From 1224e29572f655facfcd850cf0f0a4784f36a903 Mon Sep 17 00:00:00 2001
From: Vincent Whitchurch <vincent.whitchurch@axis.com>
Date: Tue, 27 Sep 2022 13:21:17 +0200
Subject: [PATCH] spi: s3c64xx: Fix large transfers with DMA
Git-commit: 1224e29572f655facfcd850cf0f0a4784f36a903
Patch-mainline: v6.1-rc1
References: git-fixes

The COUNT_VALUE in the PACKET_CNT register is 16-bit so the maximum
value is 65535.  Asking the driver to transfer a larger size currently
leads to the DMA transfer timing out.  Implement ->max_transfer_size()
and have the core split the transfer as needed.

Fixes: 230d42d422e7 ("spi: Add s3c64xx SPI Controller driver")
Signed-off-by: Vincent Whitchurch <vincent.whitchurch@axis.com>
Link: https://lore.kernel.org/r/20220927112117.77599-5-vincent.whitchurch@axis.com
Signed-off-by: Mark Brown <broonie@kernel.org>
Acked-by: Takashi Iwai <tiwai@suse.de>

---
 drivers/spi/spi-s3c64xx.c |    9 +++++++++
 1 file changed, 9 insertions(+)

--- a/drivers/spi/spi-s3c64xx.c
+++ b/drivers/spi/spi-s3c64xx.c
@@ -85,6 +85,7 @@
 #define S3C64XX_SPI_ST_TX_FIFORDY		(1<<0)
 
 #define S3C64XX_SPI_PACKET_CNT_EN		(1<<16)
+#define S3C64XX_SPI_PACKET_CNT_MASK		GENMASK(15, 0)
 
 #define S3C64XX_SPI_PND_TX_UNDERRUN_CLR		(1<<4)
 #define S3C64XX_SPI_PND_TX_OVERRUN_CLR		(1<<3)
@@ -661,6 +662,13 @@ static int s3c64xx_spi_prepare_message(s
 	return 0;
 }
 
+static size_t s3c64xx_spi_max_transfer_size(struct spi_device *spi)
+{
+	struct spi_controller *ctlr = spi->controller;
+
+	return ctlr->can_dma ? S3C64XX_SPI_PACKET_CNT_MASK : SIZE_MAX;
+}
+
 static int s3c64xx_spi_transfer_one(struct spi_master *master,
 				    struct spi_device *spi,
 				    struct spi_transfer *xfer)
@@ -1130,6 +1138,7 @@ static int s3c64xx_spi_probe(struct plat
 	master->prepare_transfer_hardware = s3c64xx_spi_prepare_transfer;
 	master->prepare_message = s3c64xx_spi_prepare_message;
 	master->transfer_one = s3c64xx_spi_transfer_one;
+	master->max_transfer_size = s3c64xx_spi_max_transfer_size;
 	master->num_chipselect = sci->num_cs;
 	master->dma_alignment = 8;
 	master->bits_per_word_mask = SPI_BPW_MASK(32) | SPI_BPW_MASK(16) |