| Message ID | f976766cd499c8d7053a1f442aba1494b4d3314f.1522736996.git.sean.wang@mediatek.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
Hi Sean, > In order to open up the required power gate before any operation can be > effectively performed over the serial bus between CPU and serdev, it's > clearly essential to add common attach functions for PM domains to serdev > at the probe phase. > > Similarly, the relevant dettach function for the PM domains should be > properly and reversely added at the remove phase. > > Signed-off-by: Sean Wang <sean.wang@mediatek.com> > Cc: Rob Herring <robh@kernel.org> > Cc: Ulf Hansson <ulf.hansson@linaro.org> > Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> > Cc: Jiri Slaby <jslaby@suse.com> > Cc: linux-serial@vger.kernel.org > --- > drivers/tty/serdev/core.c | 14 +++++++++++++- > 1 file changed, 13 insertions(+), 1 deletion(-) > > diff --git a/drivers/tty/serdev/core.c b/drivers/tty/serdev/core.c > index df93b72..c93d8ee 100644 > --- a/drivers/tty/serdev/core.c > +++ b/drivers/tty/serdev/core.c > @@ -13,6 +13,7 @@ > #include <linux/module.h> > #include <linux/of.h> > #include <linux/of_device.h> > +#include <linux/pm_domain.h> > #include <linux/serdev.h> > #include <linux/slab.h> > > @@ -330,8 +331,16 @@ EXPORT_SYMBOL_GPL(serdev_device_set_tiocm); > static int serdev_drv_probe(struct device *dev) > { > const struct serdev_device_driver *sdrv = to_serdev_device_driver(dev->driver); > + int ret; > + > + ret = dev_pm_domain_attach(dev, true); > + if (ret != -EPROBE_DEFER) { > + ret = sdrv->probe(to_serdev_device(dev)); > + if (ret) > + dev_pm_domain_detach(dev, true); > + } so if this is deferred, when does the serdev device gets probed? > > - return sdrv->probe(to_serdev_device(dev)); > + return ret; > } > > static int serdev_drv_remove(struct device *dev) > @@ -339,6 +348,9 @@ static int serdev_drv_remove(struct device *dev) > const struct serdev_device_driver *sdrv = to_serdev_device_driver(dev->driver); > if (sdrv->remove) > sdrv->remove(to_serdev_device(dev)); > + > + dev_pm_domain_detach(dev, true); > + > return 0; > } Regards Marcel
On Tue, 2018-04-03 at 12:29 +0200, Marcel Holtmann wrote: > Hi Sean, > > > In order to open up the required power gate before any operation can be > > effectively performed over the serial bus between CPU and serdev, it's > > clearly essential to add common attach functions for PM domains to serdev > > at the probe phase. > > > > Similarly, the relevant dettach function for the PM domains should be > > properly and reversely added at the remove phase. > > > > Signed-off-by: Sean Wang <sean.wang@mediatek.com> > > Cc: Rob Herring <robh@kernel.org> > > Cc: Ulf Hansson <ulf.hansson@linaro.org> > > Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> > > Cc: Jiri Slaby <jslaby@suse.com> > > Cc: linux-serial@vger.kernel.org > > --- > > drivers/tty/serdev/core.c | 14 +++++++++++++- > > 1 file changed, 13 insertions(+), 1 deletion(-) > > > > diff --git a/drivers/tty/serdev/core.c b/drivers/tty/serdev/core.c > > index df93b72..c93d8ee 100644 > > --- a/drivers/tty/serdev/core.c > > +++ b/drivers/tty/serdev/core.c > > @@ -13,6 +13,7 @@ > > #include <linux/module.h> > > #include <linux/of.h> > > #include <linux/of_device.h> > > +#include <linux/pm_domain.h> > > #include <linux/serdev.h> > > #include <linux/slab.h> > > > > @@ -330,8 +331,16 @@ EXPORT_SYMBOL_GPL(serdev_device_set_tiocm); > > static int serdev_drv_probe(struct device *dev) > > { > > const struct serdev_device_driver *sdrv = to_serdev_device_driver(dev->driver); > > + int ret; > > + > > + ret = dev_pm_domain_attach(dev, true); > > + if (ret != -EPROBE_DEFER) { > > + ret = sdrv->probe(to_serdev_device(dev)); > > + if (ret) > > + dev_pm_domain_detach(dev, true); > > + } > > so if this is deferred, when does the serdev device gets probed? > driver probe deferral mechanism is supported in driver core deferred_probe_initcall makes sure that deferred probing is delayed until late_initcall time. Below is a few of word I got from drivers/base/core.c I thought it helps to understand the mechanism in complete picture * If a required resource is not available yet, a driver can request probing to be deferred by returning -EPROBE_DEFER from its probe hook. * A driver returning -EPROBE_DEFER causes the device to be added to the pending list. A successful driver probe will trigger moving all devices from the pending to the active list so that the workqueue will eventually retry them. > > > > - return sdrv->probe(to_serdev_device(dev)); > > + return ret; > > } > > > > static int serdev_drv_remove(struct device *dev) > > @@ -339,6 +348,9 @@ static int serdev_drv_remove(struct device *dev) > > const struct serdev_device_driver *sdrv = to_serdev_device_driver(dev->driver); > > if (sdrv->remove) > > sdrv->remove(to_serdev_device(dev)); > > + > > + dev_pm_domain_detach(dev, true); > > + > > return 0; > > } > > Regards > > Marcel >
diff --git a/drivers/tty/serdev/core.c b/drivers/tty/serdev/core.c index df93b72..c93d8ee 100644 --- a/drivers/tty/serdev/core.c +++ b/drivers/tty/serdev/core.c @@ -13,6 +13,7 @@ #include <linux/module.h> #include <linux/of.h> #include <linux/of_device.h> +#include <linux/pm_domain.h> #include <linux/serdev.h> #include <linux/slab.h> @@ -330,8 +331,16 @@ EXPORT_SYMBOL_GPL(serdev_device_set_tiocm); static int serdev_drv_probe(struct device *dev) { const struct serdev_device_driver *sdrv = to_serdev_device_driver(dev->driver); + int ret; + + ret = dev_pm_domain_attach(dev, true); + if (ret != -EPROBE_DEFER) { + ret = sdrv->probe(to_serdev_device(dev)); + if (ret) + dev_pm_domain_detach(dev, true); + } - return sdrv->probe(to_serdev_device(dev)); + return ret; } static int serdev_drv_remove(struct device *dev) @@ -339,6 +348,9 @@ static int serdev_drv_remove(struct device *dev) const struct serdev_device_driver *sdrv = to_serdev_device_driver(dev->driver); if (sdrv->remove) sdrv->remove(to_serdev_device(dev)); + + dev_pm_domain_detach(dev, true); + return 0; }