linux-kernel - [PATCH] spi: bcm2835: implement ctlr->max_transfer

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Date: Fri, 26 Jan 2024 16:00:23 -0600
From: David Lechner <dlechner@...libre.com>
To: Mark Brown <broonie@...nel.org>,
	Florian Fainelli <florian.fainelli@...adcom.com>,
	Ray Jui <rjui@...adcom.com>,
	Scott Branden <sbranden@...adcom.com>
Cc: David Lechner <dlechner@...libre.com>,
	Broadcom internal kernel review list <bcm-kernel-feedback-list@...adcom.com>,
	linux-spi@...r.kernel.org,
	linux-rpi-kernel@...ts.infradead.org,
	linux-arm-kernel@...ts.infradead.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH] spi: bcm2835: implement ctlr->max_transfer_size

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@...libre.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