[PATCH RFC 3/3] drm/i915/display: Implement fb_mmap callback function

[Ville Syrjälä]

On Mon, Mar 06, 2023 at 11:28:50AM +0100, Nirmoy Das wrote:
> If stolen memory allocation fails for fbdev, the driver will
> fallback to system memory. Calculation of smem_start is wrong
> for such framebuffer objs if the platform comes with no gmadr or
> no aperture. Solve this by adding fb_mmap callback which also gives
> driver more control.
> 
> Signed-off-by: Nirmoy Das <nirmoy.das at intel.com>
> ---
>  drivers/gpu/drm/i915/display/intel_fbdev.c | 20 ++++++++++++++++++++
>  1 file changed, 20 insertions(+)
> 
> diff --git a/drivers/gpu/drm/i915/display/intel_fbdev.c b/drivers/gpu/drm/i915/display/intel_fbdev.c
> index 98ae3a3a986a..ed0f9e2af3ed 100644
> --- a/drivers/gpu/drm/i915/display/intel_fbdev.c
> +++ b/drivers/gpu/drm/i915/display/intel_fbdev.c
> @@ -40,8 +40,10 @@
>  #include <drm/drm_crtc.h>
>  #include <drm/drm_fb_helper.h>
>  #include <drm/drm_fourcc.h>
> +#include <drm/drm_gem_framebuffer_helper.h>
>  
>  #include "gem/i915_gem_lmem.h"
> +#include "gem/i915_gem_mman.h"
>  
>  #include "i915_drv.h"
>  #include "intel_display_types.h"
> @@ -120,6 +122,23 @@ static int intel_fbdev_pan_display(struct fb_var_screeninfo *var,
>  	return ret;
>  }
>  
> +#define to_intel_fbdev(x) container_of(x, struct intel_fbdev, helper)
> +static int intel_fbdev_mmap(struct fb_info *info, struct vm_area_struct *vma)
> +{
> +	struct intel_fbdev *fbdev = to_intel_fbdev(info->par);
> +	struct drm_gem_object *bo = drm_gem_fb_get_obj(&fbdev->fb->base, 0);
> +	struct drm_i915_gem_object *obj = to_intel_bo(bo);
> +	struct drm_device *dev = fbdev->helper.dev;

You seem to be missing the fb vs. mmio handling here entirely.

> +
> +	vma->vm_page_prot =
> +			pgprot_writecombine(vm_get_page_prot(vma->vm_flags));

Does that do something sane on eg. !PAT?

> +
> +	if (obj->stolen)
> +		return vm_iomap_memory(vma, info->fix.smem_start,
> +				       info->fix.smem_len);

Why doesn't i915_gem_object_mmap() know how to handle stolen?

> +
> +	return i915_gem_object_mmap(obj, vma);
> +}
>  static const struct fb_ops intelfb_ops = {
>  	.owner = THIS_MODULE,
>  	DRM_FB_HELPER_DEFAULT_OPS,
> @@ -131,6 +150,7 @@ static const struct fb_ops intelfb_ops = {
>  	.fb_imageblit = drm_fb_helper_cfb_imageblit,
>  	.fb_pan_display = intel_fbdev_pan_display,
>  	.fb_blank = intel_fbdev_blank,
> +	.fb_mmap = intel_fbdev_mmap,
>  };
>  
>  static int intelfb_alloc(struct drm_fb_helper *helper,
> -- 
> 2.39.0

-- 
Ville Syrjälä
Intel