* [PATCH] serial: 8250_early: do not save and restore IER in write callback
@ 2015-10-22 8:21 Masahiro Yamada
2015-10-23 12:45 ` Peter Hurley
0 siblings, 1 reply; 3+ messages in thread
From: Masahiro Yamada @ 2015-10-22 8:21 UTC (permalink / raw)
To: linux-serial
Cc: Masahiro Yamada, Vineet Gupta, Kevin Cernekee, Jiri Slaby,
Rob Herring, Peter Hurley, linux-kernel, Eddie Huang,
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.
Let wait_for_xmitr() melt into serial_putc().
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
---
drivers/tty/serial/8250/8250_early.c | 20 ++------------------
1 file changed, 2 insertions(+), 18 deletions(-)
diff --git a/drivers/tty/serial/8250/8250_early.c b/drivers/tty/serial/8250/8250_early.c
index 7aff3d8..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);
}
@@ -99,20 +95,8 @@ 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] 3+ messages in thread* Re: [PATCH] serial: 8250_early: do not save and restore IER in write callback
2015-10-22 8:21 [PATCH] serial: 8250_early: do not save and restore IER in write callback Masahiro Yamada
@ 2015-10-23 12:45 ` Peter Hurley
2015-10-24 4:02 ` Masahiro Yamada
0 siblings, 1 reply; 3+ messages in thread
From: Peter Hurley @ 2015-10-23 12:45 UTC (permalink / raw)
To: Masahiro Yamada, linux-serial
Cc: Vineet Gupta, Kevin Cernekee, Jiri Slaby, Rob Herring,
linux-kernel, Eddie Huang, Greg Kroah-Hartman
On 10/22/2015 04:21 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.
>
> Let wait_for_xmitr() melt into serial_putc().
Both of these changes are ok with me, but please split this into
2 patches so reverting either one in case of regression is trivial.
Regards,
Peter Hurley
> Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
> ---
>
> drivers/tty/serial/8250/8250_early.c | 20 ++------------------
> 1 file changed, 2 insertions(+), 18 deletions(-)
>
> diff --git a/drivers/tty/serial/8250/8250_early.c b/drivers/tty/serial/8250/8250_early.c
> index 7aff3d8..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);
> }
>
> @@ -99,20 +95,8 @@ 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)
>
^ permalink raw reply [flat|nested] 3+ messages in thread* Re: [PATCH] serial: 8250_early: do not save and restore IER in write callback
2015-10-23 12:45 ` Peter Hurley
@ 2015-10-24 4:02 ` Masahiro Yamada
0 siblings, 0 replies; 3+ messages in thread
From: Masahiro Yamada @ 2015-10-24 4:02 UTC (permalink / raw)
To: Peter Hurley
Cc: linux-serial, Vineet Gupta, Kevin Cernekee, Jiri Slaby,
Rob Herring, Linux Kernel Mailing List, Eddie Huang,
Greg Kroah-Hartman
Hi Peter,
2015-10-23 21:45 GMT+09:00 Peter Hurley <peter@hurleysoftware.com>:
> On 10/22/2015 04:21 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.
>>
>> Let wait_for_xmitr() melt into serial_putc().
>
> Both of these changes are ok with me, but please split this into
> 2 patches so reverting either one in case of regression is trivial.
>
> Regards,
> Peter Hurley
OK, will do.
--
Best Regards
Masahiro Yamada
^ permalink raw reply [flat|nested] 3+ messages in thread
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2015-10-22 8:21 [PATCH] serial: 8250_early: do not save and restore IER in write callback Masahiro Yamada
2015-10-23 12:45 ` Peter Hurley
2015-10-24 4:02 ` Masahiro Yamada
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