From: Andy Shevchenko Date: Wed, 25 Feb 2015 09:39:36 +0000 (+0200) Subject: spi: dw: revisit FIFO size detection again X-Git-Tag: v4.0-rc4~31^2^4~1 X-Git-Url: https://asedeno.scripts.mit.edu/gitweb/?a=commitdiff_plain;h=9d239d353c319f9ff884c287ce47feb7cdf60ddc;p=linux.git spi: dw: revisit FIFO size detection again 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 Signed-off-by: Andy Shevchenko Signed-off-by: Mark Brown Cc: stable@vger.kernel.org --- diff --git a/drivers/spi/spi-dw.c b/drivers/spi/spi-dw.c index 5a97a62b298a..4847afba89f4 100644 --- a/drivers/spi/spi-dw.c +++ b/drivers/spi/spi-dw.c @@ -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); } }