From mboxrd@z Thu Jan 1 00:00:00 1970 From: clemens.gruber@pqgruber.com (Clemens Gruber) Date: Sun, 5 Feb 2017 18:51:32 +0100 Subject: [PATCH] serial: imx: Only enable UART DMA on i.MX6Q and i.MX53 In-Reply-To: References: <20170204213931.3566-1-marex@denx.de> Message-ID: <20170205175132.GA2182@archie.localdomain> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On Sun, Feb 05, 2017 at 02:36:10PM -0200, Fabio Estevam wrote: > On Sun, Feb 5, 2017 at 12:56 PM, Fabio Estevam 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 > > > > 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 > > Reviewed-by: Marek Vasut > > Fixes: 1c06bde643d0 ("Allowing UART DMA to be configured on i.MX53") > > Cc: # 4.9+ > > Cc: Fabio Estevam > > Cc: Martyn Welch > > Cc: Shawn Guo > > --- > > 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 are probably two separate problems: A) I also observed the DMA transaction error message when I used the ROM SDMA scripts. Seems to affect single- and multi-core systems and is fixed by: github.com/Freescale/linux-fslc/commit/a2ec8df37f5d (?) This is also not RS-485 specific, but affects RS-232 too. B) The RS-485 DMA problem I reported, which only affects multi-core systems. RS-232 DMA is not affected. > > There is also this report from Clemens: https://lkml.org/lkml/2017/1/4/579 > > Could anyone run a git bisect? I reverted tty/serial/imx.c to the first implementation of RS-485, namely to commit 17b8f2a3fdca ("serial: imx: add support for half duplex rs485"). Also had to add "fsl," in front of uart-has-rts-cts in the DT. But it does not work either (same behavior). Looks like RS-485 DMA never worked on SMP systems..? It's still a mistery to me what is causing the xmit->tail index to walk over the xmit->head index, leading to the rest of the whole UART_XMIT_SIZE buffer to be sent out. But it must be connected to the transmit-complete interrupt, because if I disable it, this does not happen. Thanks, Clemens