drm/fb-helper: Add multi buffer support for cma fbdev (5f152576) · Commits · 戴 / test

This patch add a config to support to create multi buffer for cma fbdev. Such as double buffer and triple buffer. Cma fbdev is convient to add a legency fbdev. And still many Android devices use fbdev now and at least double buffer is needed for these Android devices, so that a buffer flip can be operated. It will need some time for Android device vendors to abondon legency fbdev. So multi buffer for fbdev is needed. Signed-off-by:

Xinliang Liu <xinliang.liu@linaro.org> [s.christ@phytec.de: Picking patch from https://lkml.org/lkml/2015/9/14/188 ] Signed-off-by:

Stefan Christ <s.christ@phytec.de> Signed-off-by:

Maxime Ripard <maxime.ripard@free-electrons.com> Acked-by:

Dave Airlie <airlied@gmail.com> Tested-by:

Neil Armstrong <narmstrong@baylibre.com> Signed-off-by:

Daniel Vetter <daniel.vetter@ffwll.ch> Link: http://patchwork.freedesktop.org/patch/msgid/075ffb50cc16ab055b5d47b30163401bb356ab51.1487175046.git-series.maxime.ripard@free-electrons.com

drivers/gpu/drm/Kconfig

+9 −0

Original line number	Diff line number	Diff line
		@@ -99,6 +99,15 @@ config DRM_FBDEV_EMULATION

		If in doubt, say "Y".

		config DRM_FBDEV_OVERALLOC
		int "Overallocation of the fbdev buffer"
		depends on DRM_FBDEV_EMULATION
		default 100
		help
		Defines the fbdev buffer overallocation in percent. Default
		is 100. Typical values for double buffering will be 200,
		triple buffering 300.

		config DRM_LOAD_EDID_FIRMWARE
		bool "Allow to specify an EDID data set instead of probing for it"
		depends on DRM_KMS_HELPER

drivers/gpu/drm/drm_fb_helper.c

+10 −0

Original line number	Diff line number	Diff line
		@@ -48,6 +48,12 @@ module_param_named(fbdev_emulation, drm_fbdev_emulation, bool, 0600);
		MODULE_PARM_DESC(fbdev_emulation,
		"Enable legacy fbdev emulation [default=true]");

		static int drm_fbdev_overalloc = CONFIG_DRM_FBDEV_OVERALLOC;
		module_param(drm_fbdev_overalloc, int, 0444);
		MODULE_PARM_DESC(drm_fbdev_overalloc,
		"Overallocation of the fbdev buffer (%) [default="
		__MODULE_STRING(CONFIG_DRM_FBDEV_OVERALLOC) "]");

		static LIST_HEAD(kernel_fb_helper_list);
		static DEFINE_MUTEX(kernel_fb_helper_lock);

		@@ -1578,6 +1584,10 @@ static int drm_fb_helper_single_fb_probe(struct drm_fb_helper *fb_helper,
		sizes.fb_height = sizes.surface_height = 768;
		}

		/* Handle our overallocation */
		sizes.surface_height *= drm_fbdev_overalloc;
		sizes.surface_height /= 100;

		/* push down into drivers */
		ret = (*fb_helper->funcs->fb_probe)(fb_helper, &sizes);
		if (ret < 0)

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