From: Axel Lin Date: Mon, 5 Jan 2015 01:32:56 +0000 (+0800) Subject: spi: dw: Fix detecting FIFO depth X-Git-Tag: v3.2.67~73 X-Git-Url: https://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=250dbefd2d4437e39fef2ff3b0ee121267a5c688;p=pandora-kernel.git spi: dw: Fix detecting FIFO depth 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 Reviewed-and-tested-by: Andy Shevchenko Signed-off-by: Mark Brown [bwh: Backported to 3.2: adjust context] Signed-off-by: Ben Hutchings --- diff --git a/drivers/spi/spi-dw.c b/drivers/spi/spi-dw.c index 9eddaab7b915..bbdf0cf7434b 100644 --- a/drivers/spi/spi-dw.c +++ b/drivers/spi/spi-dw.c @@ -786,13 +786,13 @@ 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); } }