linux-kernel - Re: [PATCH V5 5/6] vfio: platform: call

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Date:	Mon, 23 May 2016 16:41:52 +0200
From:	Eric Auger <eric.auger@...aro.org>
To:	Sinan Kaya <okaya@...eaurora.org>, kvm@...r.kernel.org,
	timur@...eaurora.org, cov@...eaurora.org, jcm@...hat.com
Cc:	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>,
	Alex Williamson <alex.williamson@...hat.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH V5 5/6] vfio: platform: call _RST method when using ACPI

On 05/16/2016 04:13 AM, Sinan Kaya 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.
> 
> This patch checks the presence of _RST method and calls the _RST
> method when reset is requested.
> 
> Signed-off-by: Sinan Kaya <okaya@...eaurora.org>
> ---
>  drivers/vfio/platform/vfio_platform_common.c | 44 ++++++++++++++++++++++++++++
>  1 file changed, 44 insertions(+)
> 
> diff --git a/drivers/vfio/platform/vfio_platform_common.c b/drivers/vfio/platform/vfio_platform_common.c
> index d859d3b..095d5b7 100644
> --- a/drivers/vfio/platform/vfio_platform_common.c
> +++ b/drivers/vfio/platform/vfio_platform_common.c
> @@ -73,21 +73,59 @@ int vfio_platform_acpi_probe(struct vfio_platform_device *vdev,
>  	}
>  	return 0;
>  }
> +
> +static int vfio_platform_acpi_call_reset(struct vfio_platform_device *vdev)
> +{
> +	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))
> +		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
>  int vfio_platform_acpi_probe(struct vfio_platform_device *vdev,
>  			     struct device *dev)
>  {
>  	return -EINVAL;
>  }
> +
> +static int vfio_platform_acpi_call_reset(struct vfio_platform_device *vdev)
> +{
nit: inline
> +	return -EINVAL;
> +}
> +
> +static bool vfio_platform_acpi_has_reset(struct vfio_platform_device *vdev)
nit: inline

Besides Reviewed-by: Eric Auger <eric.auger@...aro.org>

It is not explictly written in the ACPI spec that _RST is expected to
stop DMA transfers and IRQs although this may be implicit in the notion
of "function level reset ". May be worth adding this info in the commit msg?

Best Regards

Eric
> +{
> +	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 +137,9 @@ 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 +218,9 @@ static int vfio_platform_call_reset(struct vfio_platform_device *vdev)
>  		dev_info(vdev->device, "reset\n");
>  		vdev->of_reset(vdev);
>  		return 0;
> +	} else if (vdev->acpihid) {
> +		dev_info(vdev->device, "reset\n");
> +		return vfio_platform_acpi_call_reset(vdev);
>  	}
>  
>  	dev_warn(vdev->device, "no reset function found!\n");
>