Commit d297933c authored Jan 05, 2015 by Axel Lin Committed by Mark Brown Jan 05, 2015

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

parent 97bf6af1

drivers/spi/spi-dw.c

+2 −2

Original line number	Original line	Diff line number	Diff line
	@@ -621,13 +621,13 @@ static void spi_hw_init(struct dw_spi *dws)
	if (!dws->fifo_len) {		if (!dws->fifo_len) {
	u32 fifo;		u32 fifo;

	for (fifo = 2; fifo <= 257; fifo++) {		for (fifo = 2; fifo <= 256; fifo++) {
	dw_writew(dws, DW_SPI_TXFLTR, fifo);		dw_writew(dws, DW_SPI_TXFLTR, fifo);
	if (fifo != dw_readw(dws, DW_SPI_TXFLTR))		if (fifo != dw_readw(dws, DW_SPI_TXFLTR))
	break;		break;
	}		}

	dws->fifo_len = (fifo == 257) ? 0 : fifo;		dws->fifo_len = (fifo == 2) ? 0 : fifo - 1;
	dw_writew(dws, DW_SPI_TXFLTR, 0);		dw_writew(dws, DW_SPI_TXFLTR, 0);
	}		}
	}		}

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