From 90ef2f2961c2dc55957dafe2f53b3efdb4675efc Mon Sep 17 00:00:00 2001 From: Vijaya Krishna Nivarthi Date: Wed, 22 Jul 2026 14:53:58 +0530 Subject: [PATCH] spi: qcom-qspi: Correct max DMA length to avoid 64K boundary failure The maximum size for a DMA data descriptor is 64KB-1 because the size field in HW is 16 bits wide. For this reason, transfers fail at 64KB and beyond. Lower max_dma_len to 60KB so larger transfers are split into multiple DMA blocks and do not hit the failing 64KB boundary. 60KB is chosen as a safe round number below the 64KB-1 hardware limit while satisfying alignment requirements. Tested on x1e80100 (Hamoa) with SPI-NOR flash (/dev/mtd0): Without patch: dd if=/dev/mtd0 of=/tmp/spi_dump.bin bs=32768 count=2 # works dd if=/dev/mtd0 of=/tmp/spi_dump.bin bs=65536 count=1 # fails With patch: dd if=/dev/mtd0 of=/tmp/spi_dump.bin bs=65536 count=1 # works Fixes: b5762d95607e ("spi: spi-qcom-qspi: Add DMA mode support") Cc: stable@vger.kernel.org Signed-off-by: Vijaya Krishna Nivarthi Link: https://patch.msgid.link/20260722092358.459943-1-vnivarth@qti.qualcomm.com Signed-off-by: Mark Brown --- drivers/spi/spi-qcom-qspi.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/drivers/spi/spi-qcom-qspi.c b/drivers/spi/spi-qcom-qspi.c index caf55a6f70b31..e9fdefa9d65dc 100644 --- a/drivers/spi/spi-qcom-qspi.c +++ b/drivers/spi/spi-qcom-qspi.c @@ -775,7 +775,8 @@ static int qcom_qspi_probe(struct platform_device *pdev) return dev_err_probe(dev, ret, "could not set DMA mask\n"); host->max_speed_hz = 300000000; - host->max_dma_len = 65536; /* as per HPG */ + /* as per HPG, it is 64KB, limit to 60KB to avoid boundary condition failures */ + host->max_dma_len = 0xf000; host->dma_alignment = QSPI_ALIGN_REQ; host->num_chipselect = QSPI_NUM_CS; host->bus_num = -1; -- 2.47.3