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    SubjectRe: [PATCH 2/2] vfio: platform: Add generic DT reset support
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    Hi Geert,

    I have a suggestion to avoid having to use the IS_ERR_OR_NULL macro, see
    below:

    On Tue, 2018-02-13 at 17:36 +0100, 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,
    > 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;

    I'd avoid storing error values in vdev->reset_control at all, so this
    could be:

    if (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;

    if you assign to a local variable first here:

    struct reset_control *rstc;

    ...

    rstc = of_reset_control_get_exclusive(vdev->device->of_node, NULL);
    if (!IS_ERR(rstc)) {
    vdev->reset_control = rstc;
    return 0;
    }

    Also, please don't use __of_reset_control_get directly.

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

    return PTR_ERR(rstc);

    > }
    > 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);

    } else {
    if (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;
    >
    > /*

    regards
    Philipp

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