Hi Saravana, Thanks for your patch! CC linux-pm, Lee (mfd) On Sat, Sep 4, 2021 at 2:05 AM Saravana Kannan <saravanak@xxxxxxxxxx> 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. Note that this can also be the case for buses declaring compatibility with "simple-pm-bus". However, at the moment, none of such device nodes in upstream DTS files have device-specific drivers. > [1] - https://lore.kernel.org/lkml/CAPDyKFo9Bxremkb1dDrr4OcXSpE0keVze94Cm=zrkOVxHHxBmQ@xxxxxxxxxxxxxx/ > Signed-off-by: Saravana Kannan <saravanak@xxxxxxxxxx> > Tested-by: Saravana Kannan <saravanak@xxxxxxxxxx> > --- 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) Does this work as expected? Having multiple compatible values in a device node does not guarantee there exist a separate driver for any of the device-specific compatible values. > + return 0; > + else > + return -ENODEV; So if we get here, as both branches use "return", we skip the pm_runtime_enable() and of_platform_populate() below: - of_platform_populate() is handled for these buses by of_platform_default_populate(), so that's OK, - I'm wondering if any of the simple-mfd sub-devices use Runtime PM, but currently fail to save power because pm_runtime_enable() is never called for the MFD container, just like with simple-bus... > + } > > 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 }, #ifdef CONFIG_ARM_AMBA ? > + { .compatible = "arm,amba-bus", .data = ONLY_BUS }, > { /* sentinel */ } This is now (almost[*]) the same as of_default_bus_match_table[] in drivers/of/platform.c. Perhaps it can be shared? [*] Especially if "simple-pm-bus" and "simple-bus" would be treated the same. > }; > MODULE_DEVICE_TABLE(of, simple_pm_bus_of_match); Gr{oetje,eeting}s, Geert -- Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx 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
