[Intel-xe] [PATCH] drm/xe: Grab runtime PM over MMIO ioctl

[Matthew Auld]

On Wed, 14 Jun 2023 at 21:04, Matt Roper <matthew.d.roper at intel.com> wrote:
>
> The MMIO ioctl (which is generally used from IGT's xe_reg tool) may be
> called while the device is in D3, resulting in invalid results (i.e.,
> all registers read back as 0xFFFFFFFF, writes are dropped).  Make sure
> we grab runtime PM wakeref before performing register reads/writes.
>
> Signed-off-by: Matt Roper <matthew.d.roper at intel.com>

AFAIK we should use mem_access_get() for MMIO:
https://patchwork.freedesktop.org/patch/542124/?series=119213&rev=1

But that requires first fixing the races with mem_access which is
quite involved, so perhaps using runtime_get() directly here is fine
for now. We can just replace the instance here with mem_access once
that's ready.

Reviewed-by: Matthew Auld <matthew.auld at intel.com>

> ---
>  drivers/gpu/drm/xe/xe_mmio.c | 3 +++
>  1 file changed, 3 insertions(+)
>
> diff --git a/drivers/gpu/drm/xe/xe_mmio.c b/drivers/gpu/drm/xe/xe_mmio.c
> index f7a7f996b37f..5f4c8ae23771 100644
> --- a/drivers/gpu/drm/xe/xe_mmio.c
> +++ b/drivers/gpu/drm/xe/xe_mmio.c
> @@ -19,6 +19,7 @@
>  #include "xe_gt_mcr.h"
>  #include "xe_macros.h"
>  #include "xe_module.h"
> +#include "xe_pm.h"
>
>  #define XEHP_MTCFG_ADDR                XE_REG(0x101800)
>  #define TILE_COUNT             REG_GENMASK(15, 8)
> @@ -476,6 +477,7 @@ int xe_mmio_ioctl(struct drm_device *dev, void *data,
>          */
>         reg = XE_REG(args->addr);
>
> +       xe_pm_runtime_get(xe);
>         xe_force_wake_get(gt_to_fw(gt), XE_FORCEWAKE_ALL);
>
>         if (args->flags & DRM_XE_MMIO_WRITE) {
> @@ -519,6 +521,7 @@ int xe_mmio_ioctl(struct drm_device *dev, void *data,
>
>  exit:
>         xe_force_wake_put(gt_to_fw(gt), XE_FORCEWAKE_ALL);
> +       xe_pm_runtime_put(xe);
>
>         return ret;
>  }
> --
> 2.40.1
>