From 1148836fd3226c20de841084aba24184d4fbbe77 Mon Sep 17 00:00:00 2001 From: Helge Deller Date: Wed, 2 Feb 2022 14:55:29 +0100 Subject: Revert "fbdev: Garbage collect fbdev scrolling acceleration, part 1 (from TODO list)" This reverts commit b3ec8cdf457e5e63d396fe1346cc788cf7c1b578. Revert the second (of 2) commits which disabled scrolling acceleration in fbcon/fbdev. It introduced a regression for fbdev-supported graphic cards because of the performance penalty by doing screen scrolling by software instead of using the existing graphic card 2D hardware acceleration. Console scrolling acceleration was disabled by dropping code which checked at runtime the driver hardware capabilities for the BINFO_HWACCEL_COPYAREA or FBINFO_HWACCEL_FILLRECT flags and if set, it enabled scrollmode SCROLL_MOVE which uses hardware acceleration to move screen contents. After dropping those checks scrollmode was hard-wired to SCROLL_REDRAW instead, which forces all graphic cards to redraw every character at the new screen position when scrolling. This change effectively disabled all hardware-based scrolling acceleration for ALL drivers, because now all kind of 2D hardware acceleration (bitblt, fillrect) in the drivers isn't used any longer. The original commit message mentions that only 3 DRM drivers (nouveau, omapdrm and gma500) used hardware acceleration in the past and thus code for checking and using scrolling acceleration is obsolete. This statement is NOT TRUE, because beside the DRM drivers there are around 35 other fbdev drivers which depend on fbdev/fbcon and still provide hardware acceleration for fbdev/fbcon. The original commit message also states that syzbot found lots of bugs in fbcon and thus it's "often the solution to just delete code and remove features". This is true, and the bugs - which actually affected all users of fbcon, including DRM - were fixed, or code was dropped like e.g. the support for software scrollback in vgacon (commit 973c096f6a85). So to further analyze which bugs were found by syzbot, I've looked through all patches in drivers/video which were tagged with syzbot or syzkaller back to year 2005. The vast majority fixed the reported issues on a higher level, e.g. when screen is to be resized, or when font size is to be changed. The few ones which touched driver code fixed a real driver bug, e.g. by adding a check. But NONE of those patches touched code of either the SCROLL_MOVE or the SCROLL_REDRAW case. That means, there was no real reason why SCROLL_MOVE had to be ripped-out and just SCROLL_REDRAW had to be used instead. The only reason I can imagine so far was that SCROLL_MOVE wasn't used by DRM and as such it was assumed that it could go away. That argument completely missed the fact that SCROLL_MOVE is still heavily used by fbdev (non-DRM) drivers. Some people mention that using memcpy() instead of the hardware acceleration is pretty much the same speed. But that's not true, at least not for older graphic cards and machines where we see speed decreases by factor 10 and more and thus this change leads to console responsiveness way worse than before. That's why the original commit is to be reverted. By reverting we reintroduce hardware-based scrolling acceleration and fix the performance regression for fbdev drivers. There isn't any impact on DRM when reverting those patches. Signed-off-by: Helge Deller Acked-by: Geert Uytterhoeven Acked-by: Sven Schnelle Cc: stable@vger.kernel.org # v5.16+ Signed-off-by: Helge Deller Signed-off-by: Daniel Vetter Link: https://patchwork.freedesktop.org/patch/msgid/20220202135531.92183-2-deller@gmx.de --- drivers/video/fbdev/core/fbcon_ud.c | 37 +++++++++++++++++++++++++++++-------- 1 file changed, 29 insertions(+), 8 deletions(-) (limited to 'drivers/video/fbdev/core/fbcon_ud.c') diff --git a/drivers/video/fbdev/core/fbcon_ud.c b/drivers/video/fbdev/core/fbcon_ud.c index 09619bd8e021..8d5e66b1bdfb 100644 --- a/drivers/video/fbdev/core/fbcon_ud.c +++ b/drivers/video/fbdev/core/fbcon_ud.c @@ -44,13 +44,33 @@ static void ud_update_attr(u8 *dst, u8 *src, int attribute, } } + +static void ud_bmove(struct vc_data *vc, struct fb_info *info, int sy, + int sx, int dy, int dx, int height, int width) +{ + struct fbcon_ops *ops = info->fbcon_par; + struct fb_copyarea area; + u32 vyres = GETVYRES(ops->p->scrollmode, info); + u32 vxres = GETVXRES(ops->p->scrollmode, info); + + area.sy = vyres - ((sy + height) * vc->vc_font.height); + area.sx = vxres - ((sx + width) * vc->vc_font.width); + area.dy = vyres - ((dy + height) * vc->vc_font.height); + area.dx = vxres - ((dx + width) * vc->vc_font.width); + area.height = height * vc->vc_font.height; + area.width = width * vc->vc_font.width; + + info->fbops->fb_copyarea(info, &area); +} + static void ud_clear(struct vc_data *vc, struct fb_info *info, int sy, int sx, int height, int width) { + struct fbcon_ops *ops = info->fbcon_par; struct fb_fillrect region; int bgshift = (vc->vc_hi_font_mask) ? 13 : 12; - u32 vyres = info->var.yres; - u32 vxres = info->var.xres; + u32 vyres = GETVYRES(ops->p->scrollmode, info); + u32 vxres = GETVXRES(ops->p->scrollmode, info); region.color = attr_bgcol_ec(bgshift,vc,info); region.dy = vyres - ((sy + height) * vc->vc_font.height); @@ -142,8 +162,8 @@ static void ud_putcs(struct vc_data *vc, struct fb_info *info, u32 mod = vc->vc_font.width % 8, cnt, pitch, size; u32 attribute = get_attribute(info, scr_readw(s)); u8 *dst, *buf = NULL; - u32 vyres = info->var.yres; - u32 vxres = info->var.xres; + u32 vyres = GETVYRES(ops->p->scrollmode, info); + u32 vxres = GETVXRES(ops->p->scrollmode, info); if (!ops->fontbuffer) return; @@ -239,8 +259,8 @@ static void ud_cursor(struct vc_data *vc, struct fb_info *info, int mode, int attribute, use_sw = vc->vc_cursor_type & CUR_SW; int err = 1, dx, dy; char *src; - u32 vyres = info->var.yres; - u32 vxres = info->var.xres; + u32 vyres = GETVYRES(ops->p->scrollmode, info); + u32 vxres = GETVXRES(ops->p->scrollmode, info); if (!ops->fontbuffer) return; @@ -390,8 +410,8 @@ static int ud_update_start(struct fb_info *info) { struct fbcon_ops *ops = info->fbcon_par; int xoffset, yoffset; - u32 vyres = info->var.yres; - u32 vxres = info->var.xres; + u32 vyres = GETVYRES(ops->p->scrollmode, info); + u32 vxres = GETVXRES(ops->p->scrollmode, info); int err; xoffset = vxres - info->var.xres - ops->var.xoffset; @@ -409,6 +429,7 @@ static int ud_update_start(struct fb_info *info) void fbcon_rotate_ud(struct fbcon_ops *ops) { + ops->bmove = ud_bmove; ops->clear = ud_clear; ops->putcs = ud_putcs; ops->clear_margins = ud_clear_margins; -- cgit From a3f781a9d6114c1d1e01defb7aa234dec45d2a5f Mon Sep 17 00:00:00 2001 From: Helge Deller Date: Wed, 2 Feb 2022 14:55:31 +0100 Subject: fbcon: Add option to enable legacy hardware acceleration Add a config option CONFIG_FRAMEBUFFER_CONSOLE_LEGACY_ACCELERATION to enable bitblt and fillrect hardware acceleration in the framebuffer console. If disabled, such acceleration will not be used, even if it is supported by the graphics hardware driver. If you plan to use DRM as your main graphics output system, you should disable this option since it will prevent compiling in code which isn't used later on when DRM takes over. For all other configurations, e.g. if none of your graphic cards support DRM (yet), DRM isn't available for your architecture, or you can't be sure that the graphic card in the target system will support DRM, you most likely want to enable this option. In the non-accelerated case (e.g. when DRM is used), the inlined fb_scrollmode() function is hardcoded to return SCROLL_REDRAW and as such the compiler is able to optimize much unneccesary code away. In this v3 patch version I additionally changed the GETVYRES() and GETVXRES() macros to take a pointer to the fbcon_display struct. This fixes the build when console rotation is enabled and helps the compiler again to optimize out code. Signed-off-by: Helge Deller Cc: stable@vger.kernel.org # v5.10+ Signed-off-by: Helge Deller Signed-off-by: Daniel Vetter Link: https://patchwork.freedesktop.org/patch/msgid/20220202135531.92183-4-deller@gmx.de --- drivers/video/fbdev/core/fbcon_ud.c | 20 ++++++++++---------- 1 file changed, 10 insertions(+), 10 deletions(-) (limited to 'drivers/video/fbdev/core/fbcon_ud.c') diff --git a/drivers/video/fbdev/core/fbcon_ud.c b/drivers/video/fbdev/core/fbcon_ud.c index 8d5e66b1bdfb..23bc045769d0 100644 --- a/drivers/video/fbdev/core/fbcon_ud.c +++ b/drivers/video/fbdev/core/fbcon_ud.c @@ -50,8 +50,8 @@ static void ud_bmove(struct vc_data *vc, struct fb_info *info, int sy, { struct fbcon_ops *ops = info->fbcon_par; struct fb_copyarea area; - u32 vyres = GETVYRES(ops->p->scrollmode, info); - u32 vxres = GETVXRES(ops->p->scrollmode, info); + u32 vyres = GETVYRES(ops->p, info); + u32 vxres = GETVXRES(ops->p, info); area.sy = vyres - ((sy + height) * vc->vc_font.height); area.sx = vxres - ((sx + width) * vc->vc_font.width); @@ -69,8 +69,8 @@ static void ud_clear(struct vc_data *vc, struct fb_info *info, int sy, struct fbcon_ops *ops = info->fbcon_par; struct fb_fillrect region; int bgshift = (vc->vc_hi_font_mask) ? 13 : 12; - u32 vyres = GETVYRES(ops->p->scrollmode, info); - u32 vxres = GETVXRES(ops->p->scrollmode, info); + u32 vyres = GETVYRES(ops->p, info); + u32 vxres = GETVXRES(ops->p, info); region.color = attr_bgcol_ec(bgshift,vc,info); region.dy = vyres - ((sy + height) * vc->vc_font.height); @@ -162,8 +162,8 @@ static void ud_putcs(struct vc_data *vc, struct fb_info *info, u32 mod = vc->vc_font.width % 8, cnt, pitch, size; u32 attribute = get_attribute(info, scr_readw(s)); u8 *dst, *buf = NULL; - u32 vyres = GETVYRES(ops->p->scrollmode, info); - u32 vxres = GETVXRES(ops->p->scrollmode, info); + u32 vyres = GETVYRES(ops->p, info); + u32 vxres = GETVXRES(ops->p, info); if (!ops->fontbuffer) return; @@ -259,8 +259,8 @@ static void ud_cursor(struct vc_data *vc, struct fb_info *info, int mode, int attribute, use_sw = vc->vc_cursor_type & CUR_SW; int err = 1, dx, dy; char *src; - u32 vyres = GETVYRES(ops->p->scrollmode, info); - u32 vxres = GETVXRES(ops->p->scrollmode, info); + u32 vyres = GETVYRES(ops->p, info); + u32 vxres = GETVXRES(ops->p, info); if (!ops->fontbuffer) return; @@ -410,8 +410,8 @@ static int ud_update_start(struct fb_info *info) { struct fbcon_ops *ops = info->fbcon_par; int xoffset, yoffset; - u32 vyres = GETVYRES(ops->p->scrollmode, info); - u32 vxres = GETVXRES(ops->p->scrollmode, info); + u32 vyres = GETVYRES(ops->p, info); + u32 vxres = GETVXRES(ops->p, info); int err; xoffset = vxres - info->var.xres - ops->var.xoffset; -- cgit