* [PATCH v2 0/2] serial: 8250_early: simplify serial_putc() @ 2015-10-24 4:17 Masahiro Yamada 2015-10-24 4:17 ` [PATCH v2 1/2] serial: 8250_early: do not save and restore IER in write callback Masahiro Yamada 2015-10-24 4:17 ` [PATCH v2 2/2] serial: 8250_early: squash wait_for_xmitr() into serial_putc() Masahiro Yamada 0 siblings, 2 replies; 7+ messages in thread From: Masahiro Yamada @ 2015-10-24 4:17 UTC (permalink / raw) To: linux-serial Cc: Masahiro Yamada, Vineet Gupta, Kevin Cernekee, Jiri Slaby, Rob Herring, Peter Hurley, linux-kernel, Wang Long, Greg Kroah-Hartman Changes in v2: - split into two patches Masahiro Yamada (2): serial: 8250_early: do not save and restore IER in write callback serial: 8250_early: squash wait_for_xmitr() into serial_putc() drivers/tty/serial/8250/8250_early.c | 20 ++------------------ 1 file changed, 2 insertions(+), 18 deletions(-) -- 1.9.1 ^ permalink raw reply [flat|nested] 7+ messages in thread
* [PATCH v2 1/2] serial: 8250_early: do not save and restore IER in write callback 2015-10-24 4:17 [PATCH v2 0/2] serial: 8250_early: simplify serial_putc() Masahiro Yamada @ 2015-10-24 4:17 ` Masahiro Yamada 2015-10-27 13:54 ` Peter Hurley 2015-10-24 4:17 ` [PATCH v2 2/2] serial: 8250_early: squash wait_for_xmitr() into serial_putc() Masahiro Yamada 1 sibling, 1 reply; 7+ messages in thread From: Masahiro Yamada @ 2015-10-24 4:17 UTC (permalink / raw) To: linux-serial Cc: Masahiro Yamada, Vineet Gupta, Kevin Cernekee, Jiri Slaby, Rob Herring, Peter Hurley, linux-kernel, Greg Kroah-Hartman The IER has already been masked in early_serial8250_setup(), there is no reason to save and restore it every time early_serial8250_write() is called. Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com> --- drivers/tty/serial/8250/8250_early.c | 12 ------------ 1 file changed, 12 deletions(-) diff --git a/drivers/tty/serial/8250/8250_early.c b/drivers/tty/serial/8250/8250_early.c index 7aff3d8..559b681 100644 --- a/drivers/tty/serial/8250/8250_early.c +++ b/drivers/tty/serial/8250/8250_early.c @@ -99,20 +99,8 @@ static void __init early_serial8250_write(struct console *console, { struct earlycon_device *device = console->data; struct uart_port *port = &device->port; - unsigned int ier; - - /* Save the IER and disable interrupts preserving the UUE bit */ - ier = serial8250_early_in(port, UART_IER); - if (ier) - serial8250_early_out(port, UART_IER, ier & UART_IER_UUE); uart_console_write(port, s, count, serial_putc); - - /* Wait for transmitter to become empty and restore the IER */ - wait_for_xmitr(port); - - if (ier) - serial8250_early_out(port, UART_IER, ier); } static void __init init_port(struct earlycon_device *device) -- 1.9.1 ^ permalink raw reply related [flat|nested] 7+ messages in thread
* Re: [PATCH v2 1/2] serial: 8250_early: do not save and restore IER in write callback 2015-10-24 4:17 ` [PATCH v2 1/2] serial: 8250_early: do not save and restore IER in write callback Masahiro Yamada @ 2015-10-27 13:54 ` Peter Hurley 2015-10-28 3:27 ` Masahiro Yamada 0 siblings, 1 reply; 7+ messages in thread From: Peter Hurley @ 2015-10-27 13:54 UTC (permalink / raw) To: Masahiro Yamada, linux-serial Cc: Vineet Gupta, Kevin Cernekee, Jiri Slaby, Rob Herring, linux-kernel, Greg Kroah-Hartman Hi Masahiro, On 10/24/2015 12:17 AM, Masahiro Yamada wrote: > The IER has already been masked in early_serial8250_setup(), there is > no reason to save and restore it every time early_serial8250_write() > is called. > > Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com> > --- > > drivers/tty/serial/8250/8250_early.c | 12 ------------ > 1 file changed, 12 deletions(-) > > diff --git a/drivers/tty/serial/8250/8250_early.c b/drivers/tty/serial/8250/8250_early.c > index 7aff3d8..559b681 100644 > --- a/drivers/tty/serial/8250/8250_early.c > +++ b/drivers/tty/serial/8250/8250_early.c > @@ -99,20 +99,8 @@ static void __init early_serial8250_write(struct console *console, > { > struct earlycon_device *device = console->data; > struct uart_port *port = &device->port; > - unsigned int ier; > - > - /* Save the IER and disable interrupts preserving the UUE bit */ > - ier = serial8250_early_in(port, UART_IER); > - if (ier) > - serial8250_early_out(port, UART_IER, ier & UART_IER_UUE); > > uart_console_write(port, s, count, serial_putc); > - > - /* Wait for transmitter to become empty and restore the IER */ > - wait_for_xmitr(port); This wait_for_xmitr() change needs to be in patch 2/2. Regards, Peter Hurley > - > - if (ier) > - serial8250_early_out(port, UART_IER, ier); > } > > static void __init init_port(struct earlycon_device *device) > ^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [PATCH v2 1/2] serial: 8250_early: do not save and restore IER in write callback 2015-10-27 13:54 ` Peter Hurley @ 2015-10-28 3:27 ` Masahiro Yamada 2015-10-28 14:36 ` Peter Hurley 0 siblings, 1 reply; 7+ messages in thread From: Masahiro Yamada @ 2015-10-28 3:27 UTC (permalink / raw) To: Peter Hurley Cc: linux-serial, Vineet Gupta, Kevin Cernekee, Jiri Slaby, Rob Herring, Linux Kernel Mailing List, Greg Kroah-Hartman Hi Peter, 2015-10-27 22:54 GMT+09:00 Peter Hurley <peter@hurleysoftware.com>: > Hi Masahiro, > > On 10/24/2015 12:17 AM, Masahiro Yamada wrote: >> The IER has already been masked in early_serial8250_setup(), there is >> no reason to save and restore it every time early_serial8250_write() >> is called. >> >> Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com> >> --- >> >> drivers/tty/serial/8250/8250_early.c | 12 ------------ >> 1 file changed, 12 deletions(-) >> >> diff --git a/drivers/tty/serial/8250/8250_early.c b/drivers/tty/serial/8250/8250_early.c >> index 7aff3d8..559b681 100644 >> --- a/drivers/tty/serial/8250/8250_early.c >> +++ b/drivers/tty/serial/8250/8250_early.c >> @@ -99,20 +99,8 @@ static void __init early_serial8250_write(struct console *console, >> { >> struct earlycon_device *device = console->data; >> struct uart_port *port = &device->port; >> - unsigned int ier; >> - >> - /* Save the IER and disable interrupts preserving the UUE bit */ >> - ier = serial8250_early_in(port, UART_IER); >> - if (ier) >> - serial8250_early_out(port, UART_IER, ier & UART_IER_UUE); >> >> uart_console_write(port, s, count, serial_putc); > > > >> - >> - /* Wait for transmitter to become empty and restore the IER */ >> - wait_for_xmitr(port); > > This wait_for_xmitr() change needs to be in patch 2/2. > Why? We no longer restore the IER. We no longer have to wait here, either. -- Best Regards Masahiro Yamada ^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [PATCH v2 1/2] serial: 8250_early: do not save and restore IER in write callback 2015-10-28 3:27 ` Masahiro Yamada @ 2015-10-28 14:36 ` Peter Hurley 2015-10-29 5:21 ` Masahiro Yamada 0 siblings, 1 reply; 7+ messages in thread From: Peter Hurley @ 2015-10-28 14:36 UTC (permalink / raw) To: Masahiro Yamada Cc: linux-serial, Vineet Gupta, Kevin Cernekee, Jiri Slaby, Rob Herring, Linux Kernel Mailing List, Greg Kroah-Hartman On 10/27/2015 11:27 PM, Masahiro Yamada wrote: > Hi Peter, > > 2015-10-27 22:54 GMT+09:00 Peter Hurley <peter@hurleysoftware.com>: >> Hi Masahiro, >> >> On 10/24/2015 12:17 AM, Masahiro Yamada wrote: >>> The IER has already been masked in early_serial8250_setup(), there is >>> no reason to save and restore it every time early_serial8250_write() >>> is called. >>> >>> Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com> >>> --- >>> >>> drivers/tty/serial/8250/8250_early.c | 12 ------------ >>> 1 file changed, 12 deletions(-) >>> >>> diff --git a/drivers/tty/serial/8250/8250_early.c b/drivers/tty/serial/8250/8250_early.c >>> index 7aff3d8..559b681 100644 >>> --- a/drivers/tty/serial/8250/8250_early.c >>> +++ b/drivers/tty/serial/8250/8250_early.c >>> @@ -99,20 +99,8 @@ static void __init early_serial8250_write(struct console *console, >>> { >>> struct earlycon_device *device = console->data; >>> struct uart_port *port = &device->port; >>> - unsigned int ier; >>> - >>> - /* Save the IER and disable interrupts preserving the UUE bit */ >>> - ier = serial8250_early_in(port, UART_IER); >>> - if (ier) >>> - serial8250_early_out(port, UART_IER, ier & UART_IER_UUE); >>> >>> uart_console_write(port, s, count, serial_putc); >> >> >> >>> - >>> - /* Wait for transmitter to become empty and restore the IER */ >>> - wait_for_xmitr(port); >> >> This wait_for_xmitr() change needs to be in patch 2/2. >> > > > Why? Because if someone reports a regression bisected to this commit, we won't know if the regression is because we're not saving/restoring IER or because the transmitter is still running. Regards, Peter Hurley ^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [PATCH v2 1/2] serial: 8250_early: do not save and restore IER in write callback 2015-10-28 14:36 ` Peter Hurley @ 2015-10-29 5:21 ` Masahiro Yamada 0 siblings, 0 replies; 7+ messages in thread From: Masahiro Yamada @ 2015-10-29 5:21 UTC (permalink / raw) To: Peter Hurley Cc: linux-serial, Vineet Gupta, Kevin Cernekee, Jiri Slaby, Rob Herring, Linux Kernel Mailing List, Greg Kroah-Hartman 2015-10-28 23:36 GMT+09:00 Peter Hurley <peter@hurleysoftware.com>: > On 10/27/2015 11:27 PM, Masahiro Yamada wrote: >> Hi Peter, >> >> 2015-10-27 22:54 GMT+09:00 Peter Hurley <peter@hurleysoftware.com>: >>> Hi Masahiro, >>> >>> On 10/24/2015 12:17 AM, Masahiro Yamada wrote: >>>> The IER has already been masked in early_serial8250_setup(), there is >>>> no reason to save and restore it every time early_serial8250_write() >>>> is called. >>>> >>>> Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com> >>>> --- >>>> >>>> drivers/tty/serial/8250/8250_early.c | 12 ------------ >>>> 1 file changed, 12 deletions(-) >>>> >>>> diff --git a/drivers/tty/serial/8250/8250_early.c b/drivers/tty/serial/8250/8250_early.c >>>> index 7aff3d8..559b681 100644 >>>> --- a/drivers/tty/serial/8250/8250_early.c >>>> +++ b/drivers/tty/serial/8250/8250_early.c >>>> @@ -99,20 +99,8 @@ static void __init early_serial8250_write(struct console *console, >>>> { >>>> struct earlycon_device *device = console->data; >>>> struct uart_port *port = &device->port; >>>> - unsigned int ier; >>>> - >>>> - /* Save the IER and disable interrupts preserving the UUE bit */ >>>> - ier = serial8250_early_in(port, UART_IER); >>>> - if (ier) >>>> - serial8250_early_out(port, UART_IER, ier & UART_IER_UUE); >>>> >>>> uart_console_write(port, s, count, serial_putc); >>> >>> >>> >>>> - >>>> - /* Wait for transmitter to become empty and restore the IER */ >>>> - wait_for_xmitr(port); >>> >>> This wait_for_xmitr() change needs to be in patch 2/2. >>> >> >> >> Why? > > Because if someone reports a regression bisected to this commit, > we won't know if the regression is because we're not saving/restoring IER > or because the transmitter is still running. > Good point. I will send v3. Thanks! -- Best Regards Masahiro Yamada ^ permalink raw reply [flat|nested] 7+ messages in thread
* [PATCH v2 2/2] serial: 8250_early: squash wait_for_xmitr() into serial_putc() 2015-10-24 4:17 [PATCH v2 0/2] serial: 8250_early: simplify serial_putc() Masahiro Yamada 2015-10-24 4:17 ` [PATCH v2 1/2] serial: 8250_early: do not save and restore IER in write callback Masahiro Yamada @ 2015-10-24 4:17 ` Masahiro Yamada 1 sibling, 0 replies; 7+ messages in thread From: Masahiro Yamada @ 2015-10-24 4:17 UTC (permalink / raw) To: linux-serial Cc: Masahiro Yamada, Vineet Gupta, Kevin Cernekee, Jiri Slaby, Rob Herring, Peter Hurley, linux-kernel, Wang Long, Greg Kroah-Hartman Now, wait_for_xmitr() is only called from serial_putc(), and both are short enough. They can be merged into a single function. Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com> --- drivers/tty/serial/8250/8250_early.c | 8 ++------ 1 file changed, 2 insertions(+), 6 deletions(-) diff --git a/drivers/tty/serial/8250/8250_early.c b/drivers/tty/serial/8250/8250_early.c index 559b681..19aca19 100644 --- a/drivers/tty/serial/8250/8250_early.c +++ b/drivers/tty/serial/8250/8250_early.c @@ -76,21 +76,17 @@ static void __init serial8250_early_out(struct uart_port *port, int offset, int #define BOTH_EMPTY (UART_LSR_TEMT | UART_LSR_THRE) -static void __init wait_for_xmitr(struct uart_port *port) +static void __init serial_putc(struct uart_port *port, int c) { unsigned int status; for (;;) { status = serial8250_early_in(port, UART_LSR); if ((status & BOTH_EMPTY) == BOTH_EMPTY) - return; + break; cpu_relax(); } -} -static void __init serial_putc(struct uart_port *port, int c) -{ - wait_for_xmitr(port); serial8250_early_out(port, UART_TX, c); } -- 1.9.1 ^ permalink raw reply related [flat|nested] 7+ messages in thread
end of thread, other threads:[~2015-10-29 5:21 UTC | newest] Thread overview: 7+ messages (download: mbox.gz / follow: Atom feed) -- links below jump to the message on this page -- 2015-10-24 4:17 [PATCH v2 0/2] serial: 8250_early: simplify serial_putc() Masahiro Yamada 2015-10-24 4:17 ` [PATCH v2 1/2] serial: 8250_early: do not save and restore IER in write callback Masahiro Yamada 2015-10-27 13:54 ` Peter Hurley 2015-10-28 3:27 ` Masahiro Yamada 2015-10-28 14:36 ` Peter Hurley 2015-10-29 5:21 ` Masahiro Yamada 2015-10-24 4:17 ` [PATCH v2 2/2] serial: 8250_early: squash wait_for_xmitr() into serial_putc() Masahiro Yamada
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