue;
        unsigned int tx_spillover;
        unsigned int dma_pending;
+
+       struct dentry *debugfs_dir;
+       u64 count_transfer_polling;
+       u64 count_transfer_irq;
+       u64 count_transfer_irq_after_polling;
+       u64 count_transfer_dma;
 };
 
+#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_polling", 0444, dir,
+                          &bs->count_transfer_irq_after_polling);
+       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,
+                                  const char *dname)
+{
+}
+
+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);
@@ -320,6 +377,9 @@ static int bcm2835_spi_transfer_one_irq(struct spi_master *master,
 {
        struct bcm2835_spi *bs = spi_master_get_devdata(master);
 
+       /* update usage statistics */
+       bs->count_transfer_irq++;
+
        /*
         * Enable HW block, but with interrupts still disabled.
         * Otherwise the empty TX FIFO would immediately trigger an interrupt.
@@ -564,6 +624,9 @@ static int bcm2835_spi_transfer_one_dma(struct spi_master *master,
        struct bcm2835_spi *bs = spi_master_get_devdata(master);
        int ret;
 
+       /* update usage statistics */
+       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).
@@ -706,6 +769,9 @@ static int bcm2835_spi_transfer_one_poll(struct spi_master *master,
        struct bcm2835_spi *bs = spi_master_get_devdata(master);
        unsigned long timeout;
 
+       /* update usage statistics */
+       bs->count_transfer_polling++;
+
        /* enable HW block without interrupts */
        bcm2835_wr(bs, BCM2835_SPI_CS, cs | BCM2835_SPI_CS_TA);
 
@@ -735,6 +801,10 @@ static int bcm2835_spi_transfer_one_poll(struct spi_master *master,
                                            jiffies - timeout,
                                            bs->tx_len, bs->rx_len);
                        /* fall back to interrupt mode */
+
+                       /* update usage statistics */
+                       bs->count_transfer_irq_after_polling++;
+
                        return bcm2835_spi_transfer_one_irq(master, spi,
                                                            tfr, cs, false);
                }
@@ -982,6 +1052,8 @@ 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:
@@ -996,6 +1068,8 @@ 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);