[PATCH v4 5/5] drivers: bus: Add Simple Power-Managed Bus Driver

[Ulf Hansson]

On 26 January 2015 at 17:16, Geert Uytterhoeven <geert+renesas at glider.be> wrote:
> Add a driver for transparent busses that don't need a real driver, but
> where the bus controller is part of a PM domain, or under the control of
> a functional clock.  Typically, the bus controller's PM domain and/or
> clock must be enabled for child devices connected to the bus (either
> on-SoC or externally) to function.
>
> Hence the sole purpose of this driver is to enable its clock and PM
> domain (if exist(s)), which are specified in the DT and managed from
> platform and PM domain code, and to probe for child devices.
>
> Due to the child-parent relationship with devices connected to the bus,
> PM domain and clock state transitions are handled in the correct order.
>
> Signed-off-by: Geert Uytterhoeven <geert+renesas at glider.be>
> Tested-by: Ulrich Hecht <ulrich.hecht+renesas at gmail.com>
> ---
> v4:
>   - Bind against the generic "simple-pm-bus" instead of "renesas,bsc",
>   - Explicitly call of_platform_populate() after pm_runtime_enable() to
>     enforce ordering, instead of depending on claimed compatibility with
>     "simple-bus",
>
> v3:
>   - Add Tested-by,
>
> v2:
>   - Rename from "Renesas Bus State Controller Driver" (renesas-bsc) to
>     "Simple Power-Managed Bus Driver" (simple-pm-bus),
>   - Change module license to GPL v2,
>   - Change email address to geert+renesas at glider.be.
> ---
>  drivers/bus/Kconfig         | 13 ++++++++++
>  drivers/bus/Makefile        |  1 +
>  drivers/bus/simple-pm-bus.c | 58 +++++++++++++++++++++++++++++++++++++++++++++
>  3 files changed, 72 insertions(+)
>  create mode 100644 drivers/bus/simple-pm-bus.c
>
> diff --git a/drivers/bus/Kconfig b/drivers/bus/Kconfig
> index 626960819e6df16c..7e9c2674af81d6e9 100644
> --- a/drivers/bus/Kconfig
> +++ b/drivers/bus/Kconfig
> @@ -58,6 +58,19 @@ config OMAP_OCP2SCP
>           OCP2SCP and in OMAP5, both USB PHY and SATA PHY is connected via
>           OCP2SCP.
>
> +config SIMPLE_PM_BUS
> +       bool "Simple Power-Managed Bus Driver"
> +       depends on OF && PM
> +       depends on ARCH_SHMOBILE || COMPILE_TEST
> +       help
> +         Driver for transparent busses that don't need a real driver, but
> +         where the bus controller is part of a PM domain, or under the control
> +         of a functional clock, and thus relies on runtime PM for managing
> +         this PM domain and/or clock.
> +         An example of such a bus controller is the Renesas Bus State
> +         Controller (BSC, sometimes called "LBSC within Bus Bridge", or
> +         "External Bus Interface") as found on several Renesas ARM SoCs.
> +
>  config VEXPRESS_CONFIG
>         bool "Versatile Express configuration bus"
>         default y if ARCH_VEXPRESS
> diff --git a/drivers/bus/Makefile b/drivers/bus/Makefile
> index 3cfaf2c7f25ac4f0..e023a2bec664d900 100644
> --- a/drivers/bus/Makefile
> +++ b/drivers/bus/Makefile
> @@ -14,4 +14,5 @@ obj-$(CONFIG_MVEBU_MBUS)      += mvebu-mbus.o
>  obj-$(CONFIG_OMAP_INTERCONNECT)        += omap_l3_smx.o omap_l3_noc.o
>
>  obj-$(CONFIG_OMAP_OCP2SCP)     += omap-ocp2scp.o
> +obj-$(CONFIG_SIMPLE_PM_BUS)    += simple-pm-bus.o
>  obj-$(CONFIG_VEXPRESS_CONFIG)  += vexpress-config.o
> diff --git a/drivers/bus/simple-pm-bus.c b/drivers/bus/simple-pm-bus.c
> new file mode 100644
> index 0000000000000000..c5eb46cbf388b507
> --- /dev/null
> +++ b/drivers/bus/simple-pm-bus.c
> @@ -0,0 +1,58 @@
> +/*
> + * Simple Power-Managed Bus Driver
> + *
> + * Copyright (C) 2014-2015 Glider bvba
> + *
> + * This file is subject to the terms and conditions of the GNU General Public
> + * License.  See the file "COPYING" in the main directory of this archive
> + * for more details.
> + */
> +
> +#include <linux/module.h>
> +#include <linux/of_platform.h>
> +#include <linux/platform_device.h>
> +#include <linux/pm_runtime.h>
> +
> +
> +static int simple_pm_bus_probe(struct platform_device *pdev)
> +{
> +       struct device_node *np = pdev->dev.of_node;
> +
> +       dev_dbg(&pdev->dev, "%s\n", __func__);
> +
> +       pm_runtime_enable(&pdev->dev);
> +
> +       if (np)
> +               of_platform_populate(np, NULL, NULL, &pdev->dev);
> +

I am not sure my comments is valid in this initial step. Yet, you
state in the DT documentation, that this driver supports clocks and PM
domains.

How you are going add that support it quite interesting. :-) I also
especially interested how the interaction (child to parents) through
runtime PM will look like.

Overall, I like the idea in patchset, but I would like to understand a
bit more around the above.

Kind regards
Uffe

> +       return 0;
> +}
> +
> +static int simple_pm_bus_remove(struct platform_device *pdev)
> +{
> +       dev_dbg(&pdev->dev, "%s\n", __func__);
> +
> +       pm_runtime_disable(&pdev->dev);
> +       return 0;
> +}
> +
> +static const struct of_device_id simple_pm_bus_of_match[] = {
> +       { .compatible = "simple-pm-bus", },
> +       { /* sentinel */ }
> +};
> +MODULE_DEVICE_TABLE(of, simple_pm_bus_of_match);
> +
> +static struct platform_driver simple_pm_bus_driver = {
> +       .probe = simple_pm_bus_probe,
> +       .remove = simple_pm_bus_remove,
> +       .driver = {
> +               .name = "simple-pm-bus",
> +               .of_match_table = simple_pm_bus_of_match,
> +       },
> +};
> +
> +module_platform_driver(simple_pm_bus_driver);
> +
> +MODULE_DESCRIPTION("Simple Power-Managed Bus Driver");
> +MODULE_AUTHOR("Geert Uytterhoeven <geert+renesas at glider.be>");
> +MODULE_LICENSE("GPL v2");
> --
> 1.9.1
>