On Sat, Feb 01, 2020 at 01:27:41PM +0100, Thomas Zimmermann wrote:
> Devices with low amount of dedicated video memory may not be able
> to use all possible display modes, as the framebuffers may not fit
> into VRAM. The new helper function drm_vram_helper_mode_valid()
> implements a simple test to sort out all display modes that can
> not be used in any case. Drivers should call this function from
> struct drm_mode_config_funcs.mode_valid.
>
> Calling drm_vram_helper_mode_valid() works best for 32-bit framebuffers;
> drivers with framebuffers of different color depth can use
> drm_vram_helper_mode_valid_internal() instead.
>
> The functionality was originally implemented by the ast driver, which
> is being converted as well.
>
> Signed-off-by: Thomas Zimmermann <tzimmermann@xxxxxxx>
> ---
> drivers/gpu/drm/ast/ast_main.c | 24 +--------
> drivers/gpu/drm/drm_gem_vram_helper.c | 76 +++++++++++++++++++++++++++
> include/drm/drm_gem_vram_helper.h | 14 +++++
> 3 files changed, 91 insertions(+), 23 deletions(-)
>
> diff --git a/drivers/gpu/drm/ast/ast_main.c b/drivers/gpu/drm/ast/ast_main.c
> index b79f484e9bd2..18a0a4ce00f6 100644
> --- a/drivers/gpu/drm/ast/ast_main.c
> +++ b/drivers/gpu/drm/ast/ast_main.c
> @@ -388,31 +388,9 @@ static int ast_get_dram_info(struct drm_device *dev)
> return 0;
> }
>
> -enum drm_mode_status ast_mode_config_mode_valid(struct drm_device *dev,
> - const struct drm_display_mode *mode)
> -{
> - static const unsigned long max_bpp = 4; /* DRM_FORMAT_XRGBA8888 */
> -
> - struct ast_private *ast = dev->dev_private;
> - unsigned long fbsize, fbpages, max_fbpages;
> -
> - /* To support double buffering, a framebuffer may not
> - * consume more than half of the available VRAM.
> - */
> - max_fbpages = (ast->vram_size / 2) >> PAGE_SHIFT;
> -
> - fbsize = mode->hdisplay * mode->vdisplay * max_bpp;
> - fbpages = DIV_ROUND_UP(fbsize, PAGE_SIZE);
> -
> - if (fbpages > max_fbpages)
> - return MODE_MEM;
> -
> - return MODE_OK;
> -}
> -
> static const struct drm_mode_config_funcs ast_mode_funcs = {
> .fb_create = drm_gem_fb_create,
> - .mode_valid = ast_mode_config_mode_valid,
> + .mode_valid = drm_vram_helper_mode_valid,
> .atomic_check = drm_atomic_helper_check,
> .atomic_commit = drm_atomic_helper_commit,
> };
> diff --git a/drivers/gpu/drm/drm_gem_vram_helper.c b/drivers/gpu/drm/drm_gem_vram_helper.c
> index a4863326061a..89aebd500655 100644
> --- a/drivers/gpu/drm/drm_gem_vram_helper.c
> +++ b/drivers/gpu/drm/drm_gem_vram_helper.c
> @@ -1141,3 +1141,79 @@ void drm_vram_helper_release_mm(struct drm_device *dev)
> dev->vram_mm = NULL;
> }
> EXPORT_SYMBOL(drm_vram_helper_release_mm);
> +
> +/*
> + * Mode-config helpers
> + */
> +
> +/**
> + * drm_vram_helper_mode_valid_internal - Tests if a display mode's
> + * framebuffer fits into the available video memory.
> + * @dev: the DRM device
> + * @mode: the mode to test
> + * @max_bpp: the maximum number of bytes per pixel
Does this render correctly? I thought an empty comment line is required
between comments and the free-form paragraphs ... Also usual style (in drm
at least) is that the Returns: block is more towards the end of the text,
and not indented.
> + * Returns:
> + * MODE_OK the display mode is supported, or an error code of type
> + * enum drm_mode_status otherwise.
> + *
> + * This function tests if enough video memory is available using the
> + * specified display mode. Atomic modesetting requires importing the
> + * designated framebuffer into video memory before evicting the active
> + * one. Hence, any framebuffer may consume at most half of the available
> + * VRAM. Display modes that require a larger framebuffer can not be used,
> + * even of the CRTC does support them.
> + *
> + * Drivers should call this function from
> + * struct drm_mode_config_funcs.mode_valid. See drm_vram_helper_mode_valid()
> + * for framebuffers that use at most 32-bit color depth.
> + *
> + * Note:
> + * The function can only test if the display mode is supported in
> + * general. If you have too many framebuffers pinned to video memory,
> + * a display mode may still not be usable in practice.
> + */
> +enum drm_mode_status
> +drm_vram_helper_mode_valid_internal(struct drm_device *dev,
> + const struct drm_display_mode *mode,
> + unsigned long max_bpp)
> +{
> + struct drm_vram_mm *vmm = dev->vram_mm;
> + unsigned long fbsize, fbpages, max_fbpages;
> +
> + if (!dev->vram_mm)
This is a driver bug imo (most likely of enabling hotplug/output detection
before the vram handling is set up), needs to be wrapped in a WARN_ON to
catch this.
> + return MODE_BAD;
> +
> + max_fbpages = (vmm->vram_size / 2) >> PAGE_SHIFT;
> +
> + fbsize = mode->hdisplay * mode->vdisplay * max_bpp;
> + fbpages = DIV_ROUND_UP(fbsize, PAGE_SIZE);
> +
> + if (fbpages > max_fbpages)
> + return MODE_MEM;
> +
> + return MODE_OK;
> +}
> +EXPORT_SYMBOL(drm_vram_helper_mode_valid_internal);
Anyway, patch looks good (with the nits addressed one way or the other):
Reviewed-by: Daniel Vetter <daniel.vetter@xxxxxxxx>
> +
> +/**
> + * drm_vram_helper_mode_valid - Tests if a display mode's
> + * framebuffer fits into the available video memory.
> + * @dev: the DRM device
> + * @mode: the mode to test
> + * Returns:
> + * MODE_OK the display mode is supported, or an error code of type
> + * enum drm_mode_status otherwise.
> + *
> + * This function is a variant of drm_vram_helper_mode_valid_internal()
> + * for framebuffers that use at most 32-bit color depth. It can be plugged
> + * directly into struct drm_mode_config_funcs.mode_valid.
> + */
> +enum drm_mode_status
> +drm_vram_helper_mode_valid(struct drm_device *dev,
> + const struct drm_display_mode *mode)
> +{
> + static const unsigned long max_bpp = 4; /* DRM_FORMAT_XRGBA8888 */
> +
> + return drm_vram_helper_mode_valid_internal(dev, mode, max_bpp);
> +}
> +EXPORT_SYMBOL(drm_vram_helper_mode_valid);
> diff --git a/include/drm/drm_gem_vram_helper.h b/include/drm/drm_gem_vram_helper.h
> index 573e9fd109bf..e7d9144c79ad 100644
> --- a/include/drm/drm_gem_vram_helper.h
> +++ b/include/drm/drm_gem_vram_helper.h
> @@ -6,6 +6,7 @@
> #include <drm/drm_file.h>
> #include <drm/drm_gem.h>
> #include <drm/drm_ioctl.h>
> +#include <drm/drm_modes.h>
> #include <drm/ttm/ttm_bo_api.h>
> #include <drm/ttm/ttm_bo_driver.h>
> #include <drm/ttm/ttm_placement.h>
> @@ -205,4 +206,17 @@ struct drm_vram_mm *drm_vram_helper_alloc_mm(
> struct drm_device *dev, uint64_t vram_base, size_t vram_size);
> void drm_vram_helper_release_mm(struct drm_device *dev);
>
> +/*
> + * Mode-config helpers
> + */
> +
> +enum drm_mode_status
> +drm_vram_helper_mode_valid_internal(struct drm_device *dev,
> + const struct drm_display_mode *mode,
> + unsigned long max_bpp);
> +
> +enum drm_mode_status
> +drm_vram_helper_mode_valid(struct drm_device *dev,
> + const struct drm_display_mode *mode);
> +
> #endif
> --
> 2.25.0
>
--
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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