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tty: serial: imx: initialize peripheral_config/peripheral_size for sdma config

Message ID 20220803065737.14752-1-sherry.sun@nxp.com
State New
Headers show
Series tty: serial: imx: initialize peripheral_config/peripheral_size for sdma config | expand

Commit Message

Sherry Sun Aug. 3, 2022, 6:57 a.m. UTC
Since commit 824a0a02cd74 ("dmaengine: imx-sdma: Add multi fifo support")
adds the use of dma_slave_config->peripheral_config/peripheral_size to
sdma driver, the client drivers like uart need to initialize the
peripheral_config/peripheral_size for sdma, otherwise, the random value
of local variable slave_config may cause unexpected peripheral_config
and make sdma mess up.

Signed-off-by: Sherry Sun <sherry.sun@nxp.com>
---
 drivers/tty/serial/imx.c | 4 ++++
 1 file changed, 4 insertions(+)

Comments

Ahmad Fatoum Aug. 3, 2022, 8:16 a.m. UTC | #1
Hello Sherry,

On 03.08.22 08:57, Sherry Sun wrote:
> Since commit 824a0a02cd74 ("dmaengine: imx-sdma: Add multi fifo support")
> adds the use of dma_slave_config->peripheral_config/peripheral_size to
> sdma driver, the client drivers like uart need to initialize the
> peripheral_config/peripheral_size for sdma, otherwise, the random value
> of local variable slave_config may cause unexpected peripheral_config
> and make sdma mess up.
> 

If this a fix, please add a Fixes: tag. I am not sure it is though,
see below.

> Signed-off-by: Sherry Sun <sherry.sun@nxp.com>
> ---
>  drivers/tty/serial/imx.c | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/drivers/tty/serial/imx.c b/drivers/tty/serial/imx.c
> index 522445a8f666..bb8c2a712e94 100644
> --- a/drivers/tty/serial/imx.c
> +++ b/drivers/tty/serial/imx.c
> @@ -1320,6 +1320,8 @@ static int imx_uart_dma_init(struct imx_port *sport)

This function starts with 

struct dma_slave_config slave_config = {};

>  	slave_config.src_addr_width = DMA_SLAVE_BUSWIDTH_1_BYTE;
>  	/* one byte less than the watermark level to enable the aging timer */
>  	slave_config.src_maxburst = RXTL_DMA - 1;
> +	slave_config.peripheral_config = NULL;
> +	slave_config.peripheral_size = 0;

So these are already zero-initialized.

>  	ret = dmaengine_slave_config(sport->dma_chan_rx, &slave_config);
>  	if (ret) {
>  		dev_err(dev, "error in RX dma configuration.\n");
> @@ -1346,6 +1348,8 @@ static int imx_uart_dma_init(struct imx_port *sport)
>  	slave_config.dst_addr = sport->port.mapbase + URTX0;
>  	slave_config.dst_addr_width = DMA_SLAVE_BUSWIDTH_1_BYTE;
>  	slave_config.dst_maxburst = TXTL_DMA;
> +	slave_config.peripheral_config = NULL;
> +	slave_config.peripheral_size = 0;

Not sure if this is required. If preceding dmaengine_slave_config()
indeed makes clearing necessary, you should note that in the commit
message.

Cheers,
Ahmad

>  	ret = dmaengine_slave_config(sport->dma_chan_tx, &slave_config);
>  	if (ret) {
>  		dev_err(dev, "error in TX dma configuration.");
Greg KH Aug. 3, 2022, 9:22 a.m. UTC | #2
On Wed, Aug 03, 2022 at 09:15:58AM +0000, Sherry Sun wrote:
> > On 03.08.22 08:57, Sherry Sun wrote:
> > > Since commit 824a0a02cd74 ("dmaengine: imx-sdma: Add multi fifo
> > > support") adds the use of
> > > dma_slave_config->peripheral_config/peripheral_size to sdma driver,
> > > the client drivers like uart need to initialize the
> > > peripheral_config/peripheral_size for sdma, otherwise, the random
> > > value of local variable slave_config may cause unexpected
> > peripheral_config and make sdma mess up.
> > >
> > 
> > If this a fix, please add a Fixes: tag. I am not sure it is though, see below.
> 
> Hi Ahmad, thanks for the comments.
> I don't think this patch is a fix for a specific commit, so we don't need the Fixes tag.
> 
> > 
> > > Signed-off-by: Sherry Sun <sherry.sun@nxp.com>
> > > ---
> > >  drivers/tty/serial/imx.c | 4 ++++
> > >  1 file changed, 4 insertions(+)
> > >
> > > diff --git a/drivers/tty/serial/imx.c b/drivers/tty/serial/imx.c index
> > > 522445a8f666..bb8c2a712e94 100644
> > > --- a/drivers/tty/serial/imx.c
> > > +++ b/drivers/tty/serial/imx.c
> > > @@ -1320,6 +1320,8 @@ static int imx_uart_dma_init(struct imx_port
> > > *sport)
> > 
> > This function starts with
> > 
> > struct dma_slave_config slave_config = {};
> > 
> > >  	slave_config.src_addr_width = DMA_SLAVE_BUSWIDTH_1_BYTE;
> > >  	/* one byte less than the watermark level to enable the aging timer
> > */
> > >  	slave_config.src_maxburst = RXTL_DMA - 1;
> > > +	slave_config.peripheral_config = NULL;
> > > +	slave_config.peripheral_size = 0;
> > 
> > So these are already zero-initialized.
> 
> I am not sure actually, I think initialize a struct with {} cannot guarantee that all members are initialized to 0, it may depend on the compiler.

Not true, it's part of the C standard somewhere...

thanks,

greg k-h
Uwe Kleine-König Aug. 3, 2022, 9:40 a.m. UTC | #3
On Wed, Aug 03, 2022 at 09:15:58AM +0000, Sherry Sun wrote:
> > On 03.08.22 08:57, Sherry Sun wrote:
> > > Since commit 824a0a02cd74 ("dmaengine: imx-sdma: Add multi fifo
> > > support") adds the use of
> > > dma_slave_config->peripheral_config/peripheral_size to sdma driver,
> > > the client drivers like uart need to initialize the
> > > peripheral_config/peripheral_size for sdma, otherwise, the random
> > > value of local variable slave_config may cause unexpected
> > peripheral_config and make sdma mess up.
> > >
> > 
> > If this a fix, please add a Fixes: tag. I am not sure it is though, see below.
> 
> Hi Ahmad, thanks for the comments.
> I don't think this patch is a fix for a specific commit, so we don't need the Fixes tag.
> 
> > 
> > > Signed-off-by: Sherry Sun <sherry.sun@nxp.com>
> > > ---
> > >  drivers/tty/serial/imx.c | 4 ++++
> > >  1 file changed, 4 insertions(+)
> > >
> > > diff --git a/drivers/tty/serial/imx.c b/drivers/tty/serial/imx.c index
> > > 522445a8f666..bb8c2a712e94 100644
> > > --- a/drivers/tty/serial/imx.c
> > > +++ b/drivers/tty/serial/imx.c
> > > @@ -1320,6 +1320,8 @@ static int imx_uart_dma_init(struct imx_port
> > > *sport)
> > 
> > This function starts with
> > 
> > struct dma_slave_config slave_config = {};
> > 
> > >  	slave_config.src_addr_width = DMA_SLAVE_BUSWIDTH_1_BYTE;
> > >  	/* one byte less than the watermark level to enable the aging timer
> > */
> > >  	slave_config.src_maxburst = RXTL_DMA - 1;
> > > +	slave_config.peripheral_config = NULL;
> > > +	slave_config.peripheral_size = 0;
> > 
> > So these are already zero-initialized.
> 
> I am not sure actually, I think initialize a struct with {} cannot
> guarantee that all members are initialized to 0, it may depend on the
> compiler.

I'm sure and even reverified in my C book[1].

	struct mystruct variable = {};

results in all components being initialized to their default initial
value (which is 0 for numbers and NULL for pointers). This works for
automatic variables since "Standard C" which should cover everthing that
is capable to compile today's kernel.

Best regards
Uwe

[1] C - A Reference Manual, 978-0130895929
diff mbox series

Patch

diff --git a/drivers/tty/serial/imx.c b/drivers/tty/serial/imx.c
index 522445a8f666..bb8c2a712e94 100644
--- a/drivers/tty/serial/imx.c
+++ b/drivers/tty/serial/imx.c
@@ -1320,6 +1320,8 @@  static int imx_uart_dma_init(struct imx_port *sport)
 	slave_config.src_addr_width = DMA_SLAVE_BUSWIDTH_1_BYTE;
 	/* one byte less than the watermark level to enable the aging timer */
 	slave_config.src_maxburst = RXTL_DMA - 1;
+	slave_config.peripheral_config = NULL;
+	slave_config.peripheral_size = 0;
 	ret = dmaengine_slave_config(sport->dma_chan_rx, &slave_config);
 	if (ret) {
 		dev_err(dev, "error in RX dma configuration.\n");
@@ -1346,6 +1348,8 @@  static int imx_uart_dma_init(struct imx_port *sport)
 	slave_config.dst_addr = sport->port.mapbase + URTX0;
 	slave_config.dst_addr_width = DMA_SLAVE_BUSWIDTH_1_BYTE;
 	slave_config.dst_maxburst = TXTL_DMA;
+	slave_config.peripheral_config = NULL;
+	slave_config.peripheral_size = 0;
 	ret = dmaengine_slave_config(sport->dma_chan_tx, &slave_config);
 	if (ret) {
 		dev_err(dev, "error in TX dma configuration.");