spi: add transfer histogram statistics via sysfs

report transfer sizes as a histogram via the following files:
  /sys/class/spi_master/spi*/statistics/transfer_bytes_histo_*
  /sys/class/spi_master/spi*/spi*.*/statistics/transfer_bytes_histo_*

Signed-off-by: Martin Sperl <kernel@martin.sperl.org>
Signed-off-by: Mark Brown <broonie@kernel.org>

drivers/spi/spi.c

@@ -123,6 +123,28 @@ SPI_STATISTICS_SHOW(bytes, "%llu");
 SPI_STATISTICS_SHOW(bytes_rx, "%llu");
 SPI_STATISTICS_SHOW(bytes_tx, "%llu");
 
+#define SPI_STATISTICS_TRANSFER_BYTES_HISTO(index, number)		\
+	SPI_STATISTICS_SHOW_NAME(transfer_bytes_histo##index,		\
+				 "transfer_bytes_histo_" number,	\
+				 transfer_bytes_histo[index],  "%lu")
+SPI_STATISTICS_TRANSFER_BYTES_HISTO(0,  "0-1");
+SPI_STATISTICS_TRANSFER_BYTES_HISTO(1,  "2-3");
+SPI_STATISTICS_TRANSFER_BYTES_HISTO(2,  "4-7");
+SPI_STATISTICS_TRANSFER_BYTES_HISTO(3,  "8-15");
+SPI_STATISTICS_TRANSFER_BYTES_HISTO(4,  "16-31");
+SPI_STATISTICS_TRANSFER_BYTES_HISTO(5,  "32-63");
+SPI_STATISTICS_TRANSFER_BYTES_HISTO(6,  "64-127");
+SPI_STATISTICS_TRANSFER_BYTES_HISTO(7,  "128-255");
+SPI_STATISTICS_TRANSFER_BYTES_HISTO(8,  "256-511");
+SPI_STATISTICS_TRANSFER_BYTES_HISTO(9,  "512-1023");
+SPI_STATISTICS_TRANSFER_BYTES_HISTO(10, "1024-2047");
+SPI_STATISTICS_TRANSFER_BYTES_HISTO(11, "2048-4095");
+SPI_STATISTICS_TRANSFER_BYTES_HISTO(12, "4096-8191");
+SPI_STATISTICS_TRANSFER_BYTES_HISTO(13, "8192-16383");
+SPI_STATISTICS_TRANSFER_BYTES_HISTO(14, "16384-32767");
+SPI_STATISTICS_TRANSFER_BYTES_HISTO(15, "32768-65535");
+SPI_STATISTICS_TRANSFER_BYTES_HISTO(16, "65536+");
+
 static struct attribute *spi_dev_attrs[] = {
 	&dev_attr_modalias.attr,
 	NULL,
@@ -143,6 +165,23 @@ static struct attribute *spi_device_statistics_attrs[] = {
 	&dev_attr_spi_device_bytes.attr,
 	&dev_attr_spi_device_bytes_rx.attr,
 	&dev_attr_spi_device_bytes_tx.attr,
+	&dev_attr_spi_device_transfer_bytes_histo0.attr,
+	&dev_attr_spi_device_transfer_bytes_histo1.attr,
+	&dev_attr_spi_device_transfer_bytes_histo2.attr,
+	&dev_attr_spi_device_transfer_bytes_histo3.attr,
+	&dev_attr_spi_device_transfer_bytes_histo4.attr,
+	&dev_attr_spi_device_transfer_bytes_histo5.attr,
+	&dev_attr_spi_device_transfer_bytes_histo6.attr,
+	&dev_attr_spi_device_transfer_bytes_histo7.attr,
+	&dev_attr_spi_device_transfer_bytes_histo8.attr,
+	&dev_attr_spi_device_transfer_bytes_histo9.attr,
+	&dev_attr_spi_device_transfer_bytes_histo10.attr,
+	&dev_attr_spi_device_transfer_bytes_histo11.attr,
+	&dev_attr_spi_device_transfer_bytes_histo12.attr,
+	&dev_attr_spi_device_transfer_bytes_histo13.attr,
+	&dev_attr_spi_device_transfer_bytes_histo14.attr,
+	&dev_attr_spi_device_transfer_bytes_histo15.attr,
+	&dev_attr_spi_device_transfer_bytes_histo16.attr,
 	NULL,
 };
 
@@ -168,6 +207,23 @@ static struct attribute *spi_master_statistics_attrs[] = {
 	&dev_attr_spi_master_bytes.attr,
 	&dev_attr_spi_master_bytes_rx.attr,
 	&dev_attr_spi_master_bytes_tx.attr,
+	&dev_attr_spi_master_transfer_bytes_histo0.attr,
+	&dev_attr_spi_master_transfer_bytes_histo1.attr,
+	&dev_attr_spi_master_transfer_bytes_histo2.attr,
+	&dev_attr_spi_master_transfer_bytes_histo3.attr,
+	&dev_attr_spi_master_transfer_bytes_histo4.attr,
+	&dev_attr_spi_master_transfer_bytes_histo5.attr,
+	&dev_attr_spi_master_transfer_bytes_histo6.attr,
+	&dev_attr_spi_master_transfer_bytes_histo7.attr,
+	&dev_attr_spi_master_transfer_bytes_histo8.attr,
+	&dev_attr_spi_master_transfer_bytes_histo9.attr,
+	&dev_attr_spi_master_transfer_bytes_histo10.attr,
+	&dev_attr_spi_master_transfer_bytes_histo11.attr,
+	&dev_attr_spi_master_transfer_bytes_histo12.attr,
+	&dev_attr_spi_master_transfer_bytes_histo13.attr,
+	&dev_attr_spi_master_transfer_bytes_histo14.attr,
+	&dev_attr_spi_master_transfer_bytes_histo15.attr,
+	&dev_attr_spi_master_transfer_bytes_histo16.attr,
 	NULL,
 };
 
@@ -186,10 +242,15 @@ void spi_statistics_add_transfer_stats(struct spi_statistics *stats,
 				       struct spi_master *master)
 {
 	unsigned long flags;
+	int l2len = min(fls(xfer->len), SPI_STATISTICS_HISTO_SIZE) - 1;
+
+	if (l2len < 0)
+		l2len = 0;
 
 	spin_lock_irqsave(&stats->lock, flags);
 
 	stats->transfers++;
+	stats->transfer_bytes_histo[l2len]++;
 
 	stats->bytes += xfer->len;
 	if ((xfer->tx_buf) &&

include/linux/spi/spi.h

@@ -51,6 +51,8 @@ extern struct bus_type spi_bus_type;
  * @bytes_tx:      number of bytes sent to device
  * @bytes_rx:      number of bytes received from device
  *
+ * @transfer_bytes_histo:
+ *                 transfer bytes histogramm
  */
 struct spi_statistics {
 	spinlock_t		lock; /* lock for the whole structure */
@@ -68,6 +70,8 @@ struct spi_statistics {
 	unsigned long long	bytes_rx;
 	unsigned long long	bytes_tx;
 
+#define SPI_STATISTICS_HISTO_SIZE 17
+	unsigned long transfer_bytes_histo[SPI_STATISTICS_HISTO_SIZE];
 };
 
 void spi_statistics_add_transfer_stats(struct spi_statistics *stats,