Re: [PATCH v10 09/10] drm/panfrost: Introduce huge tmpfs mountpoint option

[Boris Brezillon <boris.brezillon@collabora.com>]

On Fri, 28 Nov 2025 19:52:51 +0100
Loïc Molinari <loic.molinari@collabora.com> wrote:

> Introduce the 'panfrost.transparent_hugepage' boolean module parameter
> (false by default). When the parameter is set to true, a new tmpfs
> mountpoint is created and mounted using the 'huge=within_size'
> option. It's then used at GEM object creation instead of the default
> 'shm_mnt' mountpoint in order to enable Transparent Hugepage (THP) for
> the object (without having to rely on a system wide parameter).
> 
> v3:
> - use huge tmpfs mountpoint in drm_device
> 
> v4:
> - fix builds with CONFIG_TRANSPARENT_HUGEPAGE=n
> - clean up mountpoint creation error handling
> - print negative error value
> 
> v5:
> - use drm_gem_has_huge_tmp() helper
> - get rid of CONFIG_TRANSPARENT_HUGEPAGE ifdefs
> 
> v9:
> - replace drm_gem_has_huge_tmp() by drm_gem_get_huge_tmp()
> 
> Signed-off-by: Loïc Molinari <loic.molinari@collabora.com>
> Reviewed-by: Boris Brezillon <boris.brezillon@collabora.com>
> ---
>  drivers/gpu/drm/panfrost/panfrost_device.c |  3 +++
>  drivers/gpu/drm/panfrost/panfrost_drv.c    |  6 ++++++
>  drivers/gpu/drm/panfrost/panfrost_drv.h    |  9 +++++++++
>  drivers/gpu/drm/panfrost/panfrost_gem.c    | 18 ++++++++++++++++++
>  drivers/gpu/drm/panfrost/panfrost_gem.h    |  2 ++
>  5 files changed, 38 insertions(+)
>  create mode 100644 drivers/gpu/drm/panfrost/panfrost_drv.h
> 
> diff --git a/drivers/gpu/drm/panfrost/panfrost_device.c b/drivers/gpu/drm/panfrost/panfrost_device.c
> index c61b97af120c..dedc13e56631 100644
> --- a/drivers/gpu/drm/panfrost/panfrost_device.c
> +++ b/drivers/gpu/drm/panfrost/panfrost_device.c
> @@ -12,6 +12,7 @@
>  #include "panfrost_device.h"
>  #include "panfrost_devfreq.h"
>  #include "panfrost_features.h"
> +#include "panfrost_gem.h"
>  #include "panfrost_issues.h"
>  #include "panfrost_gpu.h"
>  #include "panfrost_job.h"
> @@ -267,6 +268,8 @@ int panfrost_device_init(struct panfrost_device *pfdev)
>  	if (err)
>  		goto out_job;
>  
> +	panfrost_gem_init(pfdev);
> +
>  	return 0;
>  out_job:
>  	panfrost_jm_fini(pfdev);
> diff --git a/drivers/gpu/drm/panfrost/panfrost_drv.c b/drivers/gpu/drm/panfrost/panfrost_drv.c
> index 7d8c7c337606..7f59568faa05 100644
> --- a/drivers/gpu/drm/panfrost/panfrost_drv.c
> +++ b/drivers/gpu/drm/panfrost/panfrost_drv.c
> @@ -858,6 +858,12 @@ static const struct drm_driver panfrost_drm_driver = {
>  #endif
>  };
>  
> +#ifdef CONFIG_TRANSPARENT_HUGEPAGE
> +bool panfrost_transparent_hugepage;

Same here, if there's no downside to enabling THP support, make it the
default.

> +module_param_named(transparent_hugepage, panfrost_transparent_hugepage, bool, 0400);
> +MODULE_PARM_DESC(transparent_hugepage, "Use a dedicated tmpfs mount point with Transparent Hugepage enabled (false = default)");
> +#endif
> +
>  static int panfrost_probe(struct platform_device *pdev)
>  {
>  	struct panfrost_device *pfdev;
> diff --git a/drivers/gpu/drm/panfrost/panfrost_drv.h b/drivers/gpu/drm/panfrost/panfrost_drv.h
> new file mode 100644
> index 000000000000..edeb093eb6da
> --- /dev/null
> +++ b/drivers/gpu/drm/panfrost/panfrost_drv.h
> @@ -0,0 +1,9 @@
> +// SPDX-License-Identifier: GPL-2.0 or MIT
> +/* Copyright 2025 Amazon.com, Inc. or its affiliates */
> +
> +#ifndef __PANFROST_DRV_H__
> +#define __PANFROST_DRV_H__
> +
> +extern bool panfrost_transparent_hugepage;
> +
> +#endif
> diff --git a/drivers/gpu/drm/panfrost/panfrost_gem.c b/drivers/gpu/drm/panfrost/panfrost_gem.c
> index 8041b65c6609..c1688a542ec2 100644
> --- a/drivers/gpu/drm/panfrost/panfrost_gem.c
> +++ b/drivers/gpu/drm/panfrost/panfrost_gem.c
> @@ -1,5 +1,6 @@
>  // SPDX-License-Identifier: GPL-2.0
>  /* Copyright 2019 Linaro, Ltd, Rob Herring <robh@kernel.org> */
> +/* Copyright 2025 Amazon.com, Inc. or its affiliates */
>  
>  #include <linux/cleanup.h>
>  #include <linux/err.h>
> @@ -10,9 +11,26 @@
>  #include <drm/panfrost_drm.h>
>  #include <drm/drm_print.h>
>  #include "panfrost_device.h"
> +#include "panfrost_drv.h"
>  #include "panfrost_gem.h"
>  #include "panfrost_mmu.h"
>  
> +void panfrost_gem_init(struct panfrost_device *pfdev)
> +{
> +	int err;
> +
> +	if (IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE) &&
> +	    !panfrost_transparent_hugepage)
> +		return;
> +
> +	err = drm_gem_huge_mnt_create(&pfdev->base, "within_size");
> +	if (drm_gem_get_huge_mnt(&pfdev->base))
> +		drm_info(&pfdev->base, "Using Transparent Hugepage\n");
> +	else if (err)
> +		drm_warn(&pfdev->base, "Can't use Transparent Hugepage (%d)\n",
> +			 err);
> +}
> +
>  #ifdef CONFIG_DEBUG_FS
>  static void panfrost_gem_debugfs_bo_add(struct panfrost_device *pfdev,
>  					struct panfrost_gem_object *bo)
> diff --git a/drivers/gpu/drm/panfrost/panfrost_gem.h b/drivers/gpu/drm/panfrost/panfrost_gem.h
> index 8de3e76f2717..1a62529ff06f 100644
> --- a/drivers/gpu/drm/panfrost/panfrost_gem.h
> +++ b/drivers/gpu/drm/panfrost/panfrost_gem.h
> @@ -124,6 +124,8 @@ drm_mm_node_to_panfrost_mapping(struct drm_mm_node *node)
>  	return container_of(node, struct panfrost_gem_mapping, mmnode);
>  }
>  
> +void panfrost_gem_init(struct panfrost_device *pfdev);
> +
>  struct drm_gem_object *panfrost_gem_create_object(struct drm_device *dev, size_t size);
>  
>  struct drm_gem_object *