Re: [PATCH v2] serial: sprd: Add polling IO support
Baolin Wang 于2019年9月19日周四 上午11:21写道：
>
> Hi,
>
> On Thu, 19 Sep 2019 at 11:10, Lanqing Liu wrote:
> >
> > In order to access the UART without the interrupts, the kernel uses
> > the basic polling methods for IO with the device. With these methods
> > implemented, it is now possible to enable kgdb during early boot over
> > serial.
> >
> > Signed-off-by: Lanqing Liu
> > ---
> > Change from v1:
> > - Add poll_init() support.
>
> Looks good to me and the KGDB can work well on my board, so feel free
> to add my tags:
> Reviewed-by: Baolin Wang
> Tested-by: Baolin Wang
>
ok, thanks
> > ---
> > drivers/tty/serial/sprd_serial.c | 33 +
> > 1 file changed, 33 insertions(+)
> >
> > diff --git a/drivers/tty/serial/sprd_serial.c
> > b/drivers/tty/serial/sprd_serial.c
> > index 73d71a4..d833160 100644
> > --- a/drivers/tty/serial/sprd_serial.c
> > +++ b/drivers/tty/serial/sprd_serial.c
> > @@ -911,6 +911,34 @@ static void sprd_pm(struct uart_port *port, unsigned
> > int state,
> > }
> > }
> >
> > +#ifdef CONFIG_CONSOLE_POLL
> > +static int sprd_poll_init(struct uart_port *port)
> > +{
> > + if (port->state->pm_state != UART_PM_STATE_ON) {
> > + sprd_pm(port, UART_PM_STATE_ON, 0);
> > + port->state->pm_state = UART_PM_STATE_ON;
> > + }
> > +
> > + return 0;
> > +}
> > +
> > +static int sprd_poll_get_char(struct uart_port *port)
> > +{
> > + while (!(serial_in(port, SPRD_STS1) & SPRD_RX_FIFO_CNT_MASK))
> > + cpu_relax();
> > +
> > + return serial_in(port, SPRD_RXD);
> > +}
> > +
> > +static void sprd_poll_put_char(struct uart_port *port, unsigned char ch)
> > +{
> > + while (serial_in(port, SPRD_STS1) & SPRD_TX_FIFO_CNT_MASK)
> > + cpu_relax();
> > +
> > + serial_out(port, SPRD_TXD, ch);
> > +}
> > +#endif
> > +
> > static const struct uart_ops serial_sprd_ops = {
> > .tx_empty = sprd_tx_empty,
> > .get_mctrl = sprd_get_mctrl,
> > @@ -928,6 +956,11 @@ static void sprd_pm(struct uart_port *port, unsigned
> > int state,
> > .config_port = sprd_config_port,
> > .verify_port = sprd_verify_port,
> > .pm = sprd_pm,
> > +#ifdef CONFIG_CONSOLE_POLL
> > + .poll_init = sprd_poll_init,
> > + .poll_get_char = sprd_poll_get_char,
> > + .poll_put_char = sprd_poll_put_char,
> > +#endif
> > };
> >
> > #ifdef CONFIG_SERIAL_SPRD_CONSOLE
> > --
> > 1.9.1
> >
>
>
> --
> Baolin Wang
> Best Regards
Re: [PATCH] serial: sprd: Add polling IO support
Baolin Wang 于2019年9月18日周三 下午8:10写道：
>
> Hi Lanqing,
>
> On Wed, 18 Sep 2019 at 16:16, Lanqing Liu wrote:
> >
> > In order to access the UART without the interrupts, the kernel uses
> > the basic polling methods for IO with the device. With these methods
> > implemented, it is now possible to enable kgdb during early boot over
> > serial.
> >
> > Signed-off-by: Lanqing Liu
> > ---
> > drivers/tty/serial/sprd_serial.c | 22 ++
> > 1 file changed, 22 insertions(+)
> >
> > diff --git a/drivers/tty/serial/sprd_serial.c
> > b/drivers/tty/serial/sprd_serial.c
> > index 73d71a4..579ab41 100644
> > --- a/drivers/tty/serial/sprd_serial.c
> > +++ b/drivers/tty/serial/sprd_serial.c
> > @@ -911,6 +911,24 @@ static void sprd_pm(struct uart_port *port, unsigned
> > int state,
> > }
> > }
> >
> > +#ifdef CONFIG_CONSOLE_POLL
> > +static int sprd_poll_get_char(struct uart_port *port)
> > +{
> > + while (!(serial_in(port, SPRD_STS1) & SPRD_RX_FIFO_CNT_MASK))
> > + cpu_relax();
> > +
> > + return serial_in(port, SPRD_RXD);
> > +}
> > +
> > +static void sprd_poll_put_char(struct uart_port *port, unsigned char ch)
> > +{
> > + while (serial_in(port, SPRD_STS1) & SPRD_TX_FIFO_CNT_MASK)
> > + cpu_relax();
> > +
> > + serial_out(port, SPRD_TXD, ch);
> > +}
> > +#endif
>
> When I tested your patch, I found only one case can work if the port
> used by KGDB is same with the port selected as console, which means
> this port will be powered on all the time. We had implemented the
> power management for the UART ports, so I think you should enable the
> clock for the port used by KGDB in poll_init(), then other ports can
> be used by KGDB.
>
Yes, agree with you. I will add poll_init() support. Thanks for your
comments.
> > +
> > static const struct uart_ops serial_sprd_ops = {
> > .tx_empty = sprd_tx_empty,
> > .get_mctrl = sprd_get_mctrl,
> > @@ -928,6 +946,10 @@ static void sprd_pm(struct uart_port *port, unsigned
> > int state,
> > .config_port = sprd_config_port,
> > .verify_port = sprd_verify_port,
> > .pm = sprd_pm,
> > +#ifdef CONFIG_CONSOLE_POLL
> > + .poll_get_char = sprd_poll_get_char,
> > + .poll_put_char = sprd_poll_put_char,
> > +#endif
> > };
> >
> > #ifdef CONFIG_SERIAL_SPRD_CONSOLE
> > --
> > 1.9.1
> >
>
>
> --
> Baolin Wang
> Best Regards
Re: [PATCH] tty: serial_core: Fix the incorrect configuration of baud rate and data length at the console serial port resume
Johan Hovold 于2019年5月14日周二 下午3:35写道：
>
> On Thu, May 09, 2019 at 01:42:39PM +0800, Lanqing Liu wrote:
> > When userspace opens a serial port for console, uart_port_startup()
> > is called. This function assigns the uport->cons->cflag value to
> > TTY->termios.c_cflag, then it is cleared to 0. When the user space
> > closes this serial port, the TTY structure will be released, and at
> > this time uport->cons->cflag has also been cleared.
> >
> > On the Spreadtrum platform, in some special scenarios, like charging mode,
> > userspace needs to close the console, which means the uport->cons->cflag
> > has also been cleared. But printing logs is still needed in the kernel. So
> > when system enters suspend and resume, the console needs to be configure
> > the baud rate and data length of the serial port according to its own cflag
> > when resuming the console port. At this time, the cflag is 0, which will
> > cause serial port to produce configuration errors that do not meet user
> > expectations.
>
> This is actually yet another regression due to 761ed4a94582 ("tty:
> serial_core: convert uart_close to use tty_port_close") which
> incidentally removed the call to uart_shutdown() where the cflag was
> being saved precisely to avoid the problem you're describing:
>
> ae84db9661ca ("serial: core: Preserve termios c_cflag for console
> resume")
Yes, agree with you.
>
> Judging from a quick look it seems the xmit buf, which is released in
> that function may now be leaking too.
We haven't found this issue before, but we can try to reproduce it on
our platform.
>
> > To fix this, assigning the TTY->termios.c_cflag value to uport->cons->cflag
> > before the userspace closes this console serial port. It will ensure that
> > the correct cflag value can be gotten when the console serial port was
> > resumed.
>
> Not sure this is the right fix, but I don't have time to look at this
> right now.
OK. Thanks for your comments.
