| Message ID | 1418891601-53769-2-git-send-email-eddie.huang@mediatek.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
2014-12-18 9:33 GMT+01:00 Eddie Huang <eddie.huang@mediatek.com>: > Mediatek UART has highspeed register, but 8250_early.c doesn't > support this, so add earlycon in 8250_mtk.c > > Signed-off-by: Eddie Huang <eddie.huang@mediatek.com> > --- > drivers/tty/serial/8250/8250_mtk.c | 33 +++++++++++++++++++++++++++++++++ > 1 file changed, 33 insertions(+) > > diff --git a/drivers/tty/serial/8250/8250_mtk.c b/drivers/tty/serial/8250/8250_mtk.c > index de7aae5..65dd569 100644 > --- a/drivers/tty/serial/8250/8250_mtk.c > +++ b/drivers/tty/serial/8250/8250_mtk.c > @@ -23,6 +23,7 @@ > #include <linux/pm_runtime.h> > #include <linux/serial_8250.h> > #include <linux/serial_reg.h> > +#include <linux/console.h> > > #include "8250.h" > > @@ -289,6 +290,38 @@ static struct platform_driver mtk8250_platform_driver = { > }; > module_platform_driver(mtk8250_platform_driver); > > +#define BOTH_EMPTY (UART_LSR_TEMT | UART_LSR_THRE) > + > +static void __init mtk8250_serial_putc(struct uart_port *port, int c) > +{ > + while ((readl(port->membase + (UART_LSR << 2)) & BOTH_EMPTY) != > + BOTH_EMPTY) > + ; Please delete newline before the semicolon. > + writel(c, port->membase + (UART_TX << 2)); > +} > + > +static void __init early_mtk8250_write(struct console *console, > + const char *s, unsigned int count) > +{ > + struct earlycon_device *dev = console->data; > + > + uart_console_write(&dev->port, s, count, mtk8250_serial_putc); > +} > + > +static int __init early_mtk8250_setup(struct earlycon_device *device, > + const char *options) > +{ > + if (!device->port.membase) > + return -ENODEV; > + > + device->con->write = early_mtk8250_write; > + > + return 0; > +} > + > +EARLYCON_DECLARE(mtk8250, early_mtk8250_setup); > +OF_EARLYCON_DECLARE(mtk8250, "mediatek,mt6577-uart", early_mtk8250_setup); > + > MODULE_AUTHOR("Matthias Brugger"); > MODULE_LICENSE("GPL"); > MODULE_DESCRIPTION("Mediatek 8250 serial port driver"); > -- > 1.8.1.1.dirty >
On Thursday 18 December 2014 09:48:31 Matthias Brugger wrote: > > +static void __init mtk8250_serial_putc(struct uart_port *port, int c) > > +{ > > + while ((readl(port->membase + (UART_LSR << 2)) & BOTH_EMPTY) != > > + BOTH_EMPTY) > > + ; > > Please delete newline before the semicolon. > No, that newline is best kept in there for clarity. An even better way to write this would be using cpu_relax(): while ((readl(port->membase + (UART_LSR << 2)) & BOTH_EMPTY) != BOTH_EMPTY) cpu_relax(); which the kernel convention for doing busy-loops. Arnd
On Thu, Dec 18, 2014 at 2:33 AM, Eddie Huang <eddie.huang@mediatek.com> wrote: > Mediatek UART has highspeed register, but 8250_early.c doesn't > support this, so add earlycon in 8250_mtk.c I don't see any highspeed register setup here. More generically, aren't you just skipping any UART setup? That may be useful on other platforms with 8250s, too. With the kernel command line version, you could perhaps add a "noinit" flag. The DT case is harder, and I'm not sure how we should handle that. We could perhaps add a "stdout-path-initialized" flag to chosen. > > Signed-off-by: Eddie Huang <eddie.huang@mediatek.com> > --- > drivers/tty/serial/8250/8250_mtk.c | 33 +++++++++++++++++++++++++++++++++ > 1 file changed, 33 insertions(+) > > diff --git a/drivers/tty/serial/8250/8250_mtk.c b/drivers/tty/serial/8250/8250_mtk.c > index de7aae5..65dd569 100644 > --- a/drivers/tty/serial/8250/8250_mtk.c > +++ b/drivers/tty/serial/8250/8250_mtk.c > @@ -23,6 +23,7 @@ > #include <linux/pm_runtime.h> > #include <linux/serial_8250.h> > #include <linux/serial_reg.h> > +#include <linux/console.h> > > #include "8250.h" > > @@ -289,6 +290,38 @@ static struct platform_driver mtk8250_platform_driver = { > }; > module_platform_driver(mtk8250_platform_driver); > > +#define BOTH_EMPTY (UART_LSR_TEMT | UART_LSR_THRE) > + > +static void __init mtk8250_serial_putc(struct uart_port *port, int c) > +{ > + while ((readl(port->membase + (UART_LSR << 2)) & BOTH_EMPTY) != > + BOTH_EMPTY) > + ; > + writel(c, port->membase + (UART_TX << 2)); > +} > + > +static void __init early_mtk8250_write(struct console *console, > + const char *s, unsigned int count) Is there a reason early_serial8250_write can't work for you other than it is currently static? Rob > +{ > + struct earlycon_device *dev = console->data; > + > + uart_console_write(&dev->port, s, count, mtk8250_serial_putc); > +} > + > +static int __init early_mtk8250_setup(struct earlycon_device *device, > + const char *options) > +{ > + if (!device->port.membase) > + return -ENODEV; > + > + device->con->write = early_mtk8250_write; > + > + return 0; > +} > + > +EARLYCON_DECLARE(mtk8250, early_mtk8250_setup); > +OF_EARLYCON_DECLARE(mtk8250, "mediatek,mt6577-uart", early_mtk8250_setup); > + > MODULE_AUTHOR("Matthias Brugger"); > MODULE_LICENSE("GPL"); > MODULE_DESCRIPTION("Mediatek 8250 serial port driver"); > -- > 1.8.1.1.dirty >
Hi Rob, On Fri, 2014-12-26 at 15:24 -0600, Rob Herring wrote: > On Thu, Dec 18, 2014 at 2:33 AM, Eddie Huang <eddie.huang@mediatek.com> wrote: > > Mediatek UART has highspeed register, but 8250_early.c doesn't > > support this, so add earlycon in 8250_mtk.c > > I don't see any highspeed register setup here. More generically, > aren't you just skipping any UART setup? That may be useful on other > platforms with 8250s, too. With the kernel command line version, you > could perhaps add a "noinit" flag. The DT case is harder, and I'm not > sure how we should handle that. We could perhaps add a > "stdout-path-initialized" flag to chosen. > Yes, I skipped UART setup same as msm_serial.c and amba-pl011.c (although they are standalone serial driver). Just like earlyprintk, I think earlycon should reuse UART setting in loader. Since some other platforms with 8250 already depend on this, it's ok to add flags to distinguish whether 8250 earlycon driver should init hw or not. As you said, add "noinit" flag is simple, but "stdout-path-initialized" need more discussion. > > > > Signed-off-by: Eddie Huang <eddie.huang@mediatek.com> > > --- > > drivers/tty/serial/8250/8250_mtk.c | 33 +++++++++++++++++++++++++++++++++ > > 1 file changed, 33 insertions(+) > > > > diff --git a/drivers/tty/serial/8250/8250_mtk.c b/drivers/tty/serial/8250/8250_mtk.c > > index de7aae5..65dd569 100644 > > --- a/drivers/tty/serial/8250/8250_mtk.c > > +++ b/drivers/tty/serial/8250/8250_mtk.c > > @@ -23,6 +23,7 @@ > > #include <linux/pm_runtime.h> > > #include <linux/serial_8250.h> > > #include <linux/serial_reg.h> > > +#include <linux/console.h> > > > > #include "8250.h" > > > > @@ -289,6 +290,38 @@ static struct platform_driver mtk8250_platform_driver = { > > }; > > module_platform_driver(mtk8250_platform_driver); > > > > +#define BOTH_EMPTY (UART_LSR_TEMT | UART_LSR_THRE) > > + > > +static void __init mtk8250_serial_putc(struct uart_port *port, int c) > > +{ > > + while ((readl(port->membase + (UART_LSR << 2)) & BOTH_EMPTY) != > > + BOTH_EMPTY) > > + ; > > + writel(c, port->membase + (UART_TX << 2)); > > +} > > + > > +static void __init early_mtk8250_write(struct console *console, > > + const char *s, unsigned int count) > > Is there a reason early_serial8250_write can't work for you other than > it is currently static? > > Rob > The reason is only static. I want to keep 8250_early.c untouchable, all modifications in 8250_mtk.c
On Sun, Dec 28, 2014 at 10:24 PM, Eddie Huang <eddie.huang@mediatek.com> wrote: > Hi Rob, > > On Fri, 2014-12-26 at 15:24 -0600, Rob Herring wrote: >> On Thu, Dec 18, 2014 at 2:33 AM, Eddie Huang <eddie.huang@mediatek.com> wrote: >> > Mediatek UART has highspeed register, but 8250_early.c doesn't >> > support this, so add earlycon in 8250_mtk.c >> >> I don't see any highspeed register setup here. More generically, >> aren't you just skipping any UART setup? That may be useful on other >> platforms with 8250s, too. With the kernel command line version, you >> could perhaps add a "noinit" flag. The DT case is harder, and I'm not >> sure how we should handle that. We could perhaps add a >> "stdout-path-initialized" flag to chosen. >> > > Yes, I skipped UART setup same as msm_serial.c and amba-pl011.c > (although they are standalone serial driver). Just like earlyprintk, I > think earlycon should reuse UART setting in loader. Since some other > platforms with 8250 already depend on this, it's ok to add flags to > distinguish whether 8250 earlycon driver should init hw or not. As you > said, add "noinit" flag is simple, but "stdout-path-initialized" need > more discussion. > >> > >> > Signed-off-by: Eddie Huang <eddie.huang@mediatek.com> >> > --- >> > drivers/tty/serial/8250/8250_mtk.c | 33 +++++++++++++++++++++++++++++++++ >> > 1 file changed, 33 insertions(+) >> > >> > diff --git a/drivers/tty/serial/8250/8250_mtk.c b/drivers/tty/serial/8250/8250_mtk.c >> > index de7aae5..65dd569 100644 >> > --- a/drivers/tty/serial/8250/8250_mtk.c >> > +++ b/drivers/tty/serial/8250/8250_mtk.c >> > @@ -23,6 +23,7 @@ >> > #include <linux/pm_runtime.h> >> > #include <linux/serial_8250.h> >> > #include <linux/serial_reg.h> >> > +#include <linux/console.h> >> > >> > #include "8250.h" >> > >> > @@ -289,6 +290,38 @@ static struct platform_driver mtk8250_platform_driver = { >> > }; >> > module_platform_driver(mtk8250_platform_driver); >> > >> > +#define BOTH_EMPTY (UART_LSR_TEMT | UART_LSR_THRE) >> > + >> > +static void __init mtk8250_serial_putc(struct uart_port *port, int c) >> > +{ >> > + while ((readl(port->membase + (UART_LSR << 2)) & BOTH_EMPTY) != >> > + BOTH_EMPTY) >> > + ; >> > + writel(c, port->membase + (UART_TX << 2)); >> > +} >> > + >> > +static void __init early_mtk8250_write(struct console *console, >> > + const char *s, unsigned int count) >> >> Is there a reason early_serial8250_write can't work for you other than >> it is currently static? >> >> Rob >> > > The reason is only static. I want to keep 8250_early.c untouchable, all > modifications in 8250_mtk.c That is not how kernel development works. You should fix 8250_early.c to do what you need rather than duplicating code. Rob
On Monday 29 December 2014 12:24:56 Eddie Huang wrote: > Hi Rob, > > On Fri, 2014-12-26 at 15:24 -0600, Rob Herring wrote: > > On Thu, Dec 18, 2014 at 2:33 AM, Eddie Huang <eddie.huang@mediatek.com> wrote: > > > Mediatek UART has highspeed register, but 8250_early.c doesn't > > > support this, so add earlycon in 8250_mtk.c > > > > I don't see any highspeed register setup here. More generically, > > aren't you just skipping any UART setup? That may be useful on other > > platforms with 8250s, too. With the kernel command line version, you > > could perhaps add a "noinit" flag. The DT case is harder, and I'm not > > sure how we should handle that. We could perhaps add a > > "stdout-path-initialized" flag to chosen. > > > > Yes, I skipped UART setup same as msm_serial.c and amba-pl011.c > (although they are standalone serial driver). Just like earlyprintk, I > think earlycon should reuse UART setting in loader. Since some other > platforms with 8250 already depend on this, it's ok to add flags to > distinguish whether 8250 earlycon driver should init hw or not. As you > said, add "noinit" flag is simple, but "stdout-path-initialized" need > more discussion. It would definitely be nice to have consistent behavior, and I also think it would be good to default to noinit for the console, because that is the more likely case. Basically anything that can do debug_ll on ARM already depends on this behavior because the debug_ll infrastructure does not initialize the console before using it. I believe the same is true for powerpc udbg. Arnd
diff --git a/drivers/tty/serial/8250/8250_mtk.c b/drivers/tty/serial/8250/8250_mtk.c index de7aae5..65dd569 100644 --- a/drivers/tty/serial/8250/8250_mtk.c +++ b/drivers/tty/serial/8250/8250_mtk.c @@ -23,6 +23,7 @@ #include <linux/pm_runtime.h> #include <linux/serial_8250.h> #include <linux/serial_reg.h> +#include <linux/console.h> #include "8250.h" @@ -289,6 +290,38 @@ static struct platform_driver mtk8250_platform_driver = { }; module_platform_driver(mtk8250_platform_driver); +#define BOTH_EMPTY (UART_LSR_TEMT | UART_LSR_THRE) + +static void __init mtk8250_serial_putc(struct uart_port *port, int c) +{ + while ((readl(port->membase + (UART_LSR << 2)) & BOTH_EMPTY) != + BOTH_EMPTY) + ; + writel(c, port->membase + (UART_TX << 2)); +} + +static void __init early_mtk8250_write(struct console *console, + const char *s, unsigned int count) +{ + struct earlycon_device *dev = console->data; + + uart_console_write(&dev->port, s, count, mtk8250_serial_putc); +} + +static int __init early_mtk8250_setup(struct earlycon_device *device, + const char *options) +{ + if (!device->port.membase) + return -ENODEV; + + device->con->write = early_mtk8250_write; + + return 0; +} + +EARLYCON_DECLARE(mtk8250, early_mtk8250_setup); +OF_EARLYCON_DECLARE(mtk8250, "mediatek,mt6577-uart", early_mtk8250_setup); + MODULE_AUTHOR("Matthias Brugger"); MODULE_LICENSE("GPL"); MODULE_DESCRIPTION("Mediatek 8250 serial port driver");
Mediatek UART has highspeed register, but 8250_early.c doesn't support this, so add earlycon in 8250_mtk.c Signed-off-by: Eddie Huang <eddie.huang@mediatek.com> --- drivers/tty/serial/8250/8250_mtk.c | 33 +++++++++++++++++++++++++++++++++ 1 file changed, 33 insertions(+)