From 0b2b66514fc9971b3a6002ba038d74f77705fd34 Mon Sep 17 00:00:00 2001 From: Serge Semin Date: Fri, 29 May 2020 16:11:56 +0300 Subject: spi: dw: Use DMA max burst to set the request thresholds Each channel of DMA controller may have a limited length of burst transaction (number of IO operations performed at ones in a single DMA client request). This parameter can be used to setup the most optimal DMA Tx/Rx data level values. In order to avoid the Tx buffer overrun we can set the DMA Tx level to be of FIFO depth minus the maximum burst transactions length. To prevent the Rx buffer underflow the DMA Rx level should be set to the maximum burst transactions length. This commit setups the DMA channels and the DW SPI DMA Tx/Rx levels in accordance with these rules. Signed-off-by: Serge Semin Reviewed-by: Andy Shevchenko Cc: Alexey Malahov Cc: Thomas Bogendoerfer Cc: Arnd Bergmann Cc: Feng Tang Cc: Rob Herring Cc: linux-mips@vger.kernel.org Cc: devicetree@vger.kernel.org Link: https://lore.kernel.org/r/20200529131205.31838-8-Sergey.Semin@baikalelectronics.ru Signed-off-by: Mark Brown --- drivers/spi/spi-dw.h | 2 ++ 1 file changed, 2 insertions(+) (limited to 'drivers/spi/spi-dw.h') diff --git a/drivers/spi/spi-dw.h b/drivers/spi/spi-dw.h index 9585d0c83a6d..9247670fcdfb 100644 --- a/drivers/spi/spi-dw.h +++ b/drivers/spi/spi-dw.h @@ -142,7 +142,9 @@ struct dw_spi { /* DMA info */ struct dma_chan *txchan; + u32 txburst; struct dma_chan *rxchan; + u32 rxburst; unsigned long dma_chan_busy; dma_addr_t dma_addr; /* phy address of the Data register */ const struct dw_spi_dma_ops *dma_ops; -- cgit v1.2.3