| Message ID | 1583224900-25824-1-git-send-email-vincent.chen@sifive.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | tty: serial: Add CONSOLE_POLL support to SiFive UART | expand |
On Tue, 03 Mar 2020 00:41:40 PST (-0800), vincent.chen@sifive.com wrote: > Add CONSOLE_POLL support for future KGDB porting. > > Signed-off-by: Vincent Chen <vincent.chen@sifive.com> > --- > drivers/tty/serial/sifive.c | 27 +++++++++++++++++++++++++++ > 1 file changed, 27 insertions(+) > > diff --git a/drivers/tty/serial/sifive.c b/drivers/tty/serial/sifive.c > index d5f81b98e4d7..acdbaca4de36 100644 > --- a/drivers/tty/serial/sifive.c > +++ b/drivers/tty/serial/sifive.c > @@ -818,6 +818,29 @@ static int __init sifive_serial_console_setup(struct console *co, char *options) > return uart_set_options(&ssp->port, co, baud, parity, bits, flow); > } > > +#ifdef CONFIG_CONSOLE_POLL > +static int sifive_serial_poll_get_char(struct uart_port *port) > +{ > + struct sifive_serial_port *ssp = port_to_sifive_serial_port(port); > + char is_empty, ch; > + > + ch = __ssp_receive_char(ssp, &is_empty); > + if (is_empty) > + return NO_POLL_CHAR; > + > + return ch; > +} > + > +static void sifive_serial_poll_put_char(struct uart_port *port, > + unsigned char c) > +{ > + struct sifive_serial_port *ssp = port_to_sifive_serial_port(port); > + > + sifive_serial_console_putchar(port, c); > + __ssp_wait_for_xmitr(ssp); So we still have that TX watermark bug in the SiFive UARTs. If this function is supposed to wait until the word is actually out on the line then this isn't sufficient, but if it's just supposed to wait until the next write won't block then this is fine. I'm not really a serial person, so mabye someone else knows? For those unfamiliar with the issue, there's a pretty good description in the patch to fix it https://github.com/sifive/sifive-blocks/pull/90 Poking around we don't have any PRE_RATE_CHANGE hook, so I'm going to take a whack at adding one -- not really related to this patch, though. > +} > +#endif /* CONFIG_CONSOLE_POLL */ > + > static struct uart_driver sifive_serial_uart_driver; > > static struct console sifive_serial_console = { > @@ -877,6 +900,10 @@ static const struct uart_ops sifive_serial_uops = { > .request_port = sifive_serial_request_port, > .config_port = sifive_serial_config_port, > .verify_port = sifive_serial_verify_port, > +#ifdef CONFIG_CONSOLE_POLL > + .poll_get_char = sifive_serial_poll_get_char, > + .poll_put_char = sifive_serial_poll_put_char, > +#endif > }; > > static struct uart_driver sifive_serial_uart_driver = {
On Fri, Mar 06, 2020 at 10:13:56AM -0800, Palmer Dabbelt wrote: > On Tue, 03 Mar 2020 00:41:40 PST (-0800), vincent.chen@sifive.com wrote: > > Add CONSOLE_POLL support for future KGDB porting. > > > > Signed-off-by: Vincent Chen <vincent.chen@sifive.com> > > --- > > drivers/tty/serial/sifive.c | 27 +++++++++++++++++++++++++++ > > 1 file changed, 27 insertions(+) > > > > diff --git a/drivers/tty/serial/sifive.c b/drivers/tty/serial/sifive.c > > index d5f81b98e4d7..acdbaca4de36 100644 > > --- a/drivers/tty/serial/sifive.c > > +++ b/drivers/tty/serial/sifive.c > > @@ -818,6 +818,29 @@ static int __init sifive_serial_console_setup(struct console *co, char *options) > > return uart_set_options(&ssp->port, co, baud, parity, bits, flow); > > } > > > > +#ifdef CONFIG_CONSOLE_POLL > > +static int sifive_serial_poll_get_char(struct uart_port *port) > > +{ > > + struct sifive_serial_port *ssp = port_to_sifive_serial_port(port); > > + char is_empty, ch; > > + > > + ch = __ssp_receive_char(ssp, &is_empty); > > + if (is_empty) > > + return NO_POLL_CHAR; > > + > > + return ch; > > +} > > + > > +static void sifive_serial_poll_put_char(struct uart_port *port, > > + unsigned char c) > > +{ > > + struct sifive_serial_port *ssp = port_to_sifive_serial_port(port); > > + > > + sifive_serial_console_putchar(port, c); > > + __ssp_wait_for_xmitr(ssp); > > So we still have that TX watermark bug in the SiFive UARTs. If this function > is supposed to wait until the word is actually out on the line then this isn't > sufficient, but if it's just supposed to wait until the next write won't block > then this is fine. > > I'm not really a serial person, so mabye someone else knows? For those > unfamiliar with the issue, there's a pretty good description in the patch to > fix it > > https://github.com/sifive/sifive-blocks/pull/90 > > Poking around we don't have any PRE_RATE_CHANGE hook, so I'm going to take a > whack at adding one -- not really related to this patch, though. I do have to drop this patch from my tree, as it breaks the build, so it needs to be redone anyway :( thanks, greg k-h
On Sat, Mar 7, 2020 at 2:13 AM Palmer Dabbelt <palmer@dabbelt.com> wrote: > > On Tue, 03 Mar 2020 00:41:40 PST (-0800), vincent.chen@sifive.com wrote: > > Add CONSOLE_POLL support for future KGDB porting. > > > > Signed-off-by: Vincent Chen <vincent.chen@sifive.com> > > --- > > drivers/tty/serial/sifive.c | 27 +++++++++++++++++++++++++++ > > 1 file changed, 27 insertions(+) > > > > diff --git a/drivers/tty/serial/sifive.c b/drivers/tty/serial/sifive.c > > index d5f81b98e4d7..acdbaca4de36 100644 > > --- a/drivers/tty/serial/sifive.c > > +++ b/drivers/tty/serial/sifive.c > > @@ -818,6 +818,29 @@ static int __init sifive_serial_console_setup(struct console *co, char *options) > > return uart_set_options(&ssp->port, co, baud, parity, bits, flow); > > } > > > > +#ifdef CONFIG_CONSOLE_POLL > > +static int sifive_serial_poll_get_char(struct uart_port *port) > > +{ > > + struct sifive_serial_port *ssp = port_to_sifive_serial_port(port); > > + char is_empty, ch; > > + > > + ch = __ssp_receive_char(ssp, &is_empty); > > + if (is_empty) > > + return NO_POLL_CHAR; > > + > > + return ch; > > +} > > + > > +static void sifive_serial_poll_put_char(struct uart_port *port, > > + unsigned char c) > > +{ > > + struct sifive_serial_port *ssp = port_to_sifive_serial_port(port); > > + > > + sifive_serial_console_putchar(port, c); > > + __ssp_wait_for_xmitr(ssp); > > So we still have that TX watermark bug in the SiFive UARTs. If this function > is supposed to wait until the word is actually out on the line then this isn't > sufficient, but if it's just supposed to wait until the next write won't block > then this is fine. > > I'm not really a serial person, so mabye someone else knows? For those > unfamiliar with the issue, there's a pretty good description in the patch to > fix it > > https://github.com/sifive/sifive-blocks/pull/90 > I read the description is this patch and it is very clear to understand the issue. Thanks for your sharing. In this case, the __ssp_wait_for_xmitr() is used to prevent the word in the TX FIFO buffer from being corrupted by the next write. Therefore, I think it might be sufficient to check thetxdata.full bit. Thanks for your comment.
On Sat, Mar 7, 2020 at 4:51 PM Greg KH <gregkh@linuxfoundation.org> wrote: > > On Fri, Mar 06, 2020 at 10:13:56AM -0800, Palmer Dabbelt wrote: > > On Tue, 03 Mar 2020 00:41:40 PST (-0800), vincent.chen@sifive.com wrote: > > > Add CONSOLE_POLL support for future KGDB porting. > > > > > > Signed-off-by: Vincent Chen <vincent.chen@sifive.com> > > > --- > > > drivers/tty/serial/sifive.c | 27 +++++++++++++++++++++++++++ > > > 1 file changed, 27 insertions(+) > > > > > > diff --git a/drivers/tty/serial/sifive.c b/drivers/tty/serial/sifive.c > > > index d5f81b98e4d7..acdbaca4de36 100644 > > > --- a/drivers/tty/serial/sifive.c > > > +++ b/drivers/tty/serial/sifive.c > > > @@ -818,6 +818,29 @@ static int __init sifive_serial_console_setup(struct console *co, char *options) > > > return uart_set_options(&ssp->port, co, baud, parity, bits, flow); > > > } > > > > > > +#ifdef CONFIG_CONSOLE_POLL > > > +static int sifive_serial_poll_get_char(struct uart_port *port) > > > +{ > > > + struct sifive_serial_port *ssp = port_to_sifive_serial_port(port); > > > + char is_empty, ch; > > > + > > > + ch = __ssp_receive_char(ssp, &is_empty); > > > + if (is_empty) > > > + return NO_POLL_CHAR; > > > + > > > + return ch; > > > +} > > > + > > > +static void sifive_serial_poll_put_char(struct uart_port *port, > > > + unsigned char c) > > > +{ > > > + struct sifive_serial_port *ssp = port_to_sifive_serial_port(port); > > > + > > > + sifive_serial_console_putchar(port, c); > > > + __ssp_wait_for_xmitr(ssp); > > > > So we still have that TX watermark bug in the SiFive UARTs. If this function > > is supposed to wait until the word is actually out on the line then this isn't > > sufficient, but if it's just supposed to wait until the next write won't block > > then this is fine. > > > > I'm not really a serial person, so mabye someone else knows? For those > > unfamiliar with the issue, there's a pretty good description in the patch to > > fix it > > > > https://github.com/sifive/sifive-blocks/pull/90 > > > > Poking around we don't have any PRE_RATE_CHANGE hook, so I'm going to take a > > whack at adding one -- not really related to this patch, though. > > I do have to drop this patch from my tree, as it breaks the build, so it > needs to be redone anyway :( > Thanks for the test to find out my mistake. I will fix it and resend the 2nd version patch. Thanks
diff --git a/drivers/tty/serial/sifive.c b/drivers/tty/serial/sifive.c index d5f81b98e4d7..acdbaca4de36 100644 --- a/drivers/tty/serial/sifive.c +++ b/drivers/tty/serial/sifive.c @@ -818,6 +818,29 @@ static int __init sifive_serial_console_setup(struct console *co, char *options) return uart_set_options(&ssp->port, co, baud, parity, bits, flow); } +#ifdef CONFIG_CONSOLE_POLL +static int sifive_serial_poll_get_char(struct uart_port *port) +{ + struct sifive_serial_port *ssp = port_to_sifive_serial_port(port); + char is_empty, ch; + + ch = __ssp_receive_char(ssp, &is_empty); + if (is_empty) + return NO_POLL_CHAR; + + return ch; +} + +static void sifive_serial_poll_put_char(struct uart_port *port, + unsigned char c) +{ + struct sifive_serial_port *ssp = port_to_sifive_serial_port(port); + + sifive_serial_console_putchar(port, c); + __ssp_wait_for_xmitr(ssp); +} +#endif /* CONFIG_CONSOLE_POLL */ + static struct uart_driver sifive_serial_uart_driver; static struct console sifive_serial_console = { @@ -877,6 +900,10 @@ static const struct uart_ops sifive_serial_uops = { .request_port = sifive_serial_request_port, .config_port = sifive_serial_config_port, .verify_port = sifive_serial_verify_port, +#ifdef CONFIG_CONSOLE_POLL + .poll_get_char = sifive_serial_poll_get_char, + .poll_put_char = sifive_serial_poll_put_char, +#endif }; static struct uart_driver sifive_serial_uart_driver = {
Add CONSOLE_POLL support for future KGDB porting. Signed-off-by: Vincent Chen <vincent.chen@sifive.com> --- drivers/tty/serial/sifive.c | 27 +++++++++++++++++++++++++++ 1 file changed, 27 insertions(+)