From b7d271df873c5121a4ca1c70dea126b5920ec2f1 Mon Sep 17 00:00:00 2001 From: Stefano Babic Date: Mon, 1 Dec 2008 13:13:53 -0800 Subject: [PATCH] spi: mpc52xx_psc_spi chipselect bugfix According to the manual the "tdfOnExit" flag must be set on the last byte we want to send. The PSC controller holds SS low until the flag is set. However, the flag was set always on the last byte of the FIFO, independently if it is the last byte of the transfer. This generates spurious toggling of the SS signals that breaks the protocol of some peripherals. Fix. Signed-off-by: Stefano Babic Acked-by: Grant Likely Signed-off-by: David Brownell Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- drivers/spi/mpc52xx_psc_spi.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/drivers/spi/mpc52xx_psc_spi.c b/drivers/spi/mpc52xx_psc_spi.c index 0debe11b67b..3b97803e1d1 100644 --- a/drivers/spi/mpc52xx_psc_spi.c +++ b/drivers/spi/mpc52xx_psc_spi.c @@ -142,6 +142,7 @@ static int mpc52xx_psc_spi_transfer_rxtx(struct spi_device *spi, unsigned rfalarm; unsigned send_at_once = MPC52xx_PSC_BUFSIZE; unsigned recv_at_once; + int last_block = 0; if (!t->tx_buf && !t->rx_buf && t->len) return -EINVAL; @@ -151,15 +152,17 @@ static int mpc52xx_psc_spi_transfer_rxtx(struct spi_device *spi, while (rb < t->len) { if (t->len - rb > MPC52xx_PSC_BUFSIZE) { rfalarm = MPC52xx_PSC_RFALARM; + last_block = 0; } else { send_at_once = t->len - sb; rfalarm = MPC52xx_PSC_BUFSIZE - (t->len - rb); + last_block = 1; } dev_dbg(&spi->dev, "send %d bytes...\n", send_at_once); for (; send_at_once; sb++, send_at_once--) { /* set EOF flag before the last word is sent */ - if (send_at_once == 1) + if (send_at_once == 1 && last_block) out_8(&psc->ircr2, 0x01); if (tx_buf) -- 2.41.1