| Message ID | 1447958344-836-8-git-send-email-geert+renesas@glider.be (mailing list archive) |
|---|---|
| State | Superseded |
| Delegated to: | Geert Uytterhoeven |
| Headers | show |
Hi Geert, Thank for the patch. On Thursday 19 November 2015 19:38:46 Geert Uytterhoeven wrote: > Transfer clock cleanup handling to the core device management code. > > Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be> > --- > drivers/tty/serial/sh-sci.c | 8 +++----- > 1 file changed, 3 insertions(+), 5 deletions(-) > > diff --git a/drivers/tty/serial/sh-sci.c b/drivers/tty/serial/sh-sci.c > index cba51da604253db6..9442961a198378c7 100644 > --- a/drivers/tty/serial/sh-sci.c > +++ b/drivers/tty/serial/sh-sci.c > @@ -2216,7 +2216,7 @@ static struct uart_ops sci_uart_ops = { > static int sci_init_clocks(struct sci_port *sci_port, struct device *dev) > { > /* Get the SCI functional clock. It's called "fck" on ARM. */ > - sci_port->fclk = clk_get(dev, "fck"); > + sci_port->fclk = devm_clk_get(dev, "fck"); Have you tested what happens if you unbind the device from the driver while userspace has the serial port open ? > if (PTR_ERR(sci_port->fclk) == -EPROBE_DEFER) > return -EPROBE_DEFER; > if (!IS_ERR(sci_port->fclk)) > @@ -2226,7 +2226,7 @@ static int sci_init_clocks(struct sci_port *sci_port, > struct device *dev) * But it used to be called "sci_ick", and we need to > maintain DT * backward compatibility. > */ > - sci_port->fclk = clk_get(dev, "sci_ick"); > + sci_port->fclk = devm_clk_get(dev, "sci_ick"); > if (PTR_ERR(sci_port->fclk) == -EPROBE_DEFER) > return -EPROBE_DEFER; > if (!IS_ERR(sci_port->fclk)) > @@ -2236,7 +2236,7 @@ static int sci_init_clocks(struct sci_port *sci_port, > struct device *dev) * Not all SH platforms declare a clock lookup entry for > SCI devices, * in which case we need to get the global "peripheral_clk" > clock. */ > - sci_port->fclk = clk_get(dev, "peripheral_clk"); > + sci_port->fclk = devm_clk_get(dev, "peripheral_clk"); > if (!IS_ERR(sci_port->fclk)) > return 0; > > @@ -2395,8 +2395,6 @@ static int sci_init_single(struct platform_device > *dev, > > static void sci_cleanup_single(struct sci_port *port) > { > - clk_put(port->fclk); > - > pm_runtime_disable(port->port.dev); > }
Hi Laurent, On Thu, Nov 19, 2015 at 9:38 PM, Laurent Pinchart <laurent.pinchart@ideasonboard.com> wrote: > On Thursday 19 November 2015 19:38:46 Geert Uytterhoeven wrote: >> Transfer clock cleanup handling to the core device management code. >> >> Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be> >> --- >> drivers/tty/serial/sh-sci.c | 8 +++----- >> 1 file changed, 3 insertions(+), 5 deletions(-) >> >> diff --git a/drivers/tty/serial/sh-sci.c b/drivers/tty/serial/sh-sci.c >> index cba51da604253db6..9442961a198378c7 100644 >> --- a/drivers/tty/serial/sh-sci.c >> +++ b/drivers/tty/serial/sh-sci.c >> @@ -2216,7 +2216,7 @@ static struct uart_ops sci_uart_ops = { >> static int sci_init_clocks(struct sci_port *sci_port, struct device *dev) >> { >> /* Get the SCI functional clock. It's called "fck" on ARM. */ >> - sci_port->fclk = clk_get(dev, "fck"); >> + sci_port->fclk = devm_clk_get(dev, "fck"); > > Have you tested what happens if you unbind the device from the driver while > userspace has the serial port open ? Yes I have. And I didn't notice any user-visible behavioral differences. There is a small ordering difference, though: with clk_get() and clk_put(), the explicit clk_put() is done before removing the device from its PM Domain (which involces another call to clk_put() on the module clock): device_release_driver __device_release_driver platform_drv_remove sci_remove sci_cleanup_single __clk_put genpd_dev_pm_detach pm_genpd_remove_device pm_clk_destroy __pm_clk_remove __clk_put When using devm_clk_get(), the managed cleanup is done after the device has been removed from its PM Domain: device_release_driver __device_release_driver platform_drv_remove genpd_dev_pm_detach pm_genpd_remove_device pm_clk_destroy __pm_clk_remove __clk_put release_nodes __clk_put This shouldn't make a difference, and applies to all other drivers using devm_*(), and devices that are part of a PM Domain. Gr{oetje,eeting}s, Geert -- Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org In personal conversations with technical people, I call myself a hacker. But when I'm talking to journalists I just say "programmer" or something like that. -- Linus Torvalds -- To unsubscribe from this list: send the line "unsubscribe linux-sh" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Hi Geert, On Thursday 10 December 2015 13:30:18 Geert Uytterhoeven wrote: > On Thu, Nov 19, 2015 at 9:38 PM, Laurent Pinchart wrote: > > On Thursday 19 November 2015 19:38:46 Geert Uytterhoeven wrote: > >> Transfer clock cleanup handling to the core device management code. > >> > >> Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be> > >> --- > >> > >> drivers/tty/serial/sh-sci.c | 8 +++----- > >> 1 file changed, 3 insertions(+), 5 deletions(-) > >> > >> diff --git a/drivers/tty/serial/sh-sci.c b/drivers/tty/serial/sh-sci.c > >> index cba51da604253db6..9442961a198378c7 100644 > >> --- a/drivers/tty/serial/sh-sci.c > >> +++ b/drivers/tty/serial/sh-sci.c > >> @@ -2216,7 +2216,7 @@ static struct uart_ops sci_uart_ops = { > >> > >> static int sci_init_clocks(struct sci_port *sci_port, struct device > >> *dev) > >> { > >> > >> /* Get the SCI functional clock. It's called "fck" on ARM. */ > >> > >> - sci_port->fclk = clk_get(dev, "fck"); > >> + sci_port->fclk = devm_clk_get(dev, "fck"); > > > > Have you tested what happens if you unbind the device from the driver > > while userspace has the serial port open ? > > Yes I have. And I didn't notice any user-visible behavioral differences. > > There is a small ordering difference, though: with clk_get() and clk_put(), > the explicit clk_put() is done before removing the device from its PM > Domain (which involces another call to clk_put() on the module clock): > > device_release_driver > __device_release_driver > platform_drv_remove > sci_remove > sci_cleanup_single > __clk_put > genpd_dev_pm_detach > pm_genpd_remove_device > pm_clk_destroy > __pm_clk_remove > __clk_put > > When using devm_clk_get(), the managed cleanup is done after the device has > been removed from its PM Domain: > > device_release_driver > __device_release_driver > platform_drv_remove > genpd_dev_pm_detach > pm_genpd_remove_device > pm_clk_destroy > __pm_clk_remove > __clk_put > release_nodes > __clk_put > > This shouldn't make a difference, and applies to all other drivers using > devm_*(), and devices that are part of a PM Domain. I was more concerned about the clk_disable_unprepare() calls. The function is called through the uart pm handler which is called when closing the uart (uart_close()). It's a bit difficult to follow the dynamic code paths as I'm not very familiar with the framework, but I was concerned that the would end up calling clk_disable_unprepare() on a clock for which we have no reference anymore. What prevents clk_disable_unprepare() from being called in the close path after the device has been unbound ? And what ensures that the clocks get unprepared when unbinding the device if the port is held open by a userspace process ?
Hi Laurent, On Sun, Dec 13, 2015 at 8:39 PM, Laurent Pinchart <laurent.pinchart@ideasonboard.com> wrote: > On Thursday 10 December 2015 13:30:18 Geert Uytterhoeven wrote: >> On Thu, Nov 19, 2015 at 9:38 PM, Laurent Pinchart wrote: >> > On Thursday 19 November 2015 19:38:46 Geert Uytterhoeven wrote: >> >> Transfer clock cleanup handling to the core device management code. >> >> >> >> Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be> >> >> --- >> >> >> >> drivers/tty/serial/sh-sci.c | 8 +++----- >> >> 1 file changed, 3 insertions(+), 5 deletions(-) >> >> >> >> diff --git a/drivers/tty/serial/sh-sci.c b/drivers/tty/serial/sh-sci.c >> >> index cba51da604253db6..9442961a198378c7 100644 >> >> --- a/drivers/tty/serial/sh-sci.c >> >> +++ b/drivers/tty/serial/sh-sci.c >> >> @@ -2216,7 +2216,7 @@ static struct uart_ops sci_uart_ops = { >> >> >> >> static int sci_init_clocks(struct sci_port *sci_port, struct device >> >> *dev) >> >> { >> >> >> >> /* Get the SCI functional clock. It's called "fck" on ARM. */ >> >> >> >> - sci_port->fclk = clk_get(dev, "fck"); >> >> + sci_port->fclk = devm_clk_get(dev, "fck"); >> > >> > Have you tested what happens if you unbind the device from the driver >> > while userspace has the serial port open ? >> >> Yes I have. And I didn't notice any user-visible behavioral differences. >> >> There is a small ordering difference, though: with clk_get() and clk_put(), >> the explicit clk_put() is done before removing the device from its PM >> Domain (which involces another call to clk_put() on the module clock): >> >> device_release_driver >> __device_release_driver >> platform_drv_remove >> sci_remove >> sci_cleanup_single >> __clk_put >> genpd_dev_pm_detach >> pm_genpd_remove_device >> pm_clk_destroy >> __pm_clk_remove >> __clk_put >> >> When using devm_clk_get(), the managed cleanup is done after the device has >> been removed from its PM Domain: >> >> device_release_driver >> __device_release_driver >> platform_drv_remove >> genpd_dev_pm_detach >> pm_genpd_remove_device >> pm_clk_destroy >> __pm_clk_remove >> __clk_put >> release_nodes >> __clk_put >> >> This shouldn't make a difference, and applies to all other drivers using >> devm_*(), and devices that are part of a PM Domain. > > I was more concerned about the clk_disable_unprepare() calls. The function is > called through the uart pm handler which is called when closing the uart > (uart_close()). It's a bit difficult to follow the dynamic code paths as I'm > not very familiar with the framework, but I was concerned that the would end > up calling clk_disable_unprepare() on a clock for which we have no reference > anymore. What prevents clk_disable_unprepare() from being called in the close > path after the device has been unbound ? And what ensures that the clocks get > unprepared when unbinding the device if the port is held open by a userspace > process ? Both questions are answered by uart_hangup(): - uart_hangup() sets port->count to zero, hence uart_close() returns early (second return statement), long before it would call the uart pm handler. - uart_hangup() calls uart_change_pm(state, UART_PM_STATE_OFF); Gr{oetje,eeting}s, Geert -- Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org In personal conversations with technical people, I call myself a hacker. But when I'm talking to journalists I just say "programmer" or something like that. -- Linus Torvalds -- To unsubscribe from this list: send the line "unsubscribe linux-sh" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Hi Geert, On Monday 14 December 2015 11:34:11 Geert Uytterhoeven wrote: > On Sun, Dec 13, 2015 at 8:39 PM, Laurent Pinchart wrote: > > On Thursday 10 December 2015 13:30:18 Geert Uytterhoeven wrote: > >> On Thu, Nov 19, 2015 at 9:38 PM, Laurent Pinchart wrote: > >> > On Thursday 19 November 2015 19:38:46 Geert Uytterhoeven wrote: > >> >> Transfer clock cleanup handling to the core device management code. > >> >> > >> >> Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be> > >> >> --- > >> >> > >> >> drivers/tty/serial/sh-sci.c | 8 +++----- > >> >> 1 file changed, 3 insertions(+), 5 deletions(-) > >> >> > >> >> diff --git a/drivers/tty/serial/sh-sci.c b/drivers/tty/serial/sh-sci.c > >> >> index cba51da604253db6..9442961a198378c7 100644 > >> >> --- a/drivers/tty/serial/sh-sci.c > >> >> +++ b/drivers/tty/serial/sh-sci.c > >> >> @@ -2216,7 +2216,7 @@ static struct uart_ops sci_uart_ops = { > >> >> > >> >> static int sci_init_clocks(struct sci_port *sci_port, struct device > >> >> *dev) > >> >> { > >> >> /* Get the SCI functional clock. It's called "fck" on ARM. */ > >> >> - sci_port->fclk = clk_get(dev, "fck"); > >> >> + sci_port->fclk = devm_clk_get(dev, "fck"); > >> > > >> > Have you tested what happens if you unbind the device from the driver > >> > while userspace has the serial port open ? > >> > >> Yes I have. And I didn't notice any user-visible behavioral differences. > >> > >> There is a small ordering difference, though: with clk_get() and > >> clk_put(), the explicit clk_put() is done before removing the device from > >> its PM > >> > >> Domain (which involces another call to clk_put() on the module clock): > >> device_release_driver > >> __device_release_driver > >> platform_drv_remove > >> sci_remove > >> sci_cleanup_single > >> __clk_put > >> genpd_dev_pm_detach > >> pm_genpd_remove_device > >> pm_clk_destroy > >> __pm_clk_remove > >> __clk_put > >> > >> When using devm_clk_get(), the managed cleanup is done after the device > >> has been removed from its PM Domain: > >> device_release_driver > >> __device_release_driver > >> platform_drv_remove > >> genpd_dev_pm_detach > >> pm_genpd_remove_device > >> pm_clk_destroy > >> __pm_clk_remove > >> __clk_put > >> release_nodes > >> __clk_put > >> > >> This shouldn't make a difference, and applies to all other drivers using > >> devm_*(), and devices that are part of a PM Domain. > > > > I was more concerned about the clk_disable_unprepare() calls. The function > > is called through the uart pm handler which is called when closing the > > uart (uart_close()). It's a bit difficult to follow the dynamic code > > paths as I'm not very familiar with the framework, but I was concerned > > that the would end up calling clk_disable_unprepare() on a clock for > > which we have no reference anymore. What prevents clk_disable_unprepare() > > from being called in the close path after the device has been unbound ? > > And what ensures that the clocks get unprepared when unbinding the device > > if the port is held open by a userspace process ? > > Both questions are answered by uart_hangup(): > - uart_hangup() sets port->count to zero, hence uart_close() returns early > (second return statement), long before it would call the uart pm handler. > - uart_hangup() calls uart_change_pm(state, UART_PM_STATE_OFF); Thank you for making me slightly wiser :-)
diff --git a/drivers/tty/serial/sh-sci.c b/drivers/tty/serial/sh-sci.c index cba51da604253db6..9442961a198378c7 100644 --- a/drivers/tty/serial/sh-sci.c +++ b/drivers/tty/serial/sh-sci.c @@ -2216,7 +2216,7 @@ static struct uart_ops sci_uart_ops = { static int sci_init_clocks(struct sci_port *sci_port, struct device *dev) { /* Get the SCI functional clock. It's called "fck" on ARM. */ - sci_port->fclk = clk_get(dev, "fck"); + sci_port->fclk = devm_clk_get(dev, "fck"); if (PTR_ERR(sci_port->fclk) == -EPROBE_DEFER) return -EPROBE_DEFER; if (!IS_ERR(sci_port->fclk)) @@ -2226,7 +2226,7 @@ static int sci_init_clocks(struct sci_port *sci_port, struct device *dev) * But it used to be called "sci_ick", and we need to maintain DT * backward compatibility. */ - sci_port->fclk = clk_get(dev, "sci_ick"); + sci_port->fclk = devm_clk_get(dev, "sci_ick"); if (PTR_ERR(sci_port->fclk) == -EPROBE_DEFER) return -EPROBE_DEFER; if (!IS_ERR(sci_port->fclk)) @@ -2236,7 +2236,7 @@ static int sci_init_clocks(struct sci_port *sci_port, struct device *dev) * Not all SH platforms declare a clock lookup entry for SCI devices, * in which case we need to get the global "peripheral_clk" clock. */ - sci_port->fclk = clk_get(dev, "peripheral_clk"); + sci_port->fclk = devm_clk_get(dev, "peripheral_clk"); if (!IS_ERR(sci_port->fclk)) return 0; @@ -2395,8 +2395,6 @@ static int sci_init_single(struct platform_device *dev, static void sci_cleanup_single(struct sci_port *port) { - clk_put(port->fclk); - pm_runtime_disable(port->port.dev); }
Transfer clock cleanup handling to the core device management code. Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be> --- drivers/tty/serial/sh-sci.c | 8 +++----- 1 file changed, 3 insertions(+), 5 deletions(-)