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

Ulf Hansson
2021-09-09T11:02:26Z

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>

Tested-by: Ulf Hansson <ulf.hansson@linaro.org>

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
>