From 501943696ea4f4194705b7449547fd3d66c13e97 Mon Sep 17 00:00:00 2001 From: Axel Lin Date: Tue, 6 Jan 2015 08:08:25 +0800 Subject: [PATCH] spi: designware_spi: Fix detecting FIFO depth Current code tries to find the highest valid fifo depth by checking the value it wrote to DW_SPI_TXFLTR. There are a few problems in current code: 1) There is an off-by-one in dws->fifo_len setting because it assumes the latest register write fails so the latest valid value should be fifo - 1. 2) We know the depth could be from 2 to 256 from HW spec, so it is not necessary to test fifo == 257. In the case fifo is 257, it means the latest valid setting is fifo = 256. So after the for loop iteration, we should check fifo == 2 case instead of fifo == 257 if detecting the FIFO depth fails. This patch fixes above issues. Signed-off-by: Axel Lin Acked-by: Stefan Roese Reviewed-by: Jagannadha Sutradharudu Teki --- drivers/spi/designware_spi.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/drivers/spi/designware_spi.c b/drivers/spi/designware_spi.c index 98c9f036f2..0210667854 100644 --- a/drivers/spi/designware_spi.c +++ b/drivers/spi/designware_spi.c @@ -164,13 +164,13 @@ static void spi_hw_init(struct dw_spi_priv *priv) if (!priv->fifo_len) { u32 fifo; - for (fifo = 2; fifo <= 257; fifo++) { + for (fifo = 2; fifo <= 256; fifo++) { dw_writew(priv, DW_SPI_TXFLTR, fifo); if (fifo != dw_readw(priv, DW_SPI_TXFLTR)) break; } - priv->fifo_len = (fifo == 257) ? 0 : fifo; + priv->fifo_len = (fifo == 2) ? 0 : fifo - 1; dw_writew(priv, DW_SPI_TXFLTR, 0); } debug("%s: fifo_len=%d\n", __func__, priv->fifo_len); -- 2.39.5