On Mon, Sep 6, 2021 at 12:54 AM Geert Uytterhoeven <geert@xxxxxxxxxxxxxx> wrote: > > 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. Not sure about mfd, but I want to make sure we don't confuse busses (which are typically added to a class) with these "simple bus" devices that are added to platform_bus. Also if these other buses are actually causing an issue, then then should implement their own stub driver or use try patch[2] if they are added to classes (devices on classes don't probe) [2] - https://lore.kernel.org/lkml/20210831224510.703253-1-saravanak@xxxxxxxxxx/ > > > [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. Right, and if they are platform devices that are equivalent to simple-bus (meaning, they don't do anything in Linux and just have their devices populated) we can add those to this list too. > > > + 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... But this doesn't affect simple-mfd though. > > > + } > > > > 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 ? Not needed? If CONFIG_ARM_AMBA isn't enabled, the device wouldn't be created in the first place. > > > + { .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? I wanted this table to be expandable as needed. That's why I'm intentionally not using of_default_bus_match_table[]. > > [*] Especially if "simple-pm-bus" and "simple-bus" would be treated > the same. They are not treated the same way. -Saravana > > > }; > > 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
