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@xxxxxxxxxxxx> > --- > 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
