From b6127ecae5eeca912b31d748b0e91518c3700f75 Mon Sep 17 00:00:00 2001 From: Anatolij Gustschin Date: Wed, 13 Mar 2013 14:57:43 +0100 Subject: [PATCH] spi/mpc512x-psc: optionally keep PSC SS asserted across xfer segmensts commit 1ad849aee5f53353ed88d9cd3d68a51b03a7d44f upstream. Some SPI slave devices require asserted chip select signal across multiple transfer segments of an SPI message. Currently the driver always de-asserts the internal SS signal for every single transfer segment of the message and ignores the 'cs_change' flag of the transfer description. Disable the internal chip select (SS) only if this is needed and indicated by the 'cs_change' flag. Without this change, each partial transfer of a surrounding multi-part SPI transaction might erroneously change the SS signal, which might prevent slaves from answering the request that was sent in a previous transfer segment because the transaction could be considered aborted (SS was de-asserted before reading the response). Reported-by: Gerhard Sittig Signed-off-by: Anatolij Gustschin Signed-off-by: Mark Brown Signed-off-by: Ben Hutchings --- drivers/spi/spi-mpc512x-psc.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/spi/spi-mpc512x-psc.c b/drivers/spi/spi-mpc512x-psc.c index 4c63f772780a..2e2b04fc065d 100644 --- a/drivers/spi/spi-mpc512x-psc.c +++ b/drivers/spi/spi-mpc512x-psc.c @@ -164,7 +164,7 @@ static int mpc512x_psc_spi_transfer_rxtx(struct spi_device *spi, for (i = count; i > 0; i--) { data = tx_buf ? *tx_buf++ : 0; - if (len == EOFBYTE) + if (len == EOFBYTE && t->cs_change) setbits32(&fifo->txcmd, MPC512x_PSC_FIFO_EOF); out_8(&fifo->txdata_8, data); len--; -- 2.39.2