From mboxrd@z Thu Jan 1 00:00:00 1970 From: u.kleine-koenig@pengutronix.de (Uwe =?iso-8859-1?Q?Kleine-K=F6nig?=) Date: Wed, 13 Oct 2010 10:46:10 +0200 Subject: [PATCH] ARM: imx serial driver: fix resume In-Reply-To: <20101012183239.GG7159@buzzloop.caiaq.de> References: <1286384236-4241-1-git-send-email-daniel@caiaq.de> <20101012175658.GQ29673@pengutronix.de> <20101012183239.GG7159@buzzloop.caiaq.de> Message-ID: <20101013084610.GA21498@pengutronix.de> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On Tue, Oct 12, 2010 at 08:32:39PM +0200, Daniel Mack wrote: > On Tue, Oct 12, 2010 at 07:56:58PM +0200, Uwe Kleine-K?nig wrote: > > On Wed, Oct 06, 2010 at 06:57:16PM +0200, Daniel Mack wrote: > > > From: Volker Ernst > > > > > > I just came across a bug in the IMX31 serial driver which is still > > > present in the newest kernels and which prevents successful > > > resume-operation for the IMX31 serial ports. > > > > > > What happens is that in "drivers/serial/imx.c" on resume function > > > "serial_imx_resume" gets called. This function in turn calls > > > "uart_resume_port" (in the generic serial driver "serial_core.c"), > > > which in turn calls "imx_start_tx" in "imx.c" (in case the SIO-port > > > was really suspended) which in turn calls "imx_transmit_buffer". > > > > > > However calling "imx_transmit_buffer" with an empty TX-fifo (as is > > > usually the case) will result in the serial port starting to transmit > > > (actually the old [already sent] tx-buffer), as there is no check if > > > the tx-buffer is empty before starting to feed tx-fifo-data to the > > > serial port hardware. > > > > > > Signed-off-by: Volker Ernst > > > Cc: Daniel Mack > > > Cc: Andy Green > > > --- > > > > > > Volker did all the work on this, he just doesn't want to push his great > > > contributions upstream, so I do it for him :) > > > > > > > > > drivers/serial/imx.c | 4 ++-- > > > 1 files changed, 2 insertions(+), 2 deletions(-) > > > > > > diff --git a/drivers/serial/imx.c b/drivers/serial/imx.c > > > index 66ecc7a..0170119 100644 > > > --- a/drivers/serial/imx.c > > > +++ b/drivers/serial/imx.c > > > @@ -328,13 +328,13 @@ static inline void imx_transmit_buffer(struct imx_port *sport) > > > struct circ_buf *xmit = &sport->port.state->xmit; > > > > > > while (!(readl(sport->port.membase + UTS) & UTS_TXFULL)) { > > > + if (uart_circ_empty(xmit)) > > > + break; > > > /* send xmit->buf[xmit->tail] > > > * out the port here */ > > > writel(xmit->buf[xmit->tail], sport->port.membase + URTX0); > > > xmit->tail = (xmit->tail + 1) & (UART_XMIT_SIZE - 1); > > > sport->port.icount.tx++; > > > - if (uart_circ_empty(xmit)) > > > - break; > > > } > > > > > > if (uart_circ_chars_pending(xmit) < WAKEUP_CHARS) > > I needed that patch now, too, though in a different situation. I havn't > > investigated the details yet, but I think the problem is that > > imx_transmit_buffer is called, too, when using handshaking and the other > > side starts to be ready. > > > > You can count that as an Acked-by: me, preferably with the check added > > to the while condition as suggested in a different mail of this thread. > > Ok, thanks. However, I can not test this myself - Volker, can you try > the patch Uwe sent along some days ago? I'm currently working on an other issue with the driver that will result in a few patches. So I can just pick up this patch en passant and look to get it into mainline. Still a fixed patch or an Ack would be fine. Best regards Uwe -- Pengutronix e.K. | Uwe Kleine-K?nig | Industrial Linux Solutions | http://www.pengutronix.de/ |