linux-kernel - Re: [PATCH V7 6/9] vfio: platform: call

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Date:	Wed, 13 Jul 2016 14:11:38 -0600
From:	Alex Williamson <alex.williamson@...hat.com>
To:	Sinan Kaya <okaya@...eaurora.org>
Cc:	kvm@...r.kernel.org, timur@...eaurora.org, cov@...eaurora.org,
	jcm@...hat.com, eric.auger@...aro.org, linux-acpi@...r.kernel.org,
	agross@...eaurora.org, linux-arm-msm@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org,
	Baptiste Reynal <b.reynal@...tualopensystems.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH V7 6/9] vfio: platform: call _RST method when using ACPI

On Wed, 13 Jul 2016 15:39:25 -0400
Sinan Kaya <okaya@...eaurora.org> wrote:

> On 6/23/2016 2:59 PM, Alex Williamson wrote:
> > On Mon, 13 Jun 2016 00:26:38 -0400
> > Sinan Kaya <okaya@...eaurora.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@...eaurora.org>
> >> Reviewed-by: Eric Auger <eric.auger@...aro.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.   
> 
> I'll reorder to be consistent.
> 
> > 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.  
> 
> I like your idea. If you don't mind, I like capitals in macros. 

Sure.  Thanks,

Alex