linux-kernel - Re: [PATCH 03/21] fbcon: Restore fbcon scrolling acceleration

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Message-ID: <CAKMK7uGvOVe8kkJCTkQBEFw+3i2iAMANsyG9vGqZkcROZ9he4A@mail.gmail.com>
Date:   Tue, 1 Feb 2022 11:36:44 +0100
From:   Daniel Vetter <daniel.vetter@...ll.ch>
To:     Helge Deller <deller@....de>
Cc:     DRI Development <dri-devel@...ts.freedesktop.org>,
        Intel Graphics Development <intel-gfx@...ts.freedesktop.org>,
        linux-fbdev@...r.kernel.org, LKML <linux-kernel@...r.kernel.org>,
        stable@...r.kernel.org, Claudio Suarez <cssk@...-c.es>,
        Dave Airlie <airlied@...il.com>,
        Jani Nikula <jani.nikula@...ux.intel.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Pavel Machek <pavel@....cz>, Sam Ravnborg <sam@...nborg.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Javier Martinez Canillas <javierm@...hat.com>,
        Tomi Valkeinen <tomi.valkeinen@...com>,
        Geert Uytterhoeven <geert@...ux-m68k.org>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        Daniel Vetter <daniel.vetter@...el.com>,
        Sven Schnelle <svens@...ckframe.org>,
        Gerd Hoffmann <kraxel@...hat.com>
Subject: Re: [PATCH 03/21] fbcon: Restore fbcon scrolling acceleration

On Tue, Feb 1, 2022 at 11:16 AM Helge Deller <deller@....de> wrote:
>
> On 1/31/22 22:05, Daniel Vetter wrote:
> > This functionally undoes 39aead8373b3 ("fbcon: Disable accelerated
> > scrolling"), but behind the FRAMEBUFFER_CONSOLE_LEGACY_ACCELERATION
> > option.
>
> you have two trivial copy-n-paste errors in this patch which still prevent the
> console acceleration.

Duh :-(

But before we dig into details I think the big picture would be
better. I honestly don't like the #ifdef pile here that much. I wonder
whether your approach, also with GETVX/YRES adjusted somehow, wouldn't
look cleaner? Like I said in the cover letter I got mostly distracted
with fbcon locking last week, not really with this one here at all, so
maybe going with your 4 (or 2 if we squash them like I did here)
patches is neater?

Cheers, Daniel

>
> > diff --git a/drivers/video/fbdev/core/fbcon.c b/drivers/video/fbdev/core/fbcon.c
> > index 2ff90061c7f3..39dc18a5de86 100644
> > --- a/drivers/video/fbdev/core/fbcon.c
> > +++ b/drivers/video/fbdev/core/fbcon.c
> > @@ -1125,13 +1125,15 @@ static void fbcon_init(struct vc_data *vc, int init)
> >
> >       ops->graphics = 0;
> >
> > -     /*
> > -      * No more hw acceleration for fbcon.
> > -      *
> > -      * FIXME: Garbage collect all the now dead code after sufficient time
> > -      * has passed.
> > -      */
> > +#ifdef CONFIG_FRAMEBUFFER_CONSOLE_ROTATION
>
> should be:
> #ifdef CONFIG_FRAMEBUFFER_CONSOLE_LEGACY_ACCELERATION
>
>
> > +     if ((info->flags & FBINFO_HWACCEL_COPYAREA) &&
> > +         !(info->flags & FBINFO_HWACCEL_DISABLED))
> > +             p->scrollmode = SCROLL_MOVE;
> > +     else /* default to something safe */
> > +             p->scrollmode = SCROLL_REDRAW;
> > +#else
> >       p->scrollmode = SCROLL_REDRAW;
> > +#endif
> >
> >       /*
> >        *  ++guenther: console.c:vc_allocate() relies on initializing
> > @@ -1971,15 +1973,49 @@ static void updatescrollmode(struct fbcon_display *p,
> >  {
> >       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,
> > +                           info->fix.xpanstep);
> > +     int ywrap = FBCON_SWAP(ops->rotate, info->fix.ywrapstep, t);
> >       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);
> > +     int good_pan = (cap & FBINFO_HWACCEL_YPAN) &&
> > +             divides(ypan, vc->vc_font.height) && vyres > yres;
> > +     int good_wrap = (cap & FBINFO_HWACCEL_YWRAP) &&
> > +             divides(ywrap, vc->vc_font.height) &&
> > +             divides(vc->vc_font.height, vyres) &&
> > +             divides(vc->vc_font.height, yres);
> > +     int reading_fast = cap & FBINFO_READS_FAST;
> > +     int fast_copyarea = (cap & FBINFO_HWACCEL_COPYAREA) &&
> > +             !(cap & FBINFO_HWACCEL_DISABLED);
> > +     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 ?
> > +                             SCROLL_WRAP_MOVE : SCROLL_PAN_MOVE;
> > +             else
> > +                     p->scrollmode = good_wrap ? SCROLL_REDRAW :
> > +                             SCROLL_PAN_REDRAW;
> > +     } else {
> > +             if (reading_fast || (fast_copyarea && !fast_imageblit))
> > +                     p->scrollmode = SCROLL_MOVE;
> > +             else
> > +                     p->scrollmode = SCROLL_REDRAW;
> > +     }
> > +
> > +#ifndef CONFIG_FRAMEBUFFER_CONSOLE_ROTATION
>
> same here... it needs to be:
> #ifdef CONFIG_FRAMEBUFFER_CONSOLE_LEGACY_ACCELERATION
>
>
> > +     p->scrollmode = SCROLL_REDRAW;
> > +#endif
> >  }
> >
> >  #define PITCH(w) (((w) + 7) >> 3)
> >
>
> still reviewing the other patches...
>
> Helge



-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch