By specification the FIFO size would be in a range 2-256 bytes. From TX Level
prospective it means we can set threshold in the range 0-(FIFO size - 1) bytes.
Hence there are currently two issues:
a) FIFO size 2 bytes is actually skipped since TX Level is 1 bit and could be
either 0 or 1 byte;
b) FIFO size is incorrectly decreased by 1 which already done by meaning of
TX Level register.
Fixes: 501943696ea4 (spi: designware_spi: Fix detecting FIFO depth)
Signed-off-by: Andy Shevchenko <andriy.shevche...@linux.intel.com>
Signed-off-by: Axel Lin <axel....@ingics.com>
---
This fix is from linux-spi tree:
http://git.kernel.org/cgit/linux/kernel/git/broonie/spi.git/commit/?h=for-linus&id=9d239d353c319f9ff884c287ce47feb7cdf60ddc
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 2624844..8f5c0fc 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 <= 256; fifo++) {
+ for (fifo = 1; fifo < 256; fifo++) {
dw_writew(priv, DW_SPI_TXFLTR, fifo);
if (fifo != dw_readw(priv, DW_SPI_TXFLTR))
break;
}
- priv->fifo_len = (fifo == 2) ? 0 : fifo - 1;
+ priv->fifo_len = (fifo == 1) ? 0 : fifo;
dw_writew(priv, DW_SPI_TXFLTR, 0);
}
debug("%s: fifo_len=%d\n", __func__, priv->fifo_len);
--
1.9.1
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