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Subject[PATCH 2/2] vfio: platform: Add generic DT reset support
Date
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,
and can be reset in a generic way. Hence add support to reset such
devices using the reset controller subsystem, provided the reset
hierarchy is described correctly in DT using the "resets" property.

Devices that 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 if reset controller support is disabled.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
---
drivers/vfio/platform/vfio_platform_common.c | 23 +++++++++++++++++++++--
drivers/vfio/platform/vfio_platform_private.h | 1 +
2 files changed, 22 insertions(+), 2 deletions(-)

diff --git a/drivers/vfio/platform/vfio_platform_common.c b/drivers/vfio/platform/vfio_platform_common.c
index b60bb5326668498c..5d1e48f96e423508 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>
@@ -112,7 +113,13 @@ 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 (!IS_ERR_OR_NULL(vdev->reset_control))
+ return true;
+
+ return false;
}

static int vfio_platform_get_reset(struct vfio_platform_device *vdev)
@@ -127,8 +134,15 @@ 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;
+
+ vdev->reset_control = __of_reset_control_get(vdev->device->of_node,
+ NULL, 0, false, false);
+ if (!IS_ERR(vdev->reset_control))
+ return 0;

- return vdev->of_reset ? 0 : -ENOENT;
+ return PTR_ERR(vdev->reset_control);
}

static void vfio_platform_put_reset(struct vfio_platform_device *vdev)
@@ -138,6 +152,8 @@ 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 +233,9 @@ 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 (!IS_ERR_OR_NULL(vdev->reset_control)) {
+ dev_info(vdev->device, "reset\n");
+ 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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