Re: [PATCH V7 6/9] vfio: platform: call _RST method when using ACPI

[Alex Williamson <alex.williamson@redhat.com>]

On Thu, 23 Jun 2016 12:59:48 -0600
Alex Williamson <alex.williamson@redhat.com> wrote:

> On Mon, 13 Jun 2016 00:26:38 -0400
> Sinan Kaya <okaya@codeaurora.org> wrote:
> 
> > The device tree code checks for the presence of a reset driver and calls
> > the of_reset function pointer by looking up the reset driver as a module.
> > 
> > ACPI defines _RST method to perform device level reset. After the _RST
> > method is executed, the OS can resume using the device. _RST method is
> > expected to stop DMA transfers and IRQs.
> > 
> > This patch introduces two functions as vfio_platform_acpi_has_reset and
> > vfio_platform_acpi_call_reset. The has reset method is used to declare
> > reset capability via the ioctl flag VFIO_DEVICE_FLAGS_RESET. The call
> > reset function is used to execute the _RST ACPI method.
> > 
> > Signed-off-by: Sinan Kaya <okaya@codeaurora.org>
> > Reviewed-by: Eric Auger <eric.auger@linaro.org>
> > ---
> >  drivers/vfio/platform/vfio_platform_common.c | 51 ++++++++++++++++++++++++++++
> >  1 file changed, 51 insertions(+)
> > 
> > diff --git a/drivers/vfio/platform/vfio_platform_common.c b/drivers/vfio/platform/vfio_platform_common.c
> > index e7ce2c2..0ea8c26 100644
> > --- a/drivers/vfio/platform/vfio_platform_common.c
> > +++ b/drivers/vfio/platform/vfio_platform_common.c
> > @@ -73,21 +73,66 @@ static int vfio_platform_acpi_probe(struct vfio_platform_device *vdev,
> >  	}
> >  	return 0;
> >  }
> > +
> > +static int vfio_platform_acpi_call_reset(struct vfio_platform_device *vdev,
> > +					 const char **extra_dbg)
> > +{
> > +	struct device *dev = vdev->device;
> > +	acpi_handle handle = ACPI_HANDLE(dev);
> > +	acpi_status acpi_ret;
> > +	unsigned long long val;
> > +
> > +	acpi_ret = acpi_evaluate_integer(handle, "_RST", NULL, &val);
> > +	if (ACPI_FAILURE(acpi_ret)) {
> > +		if (extra_dbg)
> > +			*extra_dbg = acpi_format_exception(acpi_ret);
> > +		return -EINVAL;
> > +	}
> > +
> > +	return 0;
> > +}
> > +
> > +static bool vfio_platform_acpi_has_reset(struct vfio_platform_device *vdev)
> > +{
> > +	struct device *dev = vdev->device;
> > +	acpi_handle handle = ACPI_HANDLE(dev);
> > +
> > +	return acpi_has_method(handle, "_RST");
> > +}
> >  #else
> >  static inline int vfio_platform_acpi_probe(struct vfio_platform_device *vdev,
> >  					   struct device *dev)
> >  {
> >  	return -ENOENT;
> >  }
> > +
> > +static inline
> > +int vfio_platform_acpi_call_reset(struct vfio_platform_device *vdev,
> > +				  const char **extra_dbg)
> > +{
> > +	return -ENOENT;
> > +}
> > +
> > +static inline
> > +bool vfio_platform_acpi_has_reset(struct vfio_platform_device *vdev)
> > +{
> > +	return false;
> > +}
> >  #endif
> >  
> >  static bool vfio_platform_has_reset(struct vfio_platform_device *vdev)
> >  {
> > +	if (vdev->acpihid)
> > +		return vfio_platform_acpi_has_reset(vdev);
> > +
> >  	return vdev->of_reset ? true : false;
> >  }
> >  
> >  static void vfio_platform_get_reset(struct vfio_platform_device *vdev)
> >  {
> > +	if (vdev->acpihid)
> > +		return;
> > +
> >  	vdev->of_reset = vfio_platform_lookup_reset(vdev->compat,
> >  						    &vdev->reset_module);
> >  	if (!vdev->of_reset) {
> > @@ -99,6 +144,9 @@ static void vfio_platform_get_reset(struct vfio_platform_device *vdev)
> >  
> >  static void vfio_platform_put_reset(struct vfio_platform_device *vdev)
> >  {
> > +	if (vdev->acpihid)
> > +		return;
> > +
> >  	if (vdev->of_reset)
> >  		module_put(vdev->reset_module);
> >  }
> > @@ -177,6 +225,9 @@ static int vfio_platform_call_reset(struct vfio_platform_device *vdev,
> >  	if (vdev->of_reset) {
> >  		dev_info(vdev->device, "reset\n");
> >  		return vdev->of_reset(vdev);
> > +	} else if (vdev->acpihid) {
> > +		dev_info(vdev->device, "reset\n");
> > +		return vfio_platform_acpi_call_reset(vdev, extra_dbg);  
> 
> 
> nit, all the cases until this one prioritize ACPI over DT, here we have
> the opposite.  Granted we should never have of_reset set when acpihid
> is set.  A macro like
> 
> #define vfio_platform_is_acpi(vdev) (vdev->acpihid != NULL)
> 
> might be useful.

Oops, I accidentally picked the v7 version to reply to, but the nit
exists in v8 as well.  Thanks,

Alex