spi: dw: Fix detecting FIFO depth

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>
Cc: stable@vger.kernel.org
This commit is contained in:
Axel Lin 2015-01-05 09:32:56 +08:00 committed by Mark Brown
parent 97bf6af1f9
commit d297933cc7
1 changed files with 2 additions and 2 deletions

View File

@ -621,13 +621,13 @@ static void spi_hw_init(struct dw_spi *dws)
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);
}
}