| Message ID | 1549015162-17418-1-git-send-email-jmasson@baylibre.com (mailing list archive) |
|---|---|
| State | Superseded |
| Headers | show |
| Series | tty: serial: meson_uart: Add support for kernel debugger | expand |
On Fri, Feb 01, 2019 at 10:59:22AM +0100, Julien Masson wrote: > The kgdb invokes the poll_put_char and poll_get_char when communicating > with the host. This patch implement the serial polling hooks for the > meson_uart to be used for KGDB debugging over serial line. > > Signed-off-by: Julien Masson <jmasson@baylibre.com> > --- > It has been tested on "Le Potato" board: > https://libre.computer/products/boards/aml-s905x-cc/ > > Kernel command line arguments: > kgdboc=ttyAML0,115200 kgdbretry=4 nokaslr kgdbcon > > Kernel modules: > CONFIG_DEBUG_INFO=y > CONFIG_DEBUG_KERNEL=y > CONFIG_FRAME_POINTER=y > CONFIG_KGDB=y > CONFIG_KGDB_SERIAL_CONSOLE=y > > Warning: for single step instruction I had to apply this patch: > https://lore.kernel.org/patchwork/patch/562423/ > > drivers/tty/serial/meson_uart.c | 46 +++++++++++++++++++++++++++++++++++++++++ > 1 file changed, 46 insertions(+) > > diff --git a/drivers/tty/serial/meson_uart.c b/drivers/tty/serial/meson_uart.c > index 8a84259..49b20da 100644 > --- a/drivers/tty/serial/meson_uart.c > +++ b/drivers/tty/serial/meson_uart.c > @@ -426,6 +426,48 @@ static void meson_uart_config_port(struct uart_port *port, int flags) > } > } > > +#ifdef CONFIG_CONSOLE_POLL > +/* > + * Console polling routines for writing and reading from the uart while > + * in an interrupt or debug context (i.e. kgdb). > + */ > + > +static int meson_uart_poll_get_char(struct uart_port *port) > +{ > + u32 c; > + unsigned long flags; > + > + spin_lock_irqsave(&port->lock, flags); > + > + if (readl(port->membase + AML_UART_STATUS) & AML_UART_RX_EMPTY) > + c = NO_POLL_CHAR; > + else > + c = readl(port->membase + AML_UART_RFIFO); > + > + spin_unlock_irqrestore(&port->lock, flags); > + > + return c; > +} > + > +static void meson_uart_poll_put_char(struct uart_port *port, unsigned char c) > +{ > + unsigned long flags; > + > + spin_lock_irqsave(&port->lock, flags); > + > + while (!(readl(port->membase + AML_UART_STATUS) & AML_UART_TX_EMPTY)) > + cpu_relax(); Hello Perhaps you could use read_poll_timeout() ? This will also permit to handle the timeout case. Regards
On Fri 01 Feb 2019 at 11:10, Corentin Labbe <clabbe.montjoie@gmail.com> wrote: > On Fri, Feb 01, 2019 at 10:59:22AM +0100, Julien Masson wrote: >> The kgdb invokes the poll_put_char and poll_get_char when communicating >> with the host. This patch implement the serial polling hooks for the >> meson_uart to be used for KGDB debugging over serial line. >> >> Signed-off-by: Julien Masson <jmasson@baylibre.com> >> --- >> It has been tested on "Le Potato" board: >> https://libre.computer/products/boards/aml-s905x-cc/ >> >> Kernel command line arguments: >> kgdboc=ttyAML0,115200 kgdbretry=4 nokaslr kgdbcon >> >> Kernel modules: >> CONFIG_DEBUG_INFO=y >> CONFIG_DEBUG_KERNEL=y >> CONFIG_FRAME_POINTER=y >> CONFIG_KGDB=y >> CONFIG_KGDB_SERIAL_CONSOLE=y >> >> Warning: for single step instruction I had to apply this patch: >> https://lore.kernel.org/patchwork/patch/562423/ >> >> drivers/tty/serial/meson_uart.c | 46 +++++++++++++++++++++++++++++++++++++++++ >> 1 file changed, 46 insertions(+) >> >> diff --git a/drivers/tty/serial/meson_uart.c b/drivers/tty/serial/meson_uart.c >> index 8a84259..49b20da 100644 >> --- a/drivers/tty/serial/meson_uart.c >> +++ b/drivers/tty/serial/meson_uart.c >> @@ -426,6 +426,48 @@ static void meson_uart_config_port(struct uart_port *port, int flags) >> } >> } >> >> +#ifdef CONFIG_CONSOLE_POLL >> +/* >> + * Console polling routines for writing and reading from the uart while >> + * in an interrupt or debug context (i.e. kgdb). >> + */ >> + >> +static int meson_uart_poll_get_char(struct uart_port *port) >> +{ >> + u32 c; >> + unsigned long flags; >> + >> + spin_lock_irqsave(&port->lock, flags); >> + >> + if (readl(port->membase + AML_UART_STATUS) & AML_UART_RX_EMPTY) >> + c = NO_POLL_CHAR; >> + else >> + c = readl(port->membase + AML_UART_RFIFO); >> + >> + spin_unlock_irqrestore(&port->lock, flags); >> + >> + return c; >> +} >> + >> +static void meson_uart_poll_put_char(struct uart_port *port, unsigned char c) >> +{ >> + unsigned long flags; >> + >> + spin_lock_irqsave(&port->lock, flags); >> + >> + while (!(readl(port->membase + AML_UART_STATUS) & AML_UART_TX_EMPTY)) >> + cpu_relax(); > > Hello > > Perhaps you could use read_poll_timeout() ? > This will also permit to handle the timeout case. > > Regards Thanks for the tips Corentin. I tested with a poll of 5 usec and 1 msec of timeout. I had to use readl_poll_timeout_atomic(...) since I'm in atomic context (spinlock). I'll send a v2 of this patch. Regards
diff --git a/drivers/tty/serial/meson_uart.c b/drivers/tty/serial/meson_uart.c index 8a84259..49b20da 100644 --- a/drivers/tty/serial/meson_uart.c +++ b/drivers/tty/serial/meson_uart.c @@ -426,6 +426,48 @@ static void meson_uart_config_port(struct uart_port *port, int flags) } } +#ifdef CONFIG_CONSOLE_POLL +/* + * Console polling routines for writing and reading from the uart while + * in an interrupt or debug context (i.e. kgdb). + */ + +static int meson_uart_poll_get_char(struct uart_port *port) +{ + u32 c; + unsigned long flags; + + spin_lock_irqsave(&port->lock, flags); + + if (readl(port->membase + AML_UART_STATUS) & AML_UART_RX_EMPTY) + c = NO_POLL_CHAR; + else + c = readl(port->membase + AML_UART_RFIFO); + + spin_unlock_irqrestore(&port->lock, flags); + + return c; +} + +static void meson_uart_poll_put_char(struct uart_port *port, unsigned char c) +{ + unsigned long flags; + + spin_lock_irqsave(&port->lock, flags); + + while (!(readl(port->membase + AML_UART_STATUS) & AML_UART_TX_EMPTY)) + cpu_relax(); + + writel(c, port->membase + AML_UART_WFIFO); + + while (!(readl(port->membase + AML_UART_STATUS) & AML_UART_TX_EMPTY)) + cpu_relax(); + + spin_unlock_irqrestore(&port->lock, flags); +} + +#endif /* CONFIG_CONSOLE_POLL */ + static const struct uart_ops meson_uart_ops = { .set_mctrl = meson_uart_set_mctrl, .get_mctrl = meson_uart_get_mctrl, @@ -441,6 +483,10 @@ static const struct uart_ops meson_uart_ops = { .request_port = meson_uart_request_port, .release_port = meson_uart_release_port, .verify_port = meson_uart_verify_port, +#ifdef CONFIG_CONSOLE_POLL + .poll_get_char = meson_uart_poll_get_char, + .poll_put_char = meson_uart_poll_put_char, +#endif }; #ifdef CONFIG_SERIAL_MESON_CONSOLE
The kgdb invokes the poll_put_char and poll_get_char when communicating with the host. This patch implement the serial polling hooks for the meson_uart to be used for KGDB debugging over serial line. Signed-off-by: Julien Masson <jmasson@baylibre.com> --- It has been tested on "Le Potato" board: https://libre.computer/products/boards/aml-s905x-cc/ Kernel command line arguments: kgdboc=ttyAML0,115200 kgdbretry=4 nokaslr kgdbcon Kernel modules: CONFIG_DEBUG_INFO=y CONFIG_DEBUG_KERNEL=y CONFIG_FRAME_POINTER=y CONFIG_KGDB=y CONFIG_KGDB_SERIAL_CONSOLE=y Warning: for single step instruction I had to apply this patch: https://lore.kernel.org/patchwork/patch/562423/ drivers/tty/serial/meson_uart.c | 46 +++++++++++++++++++++++++++++++++++++++++ 1 file changed, 46 insertions(+)