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SubjectRe: [PATCH/RFC v4 2/2] vfio: platform: Add generic reset controller support
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Hi Geert,

On 9/17/18 6:39 PM, Geert Uytterhoeven wrote:
> Vfio-platform requires dedicated 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.
> If the reset hierarchy is described in DT using "resets" properties, or
> in lookup tables in platform code, such devices can be reset in a
> generic way through the reset controller subsystem. Hence add support
> for this, avoiding the need to write device-specific reset drivers for
> each single device on affected SoCs.
>
> Devices that do 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 (as in: "No reset function found for device") if reset
> controller support is disabled.
>
> Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
> Reviewed-by: Philipp Zabel <p.zabel@pengutronix.de>
> Reviewed-by: Simon Horman <horms+renesas@verge.net.au>
> ---
> v4:
> - Add Reviewed-by,
> - Use new RFC reset_control_get_dedicated() instead of
> of_reset_control_get_exclusive(), to (a) make it more generic, and
> (b) make sure the reset returned is really a dedicated reset, and
> does not affect other devices,
>
> v3:
> - Add Reviewed-by,
> - Merge similar checks in vfio_platform_has_reset(),
>
> v2:
> - Don't store error values in vdev->reset_control,
> - Use of_reset_control_get_exclusive() instead of
> __of_reset_control_get(),
> - Improve description.
>
> ---
> drivers/vfio/platform/vfio_platform_common.c | 20 +++++++++++++++++--
> drivers/vfio/platform/vfio_platform_private.h | 1 +
> 2 files changed, 19 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/vfio/platform/vfio_platform_common.c b/drivers/vfio/platform/vfio_platform_common.c
> index c0cd824be2b767be..eb77fe87f3663e3e 100644
> --- a/drivers/vfio/platform/vfio_platform_common.c
> +++ b/drivers/vfio/platform/vfio_platform_common.c
> @@ -18,6 +18,7 @@
> #include <linux/module.h>
> #include <linux/mutex.h>
> #include <linux/pm_runtime.h>
> +#include <linux/reset.h>
> #include <linux/slab.h>
> #include <linux/types.h>
> #include <linux/uaccess.h>
> @@ -113,11 +114,13 @@ 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;
> + return vdev->of_reset || vdev->reset_control;
> }
>
> static int vfio_platform_get_reset(struct vfio_platform_device *vdev)
> {
> + struct reset_control *rstc;
> +
> if (VFIO_PLATFORM_IS_ACPI(vdev))
> return vfio_platform_acpi_has_reset(vdev) ? 0 : -ENOENT;
>
> @@ -128,8 +131,16 @@ 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;
> +
> + rstc = reset_control_get_dedicated(vdev->device, NULL);
> + if (!IS_ERR(rstc)) {
> + vdev->reset_control = rstc;
> + return 0;
> + }
>
> - return vdev->of_reset ? 0 : -ENOENT;
> + return PTR_ERR(rstc);
This changes the returned value as seen by the user (probe returned
valud). Can we keep -ENOENT in case of no reset controller found?

Otherwise looks good to me with the new "dedicated" reset semantics.

Thanks

Eric
> }
>
> static void vfio_platform_put_reset(struct vfio_platform_device *vdev)
> @@ -139,6 +150,8 @@ 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)
> @@ -218,6 +231,9 @@ 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 (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;
>
> /*
>

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