Commit 9d239d35 authored Feb 25, 2015 by Andy Shevchenko Committed by Mark Brown Feb 26, 2015

spi: dw: revisit FIFO size detection again



The commit d297933c (spi: dw: Fix detecting FIFO depth) tries to fix the
logic of the FIFO detection based on the description on the comments. However,
there is a slight difference between numbers in TX Level and TX FIFO size.

So, 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.

This patch fixes it eventually right.

Fixes: d297933c (spi: dw: Fix detecting FIFO depth)
Reviewed-by: Axel Lin <axel.lin@ingics.com>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Mark Brown <broonie@kernel.org>
Cc: stable@vger.kernel.org

parent 307ed83c

drivers/spi/spi-dw.c

+2 −2

Original line number	Diff line number	Diff line
		@@ -621,14 +621,14 @@ static void spi_hw_init(struct device dev, struct dw_spi dws)
		if (!dws->fifo_len) {
		u32 fifo;

		for (fifo = 2; fifo <= 256; fifo++) {
		for (fifo = 1; fifo < 256; fifo++) {
		dw_writew(dws, DW_SPI_TXFLTR, fifo);
		if (fifo != dw_readw(dws, DW_SPI_TXFLTR))
		break;
		}
		dw_writew(dws, DW_SPI_TXFLTR, 0);

		dws->fifo_len = (fifo == 2) ? 0 : fifo - 1;
		dws->fifo_len = (fifo == 1) ? 0 : fifo;
		dev_dbg(dev, "Detected FIFO size: %u bytes\n", dws->fifo_len);
		}
		}