From: Xinliang Liu <xinliang.liu@xxxxxxxxxx>
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@xxxxxxxxxx>
[s.christ@xxxxxxxxx: Picking patch from
https://lkml.org/lkml/2015/9/14/188]
Signed-off-by: Stefan Christ <s.christ@xxxxxxxxx>
Signed-off-by: Maxime Ripard <maxime.ripard@xxxxxxxxxxxxxxxxxx>
---
drivers/gpu/drm/Kconfig | 9 +++++++++
drivers/gpu/drm/drm_fb_helper.c | 10 ++++++++++
2 files changed, 19 insertions(+), 0 deletions(-)
diff --git a/drivers/gpu/drm/Kconfig b/drivers/gpu/drm/Kconfig
index ebfe8404c25f..700c8b8e57a9 100644
--- a/drivers/gpu/drm/Kconfig
+++ b/drivers/gpu/drm/Kconfig
@@ -84,6 +84,15 @@ 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
diff --git a/drivers/gpu/drm/drm_fb_helper.c b/drivers/gpu/drm/drm_fb_helper.c
index e934b541feea..c6de87abaca8 100644
--- a/drivers/gpu/drm/drm_fb_helper.c
+++ b/drivers/gpu/drm/drm_fb_helper.c
@@ -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);
@@ -1573,6 +1579,10 @@ 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)
--
git-series 0.8.11
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