[PATCH] [RFC] fbcon: Add option to enable legacy hardware acceleration
Daniel Vetter
daniel at ffwll.ch
Wed Jan 26 11:14:41 UTC 2022
On Tue, Jan 25, 2022 at 8:44 PM Helge Deller <deller at gmx.de> wrote:
>
> On 1/25/22 20:17, Helge Deller wrote:
> > On 1/25/22 20:12, Helge Deller wrote:
> >> 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.
> >>
> >>
> >> This patch is the first RFC.
> >
> > I forgot to mention that by using the static fb_scrollmode() function
> > I expect the compiler to optimize-out all code which seems problematic
> > from DRM's POV...
>
> This patch is not complete, for example there are more changes necessary
> in fbcon_cw.c, bcon_ccw.c and fbcon_ccw.c.
>
> Anyway, for the first round I'm interested in general feedback, if this is
> the direction which is acceptable for you.
>
> In addition I think fb_scrollmode() should be renamed to fbcon_scrollmode()
> to make it clear that it's a fbcon-related function.
I started typing my on flavour of this and wasn't happy with some of
the ifdefs, your fb_scrollmode() takes care of the annoying ones in a
tidy way. I'll include your diff here and I'll try and get my series
sent out today (there's a bunch of random little locking cleanups in
fbcon.c that I've done since the code is just a bit too entertaining
as-is).
Cheers, Daniel
>
> If you want to test this patch you will need to first apply the revert-patches
> I sent earlier.
> Alternatively for testing it's possible to pull from the "fbcon-accel" branch from:
> https://git.kernel.org/pub/scm/linux/kernel/git/deller/linux-fbdev.git fbcon-accel
>
> Helge
>
>
>
> >> Independed of this patch I did some timing experiments with a qemu
> >> virtual machine running a PA-RISC Debian Linux installation with a
> >> screen resolution of 2048x1024 with 8bpp. In that case qemu emulated the
> >> graphics hardware bitblt and fillrect acceleration by using the native
> >> (x86) CPU.
> >>
> >> It was a simple testcase which was to run "time dmesg", where the syslog
> >> had 284 lines. The results showed a huge speedup:
> >> a) time dmesg (without acceleration):
> >> -> 19.0 seconds
> >> b) time dmesg (with acceleration):
> >> -> 2.6 seconds
> >>
> >> Signed-off-by: Helge Deller <deller at gmx.de>
> >>
> >> diff --git a/drivers/video/console/Kconfig b/drivers/video/console/Kconfig
> >> index 840d9813b0bc..da84d1c21c21 100644
> >> --- a/drivers/video/console/Kconfig
> >> +++ b/drivers/video/console/Kconfig
> >> @@ -78,6 +78,17 @@ config FRAMEBUFFER_CONSOLE
> >> help
> >> Low-level framebuffer-based console driver.
> >>
> >> +config FRAMEBUFFER_CONSOLE_LEGACY_ACCELERATION
> >> + bool "Framebuffer Console hardware acceleration support"
> >> + depends on FRAMEBUFFER_CONSOLE
> >> + default y if !DRM
> >> + default y if !(X86 || ARM)
> >> + help
> >> + If you use a system on which DRM is fully supported you usually want to say N,
> >> + otherwise you probably want to enable this option.
> >> + If enabled the framebuffer console will utilize the hardware acceleration
> >> + of your graphics card by using hardware bitblt and fillrect features.
> >> +
> >> config FRAMEBUFFER_CONSOLE_DETECT_PRIMARY
> >> bool "Map the console to the primary display device"
> >> depends on FRAMEBUFFER_CONSOLE
> >> diff --git a/drivers/video/fbdev/core/fbcon.c b/drivers/video/fbdev/core/fbcon.c
> >> index b813985f1403..f7b7d35953e8 100644
> >> --- a/drivers/video/fbdev/core/fbcon.c
> >> +++ b/drivers/video/fbdev/core/fbcon.c
> >> @@ -1136,11 +1136,13 @@ static void fbcon_init(struct vc_data *vc, int init)
> >>
> >> ops->graphics = 0;
> >>
> >> +#ifdef CONFIG_FRAMEBUFFER_CONSOLE_LEGACY_ACCELERATION
> >> if ((cap & FBINFO_HWACCEL_COPYAREA) &&
> >> !(cap & FBINFO_HWACCEL_DISABLED))
> >> p->scrollmode = SCROLL_MOVE;
> >> else /* default to something safe */
> >> p->scrollmode = SCROLL_REDRAW;
> >> +#endif
> >>
> >> /*
> >> * ++guenther: console.c:vc_allocate() relies on initializing
> >> @@ -1705,7 +1707,7 @@ static bool fbcon_scroll(struct vc_data *vc, unsigned int t, unsigned int b,
> >> count = vc->vc_rows;
> >> if (logo_shown >= 0)
> >> goto redraw_up;
> >> - switch (p->scrollmode) {
> >> + switch (fb_scrollmode(p)) {
> >> case SCROLL_MOVE:
> >> fbcon_redraw_blit(vc, info, p, t, b - t - count,
> >> count);
> >> @@ -1795,7 +1797,7 @@ static bool fbcon_scroll(struct vc_data *vc, unsigned int t, unsigned int b,
> >> count = vc->vc_rows;
> >> if (logo_shown >= 0)
> >> goto redraw_down;
> >> - switch (p->scrollmode) {
> >> + switch (fb_scrollmode(p)) {
> >> case SCROLL_MOVE:
> >> fbcon_redraw_blit(vc, info, p, b - 1, b - t - count,
> >> -count);
> >> @@ -1946,12 +1948,12 @@ static void fbcon_bmove_rec(struct vc_data *vc, struct fbcon_display *p, int sy,
> >> height, width);
> >> }
> >>
> >> -static void updatescrollmode(struct fbcon_display *p,
> >> +static void updatescrollmode_accel(struct fbcon_display *p,
> >> struct fb_info *info,
> >> struct vc_data *vc)
> >> {
> >> +#ifdef CONFIG_FRAMEBUFFER_CONSOLE_LEGACY_ACCELERATION
> >> struct fbcon_ops *ops = info->fbcon_par;
> >> - int fh = vc->vc_font.height;
> >> int cap = info->flags;
> >> u16 t = 0;
> >> int ypan = FBCON_SWAP(ops->rotate, info->fix.ypanstep,
> >> @@ -1972,12 +1974,6 @@ static void updatescrollmode(struct fbcon_display *p,
> >> int fast_imageblit = (cap & FBINFO_HWACCEL_IMAGEBLIT) &&
> >> !(cap & FBINFO_HWACCEL_DISABLED);
> >>
> >> - p->vrows = vyres/fh;
> >> - if (yres > (fh * (vc->vc_rows + 1)))
> >> - p->vrows -= (yres - (fh * vc->vc_rows)) / fh;
> >> - if ((yres % fh) && (vyres % fh < yres % fh))
> >> - p->vrows--;
> >> -
> >> if (good_wrap || good_pan) {
> >> if (reading_fast || fast_copyarea)
> >> p->scrollmode = good_wrap ?
> >> @@ -1991,6 +1987,27 @@ static void updatescrollmode(struct fbcon_display *p,
> >> else
> >> p->scrollmode = SCROLL_REDRAW;
> >> }
> >> +#endif
> >> +}
> >> +
> >> +static void updatescrollmode(struct fbcon_display *p,
> >> + struct fb_info *info,
> >> + struct vc_data *vc)
> >> +{
> >> + struct fbcon_ops *ops = info->fbcon_par;
> >> + int fh = vc->vc_font.height;
> >> + int yres = FBCON_SWAP(ops->rotate, info->var.yres, info->var.xres);
> >> + int vyres = FBCON_SWAP(ops->rotate, info->var.yres_virtual,
> >> + info->var.xres_virtual);
> >> +
> >> + p->vrows = vyres/fh;
> >> + if (yres > (fh * (vc->vc_rows + 1)))
> >> + p->vrows -= (yres - (fh * vc->vc_rows)) / fh;
> >> + if ((yres % fh) && (vyres % fh < yres % fh))
> >> + p->vrows--;
> >> +
> >> + /* update scrollmode in case hardware acceleration is used */
> >> + updatescrollmode_accel(p, info, vc);
> >> }
> >>
> >> #define PITCH(w) (((w) + 7) >> 3)
> >> @@ -2148,7 +2165,7 @@ static int fbcon_switch(struct vc_data *vc)
> >>
> >> updatescrollmode(p, info, vc);
> >>
> >> - switch (p->scrollmode) {
> >> + switch (fb_scrollmode(p)) {
> >> case SCROLL_WRAP_MOVE:
> >> scrollback_phys_max = p->vrows - vc->vc_rows;
> >> break;
> >> diff --git a/drivers/video/fbdev/core/fbcon.h b/drivers/video/fbdev/core/fbcon.h
> >> index 9315b360c898..c5c043f38162 100644
> >> --- a/drivers/video/fbdev/core/fbcon.h
> >> +++ b/drivers/video/fbdev/core/fbcon.h
> >> @@ -29,7 +29,9 @@ struct fbcon_display {
> >> /* Filled in by the low-level console driver */
> >> const u_char *fontdata;
> >> int userfont; /* != 0 if fontdata kmalloc()ed */
> >> +#ifdef CONFIG_FRAMEBUFFER_CONSOLE_LEGACY_ACCELERATION
> >> u_short scrollmode; /* Scroll Method */
> >> +#endif
> >> u_short inverse; /* != 0 text black on white as default */
> >> short yscroll; /* Hardware scrolling */
> >> int vrows; /* number of virtual rows */
> >> @@ -208,6 +210,17 @@ static inline int attr_col_ec(int shift, struct vc_data *vc,
> >> #define SCROLL_REDRAW 0x004
> >> #define SCROLL_PAN_REDRAW 0x005
> >>
> >> +static inline u_short fb_scrollmode(struct fbcon_display *fb)
> >> +{
> >> +#ifdef CONFIG_FRAMEBUFFER_CONSOLE_LEGACY_ACCELERATION
> >> + return fb->scrollmode;
> >> +#else
> >> + /* hardcoded to SCROLL_REDRAW if acceleration was disabled. */
> >> + return SCROLL_REDRAW;
> >> +#endif
> >> +}
> >> +
> >> +
> >> #ifdef CONFIG_FB_TILEBLITTING
> >> extern void fbcon_set_tileops(struct vc_data *vc, struct fb_info *info);
> >> #endif
> >>
> >
>
--
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
More information about the dri-devel
mailing list