[PATCH v2 1/2] spi: Split spi message into chunks of <65535 in the spi subsystem

[Meghana Madhyastha <meghana.madhyastha@gmail.com>]

Split spi messages into chunks of <65535 in the spi subsystem and remove the message
length warning in bcm2835_spi_can_dma. This is so that the messages can be transferred
via dma and that the tinydrm drivers need not split it.

Signed-off-by: Meghana Madhyastha <meghana.madhyastha@gmail.com>
---
 drivers/spi/spi-bcm2835.c | 13 -------------
 drivers/spi/spi.c         |  8 ++++++++
 2 files changed, 8 insertions(+), 13 deletions(-)

diff --git a/drivers/spi/spi-bcm2835.c b/drivers/spi/spi-bcm2835.c
index f35cc10772f6..0dcc45f158b8 100644
--- a/drivers/spi/spi-bcm2835.c
+++ b/drivers/spi/spi-bcm2835.c
@@ -365,19 +365,6 @@ static bool bcm2835_spi_can_dma(struct spi_master *master,
 	if (tfr->len < BCM2835_SPI_DMA_MIN_LENGTH)
 		return false;
 
-	/* BCM2835_SPI_DLEN has defined a max transfer size as
-	 * 16 bit, so max is 65535
-	 * we can revisit this by using an alternative transfer
-	 * method - ideally this would get done without any more
-	 * interaction...
-	 */
-	if (tfr->len > 65535) {
-		dev_warn_once(&spi->dev,
-			      "transfer size of %d too big for dma-transfer\n",
-			      tfr->len);
-		return false;
-	}
-
 	/* if we run rx/tx_buf with word aligned addresses then we are OK */
 	if ((((size_t)tfr->rx_buf & 3) == 0) &&
 	    (((size_t)tfr->tx_buf & 3) == 0))
diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c
index b33a727a0158..e8e2c366a93b 100644
--- a/drivers/spi/spi.c
+++ b/drivers/spi/spi.c
@@ -1242,6 +1242,14 @@ static void __spi_pump_messages(struct spi_controller *ctlr, bool in_kthread)
 	trace_spi_message_start(ctlr->cur_msg);
 
 	if (ctlr->prepare_message) {
+		gfp_t gfp_flags = GFP_KERNEL | GFP_DMA;
+		size_t max_transfer_size = 32000;
+		ret = spi_split_transfers_maxsize(ctlr, ctlr->cur_msg, max_transfer_size, gfp_flags);
+		if (ret) {
+			dev_err(&ctlr->dev,
+				"failed to split message\n");
+			goto out;
+		}
 		ret = ctlr->prepare_message(ctlr, ctlr->cur_msg);
 		if (ret) {
 			dev_err(&ctlr->dev, "failed to prepare message: %d\n",
-- 
2.11.0

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