Date:   Thu, 11 Nov 2021 16:56:53 -0600
From:   Rob Herring <robh@...nel.org>
To:     Jim Quinlan <jim2101024@...il.com>
Cc:     PCI <linux-pci@...r.kernel.org>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Nicolas Saenz Julienne <nsaenz@...nel.org>,
        Mark Brown <broonie@...nel.org>,
        "maintainer:BROADCOM BCM7XXX ARM ARCHITECTURE" 
        <bcm-kernel-feedback-list@...adcom.com>,
        Jim Quinlan <james.quinlan@...adcom.com>,
        Sean V Kelley <sean.v.kelley@...el.com>,
        Jonathan Cameron <Jonathan.Cameron@...wei.com>,
        Qiuxu Zhuo <qiuxu.zhuo@...el.com>,
        Keith Busch <kbusch@...nel.org>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v8 5/8] PCI/portdrv: add mechanism to turn on subdev regulators

On Wed, Nov 10, 2021 at 4:15 PM Jim Quinlan <jim2101024@...il.com> wrote:
>
> Adds a mechanism inside the root port device to identify standard PCIe
> regulators in the DT, allocate them, and turn them on before the rest of
> the bus is scanned during pci_host_probe().  A root complex driver can
> leverage this mechanism by setting the pci_ops methods add_bus and
> remove_bus to pci_subdev_regulators_{add,remove}_bus.
>
> The allocated structure that contains the regulators is stored in
> dev.driver_data.
>
> The unabridged reason for doing this is as follows.  We would like the
> Broadcom STB PCIe root complex driver (and others) to be able to turn
> off/on regulators[1] that provide power to endpoint[2] devices.  Typically,
> the drivers of these endpoint devices are stock Linux drivers that are not
> aware that these regulator(s) exist and must be turned on for the driver to
> be probed.  The simple solution of course is to turn these regulators on at
> boot and keep them on.  However, this solution does not satisfy at least
> three of our usage modes:
>
> 1. For example, one customer uses multiple PCIe controllers, but wants the
> ability to, by script invoking and unbind, turn any or all of them by and
> their subdevices off to save power, e.g. when in battery mode.
>
> 2. Another example is when a watchdog script discovers that an endpoint
> device is in an unresponsive state and would like to unbind, power toggle,
> and re-bind just the PCIe endpoint and controller.
>
> 3. Of course we also want power turned off during suspend mode.  However,
> some endpoint devices may be able to "wake" during suspend and we need to
> recognise this case and veto the nominal act of turning off its regulator.
> Such is the case with Wake-on-LAN and Wake-on-WLAN support where PCIe
> end-point device needs to be kept powered on in order to receive network
> packets and wake-up the system.
>
> In all of these cases it is advantageous for the PCIe controller to govern
> the turning off/on the regulators needed by the endpoint device.  The first
> two cases can be done by simply unbinding and binding the PCIe controller,
> if the controller has control of these regulators.
>
> [1] These regulators typically govern the actual power supply to the
>     endpoint chip.  Sometimes they may be a the official PCIe socket
>     power -- such as 3.3v or aux-3.3v.  Sometimes they are truly
>     the regulator(s) that supply power to the EP chip.
>
> [2] The 99% configuration of our boards is a single endpoint device
>     attached to the PCIe controller.  I use the term endpoint but it could
>     possible mean a switch as well.
>
> Signed-off-by: Jim Quinlan <jim2101024@...il.com>
> ---
>  drivers/pci/bus.c              | 72 ++++++++++++++++++++++++++++++++++
>  drivers/pci/pci.h              |  8 ++++
>  drivers/pci/pcie/portdrv_pci.c | 32 +++++++++++++++
>  3 files changed, 112 insertions(+)
>
> diff --git a/drivers/pci/bus.c b/drivers/pci/bus.c
> index 3cef835b375f..c39fdf36b0ad 100644
> --- a/drivers/pci/bus.c
> +++ b/drivers/pci/bus.c
> @@ -419,3 +419,75 @@ void pci_bus_put(struct pci_bus *bus)
>         if (bus)
>                 put_device(&bus->dev);
>  }
> +
> +static void *alloc_subdev_regulators(struct device *dev)
> +{
> +       static const char * const supplies[] = {
> +               "vpcie3v3",
> +               "vpcie3v3aux",
> +               "vpcie12v",
> +       };
> +       const size_t size = sizeof(struct subdev_regulators)
> +               + sizeof(struct regulator_bulk_data) * ARRAY_SIZE(supplies);
> +       struct subdev_regulators *sr;
> +       int i;
> +
> +       sr = devm_kzalloc(dev, size, GFP_KERNEL);
> +
> +       if (sr) {
> +               sr->num_supplies = ARRAY_SIZE(supplies);
> +               for (i = 0; i < ARRAY_SIZE(supplies); i++)
> +                       sr->supplies[i].supply = supplies[i];
> +       }
> +
> +       return sr;
> +}
> +
> +
> +int pci_subdev_regulators_add_bus(struct pci_bus *bus)
> +{
> +       struct device *dev = &bus->dev;
> +       struct subdev_regulators *sr;
> +       int ret;
> +
> +       if (!pcie_is_port_dev(bus->self))
> +               return 0;
> +
> +       if (WARN_ON(bus->dev.driver_data))
> +               dev_err(dev, "multiple clients using dev.driver_data\n");
> +
> +       sr = alloc_subdev_regulators(&bus->dev);
> +       if (!sr)
> +               return -ENOMEM;
> +
> +       bus->dev.driver_data = sr;
> +       ret = regulator_bulk_get(dev, sr->num_supplies, sr->supplies);
> +       if (ret)
> +               return ret;
> +
> +       ret = regulator_bulk_enable(sr->num_supplies, sr->supplies);
> +       if (ret) {
> +               dev_err(dev, "failed to enable regulators for downstream device\n");
> +               return ret;
> +       }
> +
> +       return 0;
> +}
> +EXPORT_SYMBOL_GPL(pci_subdev_regulators_add_bus);

Can't these just go in the portdrv probe and remove functions now?

Rob

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