On Tue, Apr 10, 2018 at 05:53:47PM +0200, Geert Uytterhoeven wrote:
> Vfio-platform requires reset support, provided either by ACPI, or, on DT
> platforms, by a device-specific reset driver matching against the
> device's compatible value.
> 
> On many SoCs, devices are connected to an SoC-internal reset controller.
> If the reset hierarchy is described in DT using "resets" properties,
> such devices can be reset in a generic way through the reset controller
> subsystem.  Hence add support for this, avoiding the need to write
> device-specific reset drivers for each single device on affected SoCs.
> 
> Devices that do require a more complex reset procedure can still provide
> a device-specific reset driver, as that takes precedence.
> 
> Note that this functionality depends on CONFIG_RESET_CONTROLLER=y, and
> becomes a no-op (as in: "No reset function found for device") if reset
> controller support is disabled.
> 
> Signed-off-by: Geert Uytterhoeven <geert+rene...@glider.be>
> ---
> v2:
>   - Don't store error values in vdev->reset_control,
>   - Use of_reset_control_get_exclusive() instead of
>     __of_reset_control_get(),
>   - Improve description.
> ---
>  drivers/vfio/platform/vfio_platform_common.c  | 26 ++++++++++++++++++++++++--
>  drivers/vfio/platform/vfio_platform_private.h |  1 +
>  2 files changed, 25 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/vfio/platform/vfio_platform_common.c 
> b/drivers/vfio/platform/vfio_platform_common.c
> index b60bb5326668498c..3c13327b2777f8ec 100644
> --- a/drivers/vfio/platform/vfio_platform_common.c
> +++ b/drivers/vfio/platform/vfio_platform_common.c
> @@ -17,6 +17,7 @@
>  #include <linux/iommu.h>
>  #include <linux/module.h>
>  #include <linux/mutex.h>
> +#include <linux/reset.h>
>  #include <linux/slab.h>
>  #include <linux/types.h>
>  #include <linux/uaccess.h>
> @@ -112,11 +113,19 @@ static bool vfio_platform_has_reset(struct 
> vfio_platform_device *vdev)
>       if (VFIO_PLATFORM_IS_ACPI(vdev))
>               return vfio_platform_acpi_has_reset(vdev);
>  
> -     return vdev->of_reset ? true : false;
> +     if (vdev->of_reset)
> +             return true;
> +
> +     if (vdev->reset_control)
> +             return true;
> +
> +     return false;

I wonder if the above would be better expressed as:

        return vdev->of_reset || vdev->reset_control;

>  }
>  
>  static int vfio_platform_get_reset(struct vfio_platform_device *vdev)
>  {
> +     struct reset_control *rstc;
> +
>       if (VFIO_PLATFORM_IS_ACPI(vdev))
>               return vfio_platform_acpi_has_reset(vdev) ? 0 : -ENOENT;
>  
> @@ -127,8 +136,16 @@ static int vfio_platform_get_reset(struct 
> vfio_platform_device *vdev)
>               vdev->of_reset = vfio_platform_lookup_reset(vdev->compat,
>                                                       &vdev->reset_module);
>       }
> +     if (vdev->of_reset)
> +             return 0;
> +
> +     rstc = of_reset_control_get_exclusive(vdev->device->of_node, NULL);
> +     if (!IS_ERR(rstc)) {
> +             vdev->reset_control = rstc;
> +             return 0;
> +     }
>  
> -     return vdev->of_reset ? 0 : -ENOENT;
> +     return PTR_ERR(rstc);
>  }
>  
>  static void vfio_platform_put_reset(struct vfio_platform_device *vdev)
> @@ -138,6 +155,8 @@ static void vfio_platform_put_reset(struct 
> vfio_platform_device *vdev)
>  
>       if (vdev->of_reset)
>               module_put(vdev->reset_module);
> +
> +     reset_control_put(vdev->reset_control);
>  }
>  
>  static int vfio_platform_regions_init(struct vfio_platform_device *vdev)
> @@ -217,6 +236,9 @@ static int vfio_platform_call_reset(struct 
> vfio_platform_device *vdev,
>       } else if (vdev->of_reset) {
>               dev_info(vdev->device, "reset\n");
>               return vdev->of_reset(vdev);
> +     } else if (vdev->reset_control) {
> +             dev_info(vdev->device, "reset\n");

Would it be useful to differentiate between the above two informational
messages?

> +             return reset_control_reset(vdev->reset_control);
>       }
>  
>       dev_warn(vdev->device, "no reset function found!\n");
> diff --git a/drivers/vfio/platform/vfio_platform_private.h 
> b/drivers/vfio/platform/vfio_platform_private.h
> index 85ffe5d9d1abd94e..a56e80ae5986540b 100644
> --- a/drivers/vfio/platform/vfio_platform_private.h
> +++ b/drivers/vfio/platform/vfio_platform_private.h
> @@ -60,6 +60,7 @@ struct vfio_platform_device {
>       const char                      *compat;
>       const char                      *acpihid;
>       struct module                   *reset_module;
> +     struct reset_control            *reset_control;
>       struct device                   *device;
>  
>       /*
> -- 
> 2.7.4
> 

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