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

[Marek Vasut]

On 02/05/2017 05:36 PM, Fabio Estevam wrote:
> 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.

Yeah, it won't , see the commit that this patch fixes. It introduces a
bug and if you want DMA on MX6SX, this should be another separate patch.

>> 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.

Well yes, DMA is broken in 4.9 , that's why it's CC stable 4.9+ :)

> There is also this report from Clemens: https://lkml.org/lkml/2017/1/4/579
> 
> Could anyone run a git bisect?

Ummmmmmmm ... see above ? :)
Fixes: 1c06bde643d0 ("Allowing UART DMA to be configured on i.MX53")

-- 
Best regards,
Marek Vasut