Hello Romain,

On Wed, Jul 05, 2017 at 12:14:57PM +0200, Romain Perier wrote:

Le 03/07/2017 ? 08:52, Uwe Kleine-K?nig a ?crit :

quoted

On Fri, Jun 30, 2017 at 02:13:29PM +0200, Lothar Wa?mann wrote:

quoted

On Fri, 30 Jun 2017 14:04:42 +0200 Romain Perier wrote:

quoted

From: Nandor Han <redacted>

Initialize both dma_is_{rx|tx}ing variables when DMA is enabled to avoid
checking uninitialized variables if port shutdown is requested before
DMA channels get a chance to start.

Signed-off-by: Nandor Han <redacted>
Signed-off-by: Romain Perier <redacted>
---
 drivers/tty/serial/imx.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/tty/serial/imx.c b/drivers/tty/serial/imx.c
index 188063d..81fb413 100644
--- a/drivers/tty/serial/imx.c
+++ b/drivers/tty/serial/imx.c

@@ -1225,6 +1225,9 @@ static void imx_enable_dma(struct imx_port *sport)
 
 	imx_setup_ufcr(sport, TXTL_DMA, RXTL_DMA);
 
+	sport->dma_is_rxing = 0;
+	sport->dma_is_txing = 0;
+
 	sport->dma_is_enabled = 1;
 }
 

sport is devm_kzalloc()ed, so the variables are initialized to 0 anyway.

I'd agree to Lothar's statement. Did you find this issue by inspection,
or does it fix a compiler warning? Do you think there is an actual
problem?

Best regards
Uwe

What does happen if the UART port is shutdown and then re-enabled ? I
don't think that kzalloc will work in this case

imx_shutdown has:

        if (sport->dma_is_enabled) {
		sport->dma_is_rxing = 0;
		sport->dma_is_txing = 0;

which might be good enough. Can dma_is_[rt]xing be != 0 if
dma_is_enabled is false? It seems it cannot, the only place where
dma_is_enabled is set to 0 (apart from the kzalloc where dma_is_[rt]xing
is set to zero) is imx_disable_dma(). The only caller sets both
dma_is_[rt]xing to zero before.

So this patch should be dropped or its commit log improved to point out
the actual problem.

Best regards
Uwe

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Pengutronix e.K.                           | Uwe Kleine-K?nig            |
Industrial Linux Solutions                 | http://www.pengutronix.de/  |