| From | lizf@kernel ... | Subject | [PATCH 3.4 173/176] spi: dw: revisit FIFO size detection again | Date | Thu, 9 Apr 2015 16:47:01 +0800 |
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From: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
3.4.107-rc1 review patch. If anyone has any objections, please let me know.
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commit 9d239d353c319f9ff884c287ce47feb7cdf60ddc upstream.
The commit d297933cc7fc (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: d297933cc7fc (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> Signed-off-by: Zefan Li <lizefan@huawei.com> --- drivers/spi/spi-dw.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/drivers/spi/spi-dw.c b/drivers/spi/spi-dw.c index 71ef1e4..cce2d7b 100644 --- a/drivers/spi/spi-dw.c +++ b/drivers/spi/spi-dw.c @@ -780,13 +780,13 @@ static void spi_hw_init(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; } - dws->fifo_len = (fifo == 2) ? 0 : fifo - 1; + dws->fifo_len = (fifo == 1) ? 0 : fifo; dw_writew(dws, DW_SPI_TXFLTR, 0); } } -- 1.9.1
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