[PATCH] serial: imx: Only enable UART DMA on i.MX6Q and i.MX53

[Fabio Estevam]

On Sun, Feb 5, 2017 at 12:56 PM, Fabio Estevam <fabio.estevam at nxp.com> wrote:
> [Sorry, for the top-posting]
>
>
> imx6sx uart should be of a IMX6Q_UART instead.
>
>
> Does this patch fix the issue?

It seems this dts change will not fix the problem.

> From: Kai Ruhnau <kai.ruhnau at target-sg.com>
>
> In 1c06bde6 with the introduction of DMA support for the i.MX53 platform,
> DMA was enabled for all platforms instead. On an i.MX6SX (which is a
> IMX21_UART), this breaks gpsd talking to an UART module with
>
>  imx-uart 21f4000.serial: DMA transaction error.
>
> This patch makes sure, UART DMA is only activated for i.MX53 and i.MX6Q.
>
> Signed-off-by: Kai Ruhnau <kai.ruhnau at target-sg.com>
> Reviewed-by: Marek Vasut <marex at denx.de>
> Fixes: 1c06bde643d0 ("Allowing UART DMA to be configured on i.MX53")
> Cc: <stable at vger.kernel.org> # 4.9+
> Cc: Fabio Estevam <fabio.estevam at nxp.com>
> Cc: Martyn Welch <martyn.welch at collabora.co.uk>
> Cc: Shawn Guo <shawnguo at kernel.org>
> ---
>  drivers/tty/serial/imx.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/tty/serial/imx.c b/drivers/tty/serial/imx.c
> index a70356d..8e2b5f2 100644
> --- a/drivers/tty/serial/imx.c
> +++ b/drivers/tty/serial/imx.c
> @@ -1269,7 +1269,8 @@ static int imx_startup(struct uart_port *port)
>          writel(temp & ~UCR4_DREN, sport->port.membase + UCR4);
>
>          /* Can we enable the DMA support? */
> -       if (!uart_console(port) && !sport->dma_is_inited)
> +       if ((is_imx6q_uart(sport)  || is_imx53_uart(sport)) &&
> +           !uart_console(port) && !sport->dma_is_inited)
>                  imx_uart_dma_init(sport);

Looks like imx serial DMA is broken in 4.9.

There is also this report from Clemens: https://lkml.org/lkml/2017/1/4/579

Could anyone run a git bisect?