[PATCH] spi: bcm2835: implement ctlr->max_transfer_size

[PATCH] spi: bcm2835: implement ctlr->max_transfer_size

[David Lechner]

The core SPI code will handle splitting transfers if needed as long
as ctlr->max_transfer_size is implemented. It does this in
__spi_pump_transfer_message() immediately before calling
ctlr->prepare_message. So effectively, this change does not
alter the behavior of the driver.

Also, several peripheral drivers make use of spi_max_transfer_size(),
so this should improve compatibility with those drivers.

Signed-off-by: David Lechner <dlechner@baylibre.com>
---
 drivers/spi/spi-bcm2835.c | 27 ++++++++++++++-------------
 1 file changed, 14 insertions(+), 13 deletions(-)

diff --git a/drivers/spi/spi-bcm2835.c b/drivers/spi/spi-bcm2835.c
index e709887eb2a9..e1b9b1235787 100644
--- a/drivers/spi/spi-bcm2835.c
+++ b/drivers/spi/spi-bcm2835.c
@@ -1117,19 +1117,6 @@ static int bcm2835_spi_prepare_message(struct spi_controller *ctlr,
 	struct spi_device *spi = msg->spi;
 	struct bcm2835_spi *bs = spi_controller_get_devdata(ctlr);
 	struct bcm2835_spidev *target = spi_get_ctldata(spi);
-	int ret;
-
-	if (ctlr->can_dma) {
-		/*
-		 * DMA transfers are limited to 16 bit (0 to 65535 bytes) by
-		 * the SPI HW due to DLEN. Split up transfers (32-bit FIFO
-		 * aligned) if the limit is exceeded.
-		 */
-		ret = spi_split_transfers_maxsize(ctlr, msg, 65532,
-						  GFP_KERNEL | GFP_DMA);
-		if (ret)
-			return ret;
-	}
 
 	/*
 	 * Set up clock polarity before spi_transfer_one_message() asserts
@@ -1219,6 +1206,19 @@ static int bcm2835_spi_setup_dma(struct spi_controller *ctlr,
 	return 0;
 }
 
+static size_t bcm2835_spi_max_transfer_size(struct spi_device *spi)
+{
+	/*
+	 * DMA transfers are limited to 16 bit (0 to 65535 bytes) by
+	 * the SPI HW due to DLEN. Split up transfers (32-bit FIFO
+	 * aligned) if the limit is exceeded.
+	 */
+	if (spi->controller->can_dma)
+		return 65532;
+
+	return SIZE_MAX;
+}
+
 static int bcm2835_spi_setup(struct spi_device *spi)
 {
 	struct spi_controller *ctlr = spi->controller;
@@ -1348,6 +1348,7 @@ static int bcm2835_spi_probe(struct platform_device *pdev)
 	ctlr->mode_bits = BCM2835_SPI_MODE_BITS;
 	ctlr->bits_per_word_mask = SPI_BPW_MASK(8);
 	ctlr->num_chipselect = 3;
+	ctlr->max_transfer_size = bcm2835_spi_max_transfer_size;
 	ctlr->setup = bcm2835_spi_setup;
 	ctlr->cleanup = bcm2835_spi_cleanup;
 	ctlr->transfer_one = bcm2835_spi_transfer_one;
-- 
2.43.0

Re: [PATCH] spi: bcm2835: implement ctlr->max_transfer_size

[Mark Brown]

On Fri, 26 Jan 2024 16:00:23 -0600, David Lechner wrote:
> The core SPI code will handle splitting transfers if needed as long
> as ctlr->max_transfer_size is implemented. It does this in
> __spi_pump_transfer_message() immediately before calling
> ctlr->prepare_message. So effectively, this change does not
> alter the behavior of the driver.
> 
> Also, several peripheral drivers make use of spi_max_transfer_size(),
> so this should improve compatibility with those drivers.
> 
> [...]

Applied to

   https://git.kernel.org/pub/scm/linux/kernel/git/broonie/spi.git for-next

Thanks!

[1/1] spi: bcm2835: implement ctlr->max_transfer_size
      commit: 2733092baa3e8a1f05fd16088808be17c98990b4

All being well this means that it will be integrated into the linux-next
tree (usually sometime in the next 24 hours) and sent to Linus during
the next merge window (or sooner if it is a bug fix), however if
problems are discovered then the patch may be dropped or reverted.

You may get further e-mails resulting from automated or manual testing
and review of the tree, please engage with people reporting problems and
send followup patches addressing any issues that are reported if needed.

If any updates are required or you are submitting further changes they
should be sent as incremental updates against current git, existing
patches will not be replaced.

Please add any relevant lists and maintainers to the CCs when replying
to this mail.

Thanks,
Mark