[PATCH] [RFC] fbcon: Add option to enable legacy hardware acceleration
Helge Deller
deller at gmx.de
Tue Jan 25 19:43:27 UTC 2022
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.
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
>>
>
More information about the dri-devel
mailing list