[PATCH] [RFC] fbcon: Add option to enable legacy hardware acceleration
Helge Deller
deller at gmx.de
Tue Jan 25 19:17:02 UTC 2022
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...
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
>
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