[v2,00/11] drm: Improve fbdev emulation for DMA-able framebuffers

Add fbdev helpers for framebuffers in DMA-able memory and update
fbdev emulation in the respective DRM drivers. DMA memory used to
handled as system memory. Improve this and prepare for possible
future changes.

Patch 1 adds initializer macros for struct fb_ops and a Kconfig
token for framebuffers in DMA memory.

Patches 2 to 4 update fbdev-dma and tegra. No functional changes
are expected as both used system memory before.

Patches 5 and 6 update exynos to use DMA helpers. Exynos incorrectly
used fbdev's I/O-memory helpers. Fix this.

Patches 7 to 9 update omapdrm to use DMA helpers. Patch 7 first
reworks the driver's mmap to current best practices. This also makes
it suitable for use with fbdev, which patches 8 and 9 implement.

Patchies 10 removes some fbdev macros for system memory that are now
unused; patch 11 fixes some comments.

The patchset would ideally go through drm-misc-next. Future patches
can build upon it and update fbdev drivers in similar ways.

v2:
	* fix omap mmap flags
	* drop FBINFO_DEFAULT from patches
	* minor cleanups

Thomas Zimmermann (11):
  fbdev: Add fb_ops init macros for framebuffers in DMA-able memory
  drm/fbdev-dma: Use fbdev DMA helpers
  drm/tegra: Use fbdev DMA helpers
  drm/tegra: Set fbdev FBINFO_VIRTFB flag
  drm/exynos: Use fbdev DMA helpers
  drm/exynos: Set fbdev FBINFO_VIRTFB flag
  drm/omapdrm: Set VM flags in GEM-object mmap function
  drm/omapdrm: Use GEM mmap for fbdev emulation
  drm/omapdrm: Set fbdev FBINFO_VIRTFB flag
  fbdev: Remove FB_DEFAULT_SYS_OPS
  fbdev: Harmonize some comments in <linux/fb.h>

 drivers/gpu/drm/Kconfig                   |  2 +-
 drivers/gpu/drm/drm_fbdev_dma.c           |  4 ++--
 drivers/gpu/drm/exynos/Kconfig            |  2 +-
 drivers/gpu/drm/exynos/exynos_drm_fbdev.c |  5 ++--
 drivers/gpu/drm/omapdrm/Kconfig           |  2 +-
 drivers/gpu/drm/omapdrm/omap_drv.c        | 12 +---------
 drivers/gpu/drm/omapdrm/omap_fbdev.c      | 16 +++++++++++--
 drivers/gpu/drm/omapdrm/omap_gem.c        | 24 +++++--------------
 drivers/gpu/drm/omapdrm/omap_gem.h        |  3 ---
 drivers/gpu/drm/omapdrm/omap_gem_dmabuf.c |  7 +-----
 drivers/gpu/drm/tegra/Kconfig             |  2 +-
 drivers/gpu/drm/tegra/fbdev.c             |  5 ++--
 drivers/video/fbdev/Kconfig               |  8 +++++++
 include/linux/fb.h                        | 29 ++++++++++-------------
 14 files changed, 55 insertions(+), 66 deletions(-)

On Thu, Jul 06, 2023 at 02:46:42PM +0200, Thomas Zimmermann wrote:
> Mark the framebuffer with FBINFO_VIRTFB. The framebuffer range is
> in DMA-able memory and should be accessed with the CPU's regular
> memory ops.
> 
> v2:
> 	* drop FBINFO_DEFAULT
> 
> Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
> Reviewed-by: Javier Martinez Canillas <javierm@redhat.com>
> Acked-by: Maxime Ripard <mripard@kernel.org>
> Cc: Thierry Reding <thierry.reding@gmail.com>
> Cc: Mikko Perttunen <mperttunen@nvidia.com>
> ---
>  drivers/gpu/drm/tegra/fbdev.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/drivers/gpu/drm/tegra/fbdev.c b/drivers/gpu/drm/tegra/fbdev.c
> index 82577b7c88da..d8460c5dc91e 100644
> --- a/drivers/gpu/drm/tegra/fbdev.c
> +++ b/drivers/gpu/drm/tegra/fbdev.c
> @@ -132,6 +132,7 @@ static int tegra_fbdev_probe(struct drm_fb_helper *helper,
>  		}
>  	}
>  
> +	info->flags |= FBINFO_VIRTFB;
>  	info->screen_base = (void __iomem *)bo->vaddr + offset;

As part of this, do we also need to set info->screen_buffer instead of
info->screen_base? The drm_fbdev_dma_helper functions do that.

Thierry

>  	info->screen_size = size;
>  	info->fix.smem_start = (unsigned long)(bo->iova + offset);
> -- 
> 2.41.0
>

Hi,

> -----Original Message-----
> From: Thomas Zimmermann <tzimmermann@suse.de>
> Sent: Thursday, July 6, 2023 9:47 PM
> To: javierm@redhat.com; maarten.lankhorst@linux.intel.com;
> mripard@kernel.org
> Cc: dri-devel@lists.freedesktop.org; linux-arm-kernel@lists.infradead.org;
> linux-samsung-soc@vger.kernel.org; linux-tegra@vger.kernel.org; linux-
> fbdev@vger.kernel.org; Thomas Zimmermann <tzimmermann@suse.de>; Inki Dae
> <inki.dae@samsung.com>; Seung-Woo Kim <sw0312.kim@samsung.com>; Kyungmin
> Park <kyungmin.park@samsung.com>; Krzysztof Kozlowski
> <krzysztof.kozlowski@linaro.org>; Alim Akhtar <alim.akhtar@samsung.com>
> Subject: [PATCH v2 06/11] drm/exynos: Set fbdev FBINFO_VIRTFB flag
> 
> Mark the framebuffer with FBINFO_VIRTFB. The framebuffer range is
> in DMA-able memory and should be accessed with the CPU's regular
> memory ops.
> 
> v2:
> 	* drop FBINFO_FLAG_DEFAULT
> 
> Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
> Reviewed-by: Javier Martinez Canillas <javierm@redhat.com>
> Acked-by: Maxime Ripard <mripard@kernel.org>

Acked-by : Inki Dae <inki.dae@samsung.com>

Thanks,
Inki Dae

> Cc: Inki Dae <inki.dae@samsung.com>
> Cc: Seung-Woo Kim <sw0312.kim@samsung.com>
> Cc: Kyungmin Park <kyungmin.park@samsung.com>
> Cc: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
> Cc: Alim Akhtar <alim.akhtar@samsung.com>
> ---
>  drivers/gpu/drm/exynos/exynos_drm_fbdev.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/drivers/gpu/drm/exynos/exynos_drm_fbdev.c
> b/drivers/gpu/drm/exynos/exynos_drm_fbdev.c
> index 7ca3424b59ce..828318de8529 100644
> --- a/drivers/gpu/drm/exynos/exynos_drm_fbdev.c
> +++ b/drivers/gpu/drm/exynos/exynos_drm_fbdev.c
> @@ -79,6 +79,7 @@ static int exynos_drm_fbdev_update(struct drm_fb_helper
> *helper,
>  	offset = fbi->var.xoffset * fb->format->cpp[0];
>  	offset += fbi->var.yoffset * fb->pitches[0];
> 
> +	fbi->flags |= FBINFO_VIRTFB;
>  	fbi->screen_buffer = exynos_gem->kvaddr + offset;
>  	fbi->screen_size = size;
>  	fbi->fix.smem_len = size;
> --
> 2.41.0