| From | Ben Hutchings <> | Date | Tue, 17 Feb 2015 01:46:53 +0000 | Subject | [PATCH 3.2 080/152] spi: dw: Fix detecting FIFO depth |
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3.2.67-rc1 review patch. If anyone has any objections, please let me know.
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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> [bwh: Backported to 3.2: adjust context] Signed-off-by: Ben Hutchings <ben@decadent.org.uk> --- 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 @@ -786,13 +786,13 @@ 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); } }
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