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 2ec8e66a..34e3741 100644
--- a/drivers/spi/spi.c
+++ b/drivers/spi/spi.c
@@ -144,6 +144,8 @@
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 @@
&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 @@
&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 @@
}
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