spi: core: add spi_split_transfers_maxsize

Add spi_split_transfers_maxsize method that splits
spi_transfers transparently into multiple transfers
that are below the given max-size.

This makes use of the spi_res framework via
spi_replace_transfers to allocate/free the extra
transfers as well as reverting back the changes applied
while processing the spi_message.

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

diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c
index 2ec8e66..34e3741 100644 (file)
--- a/drivers/spi/spi.c
+++ b/drivers/spi/spi.c
@@ -144,6 +144,8 @@ SPI_STATISTICS_TRANSFER_BYTES_HISTO(14, "16384-32767");
 SPI_STATISTICS_TRANSFER_BYTES_HISTO(15, "32768-65535");
 SPI_STATISTICS_TRANSFER_BYTES_HISTO(16, "65536+");
 
+SPI_STATISTICS_SHOW(transfers_split_maxsize, "%lu");
+
 static struct attribute *spi_dev_attrs[] = {
        &dev_attr_modalias.attr,
        NULL,
@@ -181,6 +183,7 @@ static struct attribute *spi_device_statistics_attrs[] = {
        &dev_attr_spi_device_transfer_bytes_histo14.attr,
        &dev_attr_spi_device_transfer_bytes_histo15.attr,
        &dev_attr_spi_device_transfer_bytes_histo16.attr,
+       &dev_attr_spi_device_transfers_split_maxsize.attr,
        NULL,
 };
 
@@ -223,6 +226,7 @@ static struct attribute *spi_master_statistics_attrs[] = {
        &dev_attr_spi_master_transfer_bytes_histo14.attr,
        &dev_attr_spi_master_transfer_bytes_histo15.attr,
        &dev_attr_spi_master_transfer_bytes_histo16.attr,
+       &dev_attr_spi_master_transfers_split_maxsize.attr,
        NULL,
 };
 
@@ -2237,6 +2241,113 @@ struct spi_replaced_transfers *spi_replace_transfers(
 }
 EXPORT_SYMBOL_GPL(spi_replace_transfers);
 
+int __spi_split_transfer_maxsize(struct spi_master *master,
+                                struct spi_message *msg,
+                                struct spi_transfer **xferp,
+                                size_t maxsize,
+                                gfp_t gfp)
+{
+       struct spi_transfer *xfer = *xferp, *xfers;
+       struct spi_replaced_transfers *srt;
+       size_t offset;
+       size_t count, i;
+
+       /* warn once about this fact that we are splitting a transfer */
+       dev_warn_once(&msg->spi->dev,
+                     "spi_transfer of length %i exceed max length of %i - needed to split transfers\n",
+                     xfer->len, maxsize);
+
+       /* calculate how many we have to replace */
+       count = DIV_ROUND_UP(xfer->len, maxsize);
+
+       /* create replacement */
+       srt = spi_replace_transfers(msg, xfer, 1, count, NULL, 0, gfp);
+       if (!srt)
+               return -ENOMEM;
+       xfers = srt->inserted_transfers;
+
+       /* now handle each of those newly inserted spi_transfers
+        * note that the replacements spi_transfers all are preset
+        * to the same values as *xferp, so tx_buf, rx_buf and len
+        * are all identical (as well as most others)
+        * so we just have to fix up len and the pointers.
+        *
+        * this also includes support for the depreciated
+        * spi_message.is_dma_mapped interface
+        */
+
+       /* the first transfer just needs the length modified, so we
+        * run it outside the loop
+        */
+       xfers[0].len = min(maxsize, xfer[0].len);
+
+       /* all the others need rx_buf/tx_buf also set */
+       for (i = 1, offset = maxsize; i < count; offset += maxsize, i++) {
+               /* update rx_buf, tx_buf and dma */
+               if (xfers[i].rx_buf)
+                       xfers[i].rx_buf += offset;
+               if (xfers[i].rx_dma)
+                       xfers[i].rx_dma += offset;
+               if (xfers[i].tx_buf)
+                       xfers[i].tx_buf += offset;
+               if (xfers[i].tx_dma)
+                       xfers[i].tx_dma += offset;
+
+               /* update length */
+               xfers[i].len = min(maxsize, xfers[i].len - offset);
+       }
+
+       /* we set up xferp to the last entry we have inserted,
+        * so that we skip those already split transfers
+        */
+       *xferp = &xfers[count - 1];
+
+       /* increment statistics counters */
+       SPI_STATISTICS_INCREMENT_FIELD(&master->statistics,
+                                      transfers_split_maxsize);
+       SPI_STATISTICS_INCREMENT_FIELD(&msg->spi->statistics,
+                                      transfers_split_maxsize);
+
+       return 0;
+}
+
+/**
+ * spi_split_tranfers_maxsize - split spi transfers into multiple transfers
+ *                              when an individual transfer exceeds a
+ *                              certain size
+ * @master:    the @spi_master for this transfer
+ * @message:   the @spi_message to transform
+ * @max_size:  the maximum when to apply this
+ *
+ * Return: status of transformation
+ */
+int spi_split_transfers_maxsize(struct spi_master *master,
+                               struct spi_message *msg,
+                               size_t maxsize,
+                               gfp_t gfp)
+{
+       struct spi_transfer *xfer;
+       int ret;
+
+       /* iterate over the transfer_list,
+        * but note that xfer is advanced to the last transfer inserted
+        * to avoid checking sizes again unnecessarily (also xfer does
+        * potentiall belong to a different list by the time the
+        * replacement has happened
+        */
+       list_for_each_entry(xfer, &msg->transfers, transfer_list) {
+               if (xfer->len > maxsize) {
+                       ret = __spi_split_transfer_maxsize(
+                               master, msg, &xfer, maxsize, gfp);
+                       if (ret)
+                               return ret;
+               }
+       }
+
+       return 0;
+}
+EXPORT_SYMBOL_GPL(spi_split_transfers_maxsize);
+
 /*-------------------------------------------------------------------------*/
 
 /* Core methods for SPI master protocol drivers.  Some of the

diff --git a/include/linux/spi/spi.h b/include/linux/spi/spi.h
index d713857..3c02b4d 100644 (file)
--- a/include/linux/spi/spi.h
+++ b/include/linux/spi/spi.h
@@ -53,6 +53,10 @@ extern struct bus_type spi_bus_type;
  *
  * @transfer_bytes_histo:
  *                 transfer bytes histogramm
+ *
+ * @transfers_split_maxsize:
+ *                 number of transfers that have been split because of
+ *                 maxsize limit
  */
 struct spi_statistics {
        spinlock_t              lock; /* lock for the whole structure */
@@ -72,6 +76,8 @@ struct spi_statistics {
 
 #define SPI_STATISTICS_HISTO_SIZE 17
        unsigned long transfer_bytes_histo[SPI_STATISTICS_HISTO_SIZE];
+
+       unsigned long transfers_split_maxsize;
 };
 
 void spi_statistics_add_transfer_stats(struct spi_statistics *stats,
@@ -935,6 +941,15 @@ extern struct spi_replaced_transfers *spi_replace_transfers(
 
 /*---------------------------------------------------------------------------*/
 
+/* SPI transfer transformation methods */
+
+extern int spi_split_transfers_maxsize(struct spi_master *master,
+                                      struct spi_message *msg,
+                                      size_t maxsize,
+                                      gfp_t gfp);
+
+/*---------------------------------------------------------------------------*/
+
 /* All these synchronous SPI transfer routines are utilities layered
  * over the core async transfer primitive.  Here, "synchronous" means
  * they will sleep uninterruptibly until the async transfer completes.