| From d297933cc7fcfbaaf2d37570baac73287bf0357d Mon Sep 17 00:00:00 2001 |
| From: Axel Lin <axel.lin@ingics.com> |
| Date: Mon, 5 Jan 2015 09:32:56 +0800 |
| Subject: spi: dw: Fix detecting FIFO depth |
| |
| From: Axel Lin <axel.lin@ingics.com> |
| |
| commit d297933cc7fcfbaaf2d37570baac73287bf0357d upstream. |
| |
| 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> |
| Reviewed-and-tested-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com> |
| Signed-off-by: Mark Brown <broonie@kernel.org> |
| Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
| |
| --- |
| drivers/spi/spi-dw.c | 4 ++-- |
| 1 file changed, 2 insertions(+), 2 deletions(-) |
| |
| --- a/drivers/spi/spi-dw.c |
| +++ b/drivers/spi/spi-dw.c |
| @@ -621,13 +621,13 @@ static void spi_hw_init(struct dw_spi *d |
| if (!dws->fifo_len) { |
| u32 fifo; |
| |
| - for (fifo = 2; fifo <= 257; fifo++) { |
| + for (fifo = 2; fifo <= 256; fifo++) { |
| dw_writew(dws, DW_SPI_TXFLTR, fifo); |
| if (fifo != dw_readw(dws, DW_SPI_TXFLTR)) |
| break; |
| } |
| |
| - dws->fifo_len = (fifo == 257) ? 0 : fifo; |
| + dws->fifo_len = (fifo == 2) ? 0 : fifo - 1; |
| dw_writew(dws, DW_SPI_TXFLTR, 0); |
| } |
| } |