Re: [PATCH v3 1/2] drivers: bus: simple-pm-bus: Add support for probing simple bus only devices

Saravana Kannan
2021-09-08T22:03:00Z

On Tue, Sep 7, 2021 at 3:41 AM Ulf Hansson <ulf.hansson@linaro.org> wrote:
>
> On Sat, 4 Sept 2021 at 02:05, Saravana Kannan <saravanak@google.com> wrote:
> >
> > fw_devlink could end up creating device links for bus only devices.
> > However, bus only devices don't get probed and can block probe() or
> > sync_state() [1] call backs of other devices. To avoid this, probe these
> > devices using the simple-pm-bus driver.
> >
> > However, there are instances of devices that are not simple buses (they
> > get probed by their specific drivers) that also list the "simple-bus"
> > (or other bus only compatible strings) in their compatible property to
> > automatically populate their child devices. We still want these devices
> > to get probed by their specific drivers. So, we make sure this driver
> > only probes devices that are only buses.
> >
> > [1] - https://lore.kernel.org/lkml/CAPDyKFo9Bxremkb1dDrr4OcXSpE0keVze94Cm=zrkOVxHHxBmQ@mail.gmail.com/
> > Signed-off-by: Saravana Kannan <saravanak@google.com>
> > Tested-by: Saravana Kannan <saravanak@google.com>
>
> Reviewed-by: Ulf Hansson <ulf.hansson@linaro.org>
>
> I will run some tests as soon as I can and let you know the results.

Thanks.

-Saravana

>
> Kind regards
> Uffe
>
> > ---
> > drivers/bus/simple-pm-bus.c | 32 +++++++++++++++++++++++++++++---
> > 1 file changed, 29 insertions(+), 3 deletions(-)
> >
> > diff --git a/drivers/bus/simple-pm-bus.c b/drivers/bus/simple-pm-bus.c
> > index 01a3d0cd08ed..3e086a9f34cb 100644
> > --- a/drivers/bus/simple-pm-bus.c
> > +++ b/drivers/bus/simple-pm-bus.c
> > @@ -13,11 +13,26 @@
> > #include <linux/platform_device.h>
> > #include <linux/pm_runtime.h>
> >
> > -
> > static int simple_pm_bus_probe(struct platform_device *pdev)
> > {
> > - const struct of_dev_auxdata *lookup = dev_get_platdata(&pdev->dev);
> > - struct device_node *np = pdev->dev.of_node;
> > + const struct device *dev = &pdev->dev;
> > + const struct of_dev_auxdata *lookup = dev_get_platdata(dev);
> > + struct device_node *np = dev->of_node;
> > + const struct of_device_id *match;
> > +
> > + match = of_match_device(dev->driver->of_match_table, dev);
> > +
> > + /*
> > + * These are transparent bus devices (not simple-pm-bus matches) that
> > + * have their child nodes populated automatically. So, don't need to
> > + * do anything more.
> > + */
> > + if (match && match->data) {
> > + if (of_property_match_string(np, "compatible", match->compatible) == 0)
> > + return 0;
> > + else
> > + return -ENODEV;
> > + }
> >
> > dev_dbg(&pdev->dev, "%s\n", __func__);
> >
> > @@ -31,14 +46,25 @@ static int simple_pm_bus_probe(struct platform_device *pdev)
> >
> > static int simple_pm_bus_remove(struct platform_device *pdev)
> > {
> > + const void *data = of_device_get_match_data(&pdev->dev);
> > +
> > + if (data)
> > + return 0;
> > +
> > dev_dbg(&pdev->dev, "%s\n", __func__);
> >
> > pm_runtime_disable(&pdev->dev);
> > return 0;
> > }
> >
> > +#define ONLY_BUS ((void *) 1) /* Match if the device is only a bus. */
> > +
> > static const struct of_device_id simple_pm_bus_of_match[] = {
> > { .compatible = "simple-pm-bus", },
> > + { .compatible = "simple-bus", .data = ONLY_BUS },
> > + { .compatible = "simple-mfd", .data = ONLY_BUS },
> > + { .compatible = "isa", .data = ONLY_BUS },
> > + { .compatible = "arm,amba-bus", .data = ONLY_BUS },
> > { /* sentinel */ }
> > };
> > MODULE_DEVICE_TABLE(of, simple_pm_bus_of_match);
> > --
> > 2.33.0.153.gba50c8fa24-goog
> >