From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Brownell Subject: [patch 2.6.28-rc6] spi: mpc52xx_psc_spi chipselect bugfix Date: Thu, 20 Nov 2008 21:26:22 -0800 Message-ID: <200811202126.23121.david-b@pacbell.net> Reply-To: dbrownell-Rn4VEauK+AKRv+LV9MX5uipxlwaOVQ5f@public.gmane.org Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Cc: spi-devel-general-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org To: Andrew Morton Return-path: Content-Disposition: inline List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: spi-devel-general-bounces-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org List-Id: linux-spi.vger.kernel.org From: Stefano Babic 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 --- drivers/spi/mpc52xx_psc_spi.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) --- 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 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 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) ------------------------------------------------------------------------- This SF.Net email is sponsored by the Moblin Your Move Developer's challenge Build the coolest Linux based applications with Moblin SDK & win great prizes Grand prize is a trip for two to an Open Source event anywhere in the world http://moblin-contest.org/redirect.php?banner_id=100&url=/