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 axel.lin@ingics.com --- The same fix is already applied to linux-spi tree: http://git.kernel.org/cgit/linux/kernel/git/broonie/spi.git/commit/?h=for-li...
This patch replaces my previous patch: http://lists.denx.de/pipermail/u-boot/2014-December/199228.html
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 98c9f03..0210667 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);