linux-kernel - Re: [PATCH] tty: serial: imx: initialize peripheral_config/peripheral

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Message-ID: <d4838245-030c-39b4-df4b-17b3b4c73a5b@pengutronix.de>
Date:   Wed, 3 Aug 2022 10:16:03 +0200
From:   Ahmad Fatoum <a.fatoum@...gutronix.de>
To:     Sherry Sun <sherry.sun@....com>, gregkh@...uxfoundation.org,
        jirislaby@...nel.org, shawnguo@...nel.org, s.hauer@...gutronix.de,
        kernel@...gutronix.de, festevam@...il.com
Cc:     linux-kernel@...r.kernel.org, linux-serial@...r.kernel.org,
        linux-imx@....com
Subject: Re: [PATCH] tty: serial: imx: initialize
 peripheral_config/peripheral_size for sdma config

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@....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.");


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