| Message ID | 76cf9ce9cbf9dcdf78bc00ce7a919db1776ebce1.1712309058.git.esben@geanix.com |
|---|---|
| State | Superseded |
| Headers | show |
| Series | [1/2] serial: imx: Introduce timeout when waiting on transmitter empty | expand |
Fabio Estevam <festevam@gmail.com> writes: > On Fri, Apr 5, 2024 at 6:25 AM Esben Haabendal <esben@geanix.com> wrote: >> >> By waiting at most 1 second for USR2_TXDC to be set, we avoid a potentital > > s/potentital/potential Thanks, fixing. > Could you elaborate on this deadlock? Have you seen it in practice? I cannot say for sure if I have seen it. But in some cases, that is exactly what you would see. Nothing. If it would occur during shutdown, the console would simply stop/block, and you would see nothing. > Should a Fixes tag be added? Which commit should I add to that tag? The polling without timeout dates back to at least 2.6.12-rc2. /Esben
Marc Kleine-Budde <mkl@pengutronix.de> writes: > On 05.04.2024 19:22:29, Esben Haabendal wrote: >> Marc Kleine-Budde <mkl@pengutronix.de> writes: >> >> > On 05.04.2024 11:25:13, Esben Haabendal wrote: >> >> By waiting at most 1 second for USR2_TXDC to be set, we avoid a potentital >> >> deadlock. >> >> >> >> In case of the timeout, there is not much we can do, so we simply ignore >> >> the transmitter state and optimistically try to continue. >> >> >> >> Signed-off-by: Esben Haabendal <esben@geanix.com> >> >> Acked-by: Marc Kleine-Budde <mkl@pengutronix.de> >> > >> > Where's the cover letter and patch 2/2? Have a look at b4 [1], it's a >> > great tool to help you with sending git patch series. >> >> It is left out on purpose. >> >> This patch is a stand-alone patch as it is. The other part of the series >> you are talking about is not going to mainline for now. It needs still >> quite some work, and will only go in after all the other printk stuff. >> >> I hope we can merge this patch as it to mainline now, instead of piling >> up more than necessary in the rt tree. > > Ok, then send it as patch 1/1. Sure. Sorry about that. /Esben
diff --git a/drivers/tty/serial/imx.c b/drivers/tty/serial/imx.c index e14813250616..09c1678ddfd4 100644 --- a/drivers/tty/serial/imx.c +++ b/drivers/tty/serial/imx.c @@ -26,6 +26,7 @@ #include <linux/slab.h> #include <linux/of.h> #include <linux/io.h> +#include <linux/iopoll.h> #include <linux/dma-mapping.h> #include <asm/irq.h> @@ -2010,7 +2011,7 @@ imx_uart_console_write(struct console *co, const char *s, unsigned int count) struct imx_port *sport = imx_uart_ports[co->index]; struct imx_port_ucrs old_ucr; unsigned long flags; - unsigned int ucr1; + unsigned int ucr1, usr2; int locked = 1; if (sport->port.sysrq) @@ -2041,8 +2042,8 @@ imx_uart_console_write(struct console *co, const char *s, unsigned int count) * Finally, wait for transmitter to become empty * and restore UCR1/2/3 */ - while (!(imx_uart_readl(sport, USR2) & USR2_TXDC)); - + read_poll_timeout_atomic(imx_uart_readl, usr2, usr2 & USR2_TXDC, + 0, USEC_PER_SEC, false, sport, USR2); imx_uart_ucrs_restore(sport, &old_ucr); if (locked)