[PATCH] usb: dwc2: add shutdown callback to platform variant

[Doug Anderson]

Heiko,

On Fri, Dec 18, 2015 at 10:30 AM, Heiko Stübner
<heiko.stuebner at collabora.com> wrote:
> In specific conditions (involving usb hubs) dwc2 devices can create a
> lot of interrupts, even to the point of overwhelming devices running
> at low frequencies. Some devices need to do special clock handling
> at shutdown-time which may bring the system clock below the threshold
> of being able to handle the dwc2 interrupts. Disabling dwc2-irqs
> in a shutdown callbacks prevents reboots/poweroffs from getting stuck
> in such cases.
>
> The hsotg struct already contains an unused irq element, so we can
> just use it to store the irq number for the shutdown callback.
>
> Signed-off-by: Heiko Stuebner <heiko.stuebner at collabora.com>
> ---
> I'm also adapting the code on the clock-side to lessen the effects of
> the slow clock (see clk: rockchip: only enter pll slow-mode directly
> before reboots on rk3288), but this patch also fixes the issue of the
> overwhelming irq-number in itself and may be interesting for other/future
> platforms using the dwc2.
>
>
>  drivers/usb/dwc2/platform.c | 35 +++++++++++++++++++++++++++--------
>  1 file changed, 27 insertions(+), 8 deletions(-)
>
> diff --git a/drivers/usb/dwc2/platform.c b/drivers/usb/dwc2/platform.c
> index 39c1cbf..5510d07 100644
> --- a/drivers/usb/dwc2/platform.c
> +++ b/drivers/usb/dwc2/platform.c
> @@ -306,6 +306,25 @@ static int dwc2_driver_remove(struct platform_device *dev)
>         return 0;
>  }
>
> +/**
> + * dwc2_driver_shutdown() - Called on device shutdown
> + *
> + * @dev: Platform device
> + *
> + * In specific conditions (involving usb hubs) dwc2 devices can create a
> + * lot of interrupts, even to the point of overwhelming devices running
> + * at low frequencies. Some devices need to do special clock handling
> + * at shutdown-time which may bring the system clock below the threshold
> + * of being able to handle the dwc2 interrupts. Disabling dwc2-irqs
> + * prevents reboots/poweroffs from getting stuck in such cases.
> + */
> +static void dwc2_driver_shutdown(struct platform_device *dev)
> +{
> +       struct dwc2_hsotg *hsotg = platform_get_drvdata(dev);
> +
> +       disable_irq(hsotg->irq);

In one other place I see dwc2 getting the IRQ from the USB HCD
structure.  That is:

  dwc2_hsotg_to_hcd(hsotg)->irq

I wonder if that would be a good idea to do?  Then a future patch
could just remove the unused (and redundant) irq from the hsotg
structure?


Other than that this seems sane to me.

-Doug