From f3530f26f8e9869e6e8c3370cf6f61330774fe2b Mon Sep 17 00:00:00 2001 From: Patrice Chotard Date: Mon, 19 Apr 2021 14:15:40 +0200 Subject: spi: stm32-qspi: Trigger DMA only if more than 4 bytes to transfer In order to optimize accesses to spi flashes, trigger a DMA only if more than 4 bytes has to be transferred. DMA transfer preparation's cost becomes negligible above 4 bytes to transfer. Below this threshold, indirect transfer give more throughput. mtd_speedtest shows that page write throughtput increases : - from 779 to 853 KiB/s (~9.5%) with s25fl512s SPI-NOR. - from 5283 to 5666 KiB/s (~7.25%) with Micron SPI-NAND. Signed-off-by: Christophe Kerello Signed-off-by: Patrice Chotard Link: https://lore.kernel.org/r/20210419121541.11617-3-patrice.chotard@foss.st.com Signed-off-by: Mark Brown --- drivers/spi/spi-stm32-qspi.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/drivers/spi/spi-stm32-qspi.c b/drivers/spi/spi-stm32-qspi.c index 2786470a5201..6e74d6bed54c 100644 --- a/drivers/spi/spi-stm32-qspi.c +++ b/drivers/spi/spi-stm32-qspi.c @@ -269,8 +269,9 @@ static int stm32_qspi_tx(struct stm32_qspi *qspi, const struct spi_mem_op *op) if (qspi->fmode == CCR_FMODE_MM) return stm32_qspi_tx_mm(qspi, op); - else if ((op->data.dir == SPI_MEM_DATA_IN && qspi->dma_chrx) || - (op->data.dir == SPI_MEM_DATA_OUT && qspi->dma_chtx)) + else if (((op->data.dir == SPI_MEM_DATA_IN && qspi->dma_chrx) || + (op->data.dir == SPI_MEM_DATA_OUT && qspi->dma_chtx)) && + op->data.nbytes > 4) if (!stm32_qspi_tx_dma(qspi, op)) return 0; -- cgit v1.2.3