On Wed, Sep 04, 2019 at 01:56:43PM +0200, Thomas Zimmermann wrote:
The generic fbdev emulation will map and unmap the framebuffer's memory if required. As consoles are most often updated while being on screen, we map the fbdev buffer while it's being displayed. This avoids frequent map/unmap operations in the fbdev code. The original fbdev code in ast used the same trick to improve performance.
v2:
- fix typo in comment
Signed-off-by: Thomas Zimmermann tzimmermann@suse.de Cc: Noralf Trønnes noralf@tronnes.org Cc: Dave Airlie airlied@redhat.com Cc: Greg Kroah-Hartman gregkh@linuxfoundation.org Cc: Thomas Gleixner tglx@linutronix.de Cc: Sam Ravnborg sam@ravnborg.org Cc: Gerd Hoffmann kraxel@redhat.com Cc: Oleksandr Andrushchenko oleksandr_andrushchenko@epam.com Cc: CK Hu ck.hu@mediatek.com Cc: Daniel Vetter daniel.vetter@ffwll.ch Cc: Alex Deucher alexander.deucher@amd.com Cc: "Christian König" christian.koenig@amd.com Cc: YueHaibing yuehaibing@huawei.com Cc: Sam Bobroff sbobroff@linux.ibm.com Cc: Huang Rui ray.huang@amd.com Cc: "Y.C. Chen" yc_chen@aspeedtech.com Cc: Rong Chen rong.a.chen@intel.com Cc: Feng Tang feng.tang@intel.com Cc: Huang Ying ying.huang@intel.com Cc: Davidlohr Bueso dave@stgolabs.net
drivers/gpu/drm/ast/ast_mode.c | 19 +++++++++++++++++++ 1 file changed, 19 insertions(+)
diff --git a/drivers/gpu/drm/ast/ast_mode.c b/drivers/gpu/drm/ast/ast_mode.c index d349c721501c..c10fff652228 100644 --- a/drivers/gpu/drm/ast/ast_mode.c +++ b/drivers/gpu/drm/ast/ast_mode.c @@ -529,13 +529,20 @@ static int ast_crtc_do_set_base(struct drm_crtc *crtc, struct drm_framebuffer *fb, int x, int y, int atomic) {
- struct drm_fb_helper *fb_helper = crtc->dev->fb_helper;
struct drm_framebuffer *fbcon = crtc->dev->fb_helper->buffer->fb ?
makes clear what is going on without excessive commenting ;)
struct drm_gem_vram_object *gbo; int ret; s64 gpu_addr;
void *base;
if (!atomic && fb) { gbo = drm_gem_vram_of_gem(fb->obj[0]); drm_gem_vram_unpin(gbo);
// Unmap fbdev FB if it's not being displayed// any longer.
I'd drop the comment. It says *what* the comment is doing. You should be able to figure by just reading the code. Comments should explain *why* the code does something ...
if (fb == fb_helper->buffer->fb)drm_gem_vram_kunmap(gbo);}
gbo = drm_gem_vram_of_gem(crtc->primary->fb->obj[0]);
@@ -552,6 +559,14 @@ static int ast_crtc_do_set_base(struct drm_crtc *crtc, ast_set_offset_reg(crtc); ast_set_start_address_crt1(crtc, (u32)gpu_addr);
- // Map fbdev FB while it's being displayed. This avoids frequent
- // mapping and unmapping within the fbdev code.
... like this one (avoid frequent map/unmap).
Comments should use /* */ style, especially multi line comments. See also the comment section in Documentation/process/coding-style.rst
cheers, Gerd