fbcon: Make fbcon a built-time depency for fbdev

There's a bunch of folks who're trying to make printk less
contended and faster, but there's a problem: printk uses the
console_lock, and the console lock has become the BKL for all things
fbdev/fbcon, which in turn pulled in half the drm subsystem under that
lock. That's awkward.

There reasons for that is probably just a historical accident:

- fbcon is a runtime option of fbdev, i.e. at runtime you can pick
  whether your fbdev driver instances are used as kernel consoles.
  Unfortunately this wasn't implemented with some module option, but
  through some module loading magic: As long as you don't load
  fbcon.ko, there's no fbdev console support, but loading it (in any
  order wrt fbdev drivers) will create console instances for all fbdev
  drivers.

- This was implemented through a notifier chain. fbcon.ko enumerates
  all fbdev instances at load time and also registers itself as
  listener in the fbdev notifier. The fbdev core tries to register new
  fbdev instances with fbcon using the notifier.

- On top of that the modifier chain is also used at runtime by the
  fbdev subsystem to e.g. control backlights for panels.

- The problem is that the notifier puts a mutex locking context
  between fbdev and fbcon, which mixes up the locking contexts for
  both the runtime usage and the register time usage to notify fbcon.
  And at runtime fbcon (through the fbdev core) might call into the
  notifier from a printk critical section while console_lock is held.

- This means console_lock must be an outer lock for the entire fbdev
  subsystem, which also means it must be acquired when registering a
  new framebuffer driver as the outermost lock since we might call
  into fbcon (through the notifier) which would result in a locking
  inversion if fbcon would acquire the console_lock from its notifier
  callback (which it needs to register the console).

- console_lock can be held anywhere, since printk can be called
  anywhere, and through the above story, plus drm/kms being an fbdev
  driver, we pull in a shocking amount of locking hiercharchy
  underneath the console_lock. Which makes cleaning up printk really
  hard (not even splitting console_lock into an rwsem is all that
  useful due to this).

There's various ways to address this, but the cleanest would be to
make fbcon a compile-time option, where fbdev directly calls the fbcon
register functions from register_framebuffer, or dummy static inline
versions if fbcon is disabled. Maybe augmented with a runtime knob to
disable fbcon, if that's needed (for debugging perhaps).

But this could break some users who rely on the magic "loading
fbcon.ko enables/disables fbdev framebuffers at runtime" thing, even
if that's unlikely. Hence we must be careful:

1. Create a compile-time dependency between fbcon and fbdev in the
least minimal way. This is what this patch does.

2. Wait at least 1 year to give possible users time to scream about
how we broke their setup. Unlikely, since all distros make fbcon
compile-in, and embedded platforms only compile stuff they know they
need anyway. But still.

3. Convert the notifier to direct functions calls, with dummy static
inlines if fbcon is disabled. We'll still need the fb notifier for the
other uses (like backlights), but we can probably move it into the fb
core (atm it must be built-into vmlinux).

4. Push console_lock down the call-chain, until it is down in
console_register again.

5. Finally start to clean up and rework the printk/console locking.

For context of this saga see

commit 50e244cc793d511b86adea24972f3a7264cae114
Author: Alan Cox <alan@linux.intel.com>
Date:   Fri Jan 25 10:28:15 2013 +1000

    fb: rework locking to fix lock ordering on takeover

plus the pile of commits on top that tried to make this all work
without terminally upsetting lockdep. We've uncovered all this when
console_lock lockdep annotations where added in

commit daee779718a319ff9f83e1ba3339334ac650bb22
Author: Daniel Vetter <daniel.vetter@ffwll.ch>
Date:   Sat Sep 22 19:52:11 2012 +0200

    console: implement lockdep support for console_lock

On the patch itself:
- Switch CONFIG_FRAMEBUFFER_CONSOLE to be a boolean, using the overall
  CONFIG_FB tristate to decided whether it should be a module or
  built-in.

- At first I thought I could force the build depency with just a dummy
  symbol that fbcon.ko exports and fb.ko uses. But that leads to a
  module depency cycle (it works fine when built-in).

  Since this tight binding is the entire goal the simplest solution is
  to move all the fbcon modules (and there's a bunch of optinal
  source-files which are each modules of their own, for no good
  reason) into the overall fb.ko core module. That's a bit more than
  what I would have liked to do in this patch, but oh well.

Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Cc: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Reviewed-by: Sean Paul <seanpaul@chromium.org>
Signed-off-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>

1 files changed, 418 insertions, 0 deletions

diff --git a/drivers/video/fbdev/core/bitblit.c b/drivers/video/fbdev/core/bitblit.c
new file mode 100644
index 000000000000..99f3a1c3d093
--- /dev/null
+++ b/drivers/video/fbdev/core/bitblit.c
@@ -0,0 +1,418 @@
+/*
+ *  linux/drivers/video/console/bitblit.c -- BitBlitting Operation
+ *
+ *  Originally from the 'accel_*' routines in drivers/video/console/fbcon.c
+ *
+ *      Copyright (C) 2004 Antonino Daplas <adaplas @pol.net>
+ *
+ *  This file is subject to the terms and conditions of the GNU General Public
+ *  License.  See the file COPYING in the main directory of this archive for
+ *  more details.
+ */
+
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <linux/string.h>
+#include <linux/fb.h>
+#include <linux/vt_kern.h>
+#include <linux/console.h>
+#include <asm/types.h>
+#include "fbcon.h"
+
+/*
+ * Accelerated handlers.
+ */
+static void update_attr(u8 *dst, u8 *src, int attribute,
+                               struct vc_data *vc)
+{
+        int i, offset = (vc->vc_font.height < 10) ? 1 : 2;
+        int width = DIV_ROUND_UP(vc->vc_font.width, 8);
+        unsigned int cellsize = vc->vc_font.height * width;
+        u8 c;
+
+        offset = cellsize - (offset * width);
+        for (i = 0; i < cellsize; i++) {
+                c = src[i];
+                if (attribute & FBCON_ATTRIBUTE_UNDERLINE && i >= offset)
+                        c = 0xff;
+                if (attribute & FBCON_ATTRIBUTE_BOLD)
+                        c |= c >> 1;
+                if (attribute & FBCON_ATTRIBUTE_REVERSE)
+                        c = ~c;
+                dst[i] = c;
+        }
+}
+
+static void bit_bmove(struct vc_data *vc, struct fb_info *info, int sy,
+                      int sx, int dy, int dx, int height, int width)
+{
+        struct fb_copyarea area;
+
+        area.sx = sx * vc->vc_font.width;
+        area.sy = sy * vc->vc_font.height;
+        area.dx = dx * vc->vc_font.width;
+        area.dy = dy * vc->vc_font.height;
+        area.height = height * vc->vc_font.height;
+        area.width = width * vc->vc_font.width;
+
+        info->fbops->fb_copyarea(info, &area);
+}
+
+static void bit_clear(struct vc_data *vc, struct fb_info *info, int sy,
+                      int sx, int height, int width)
+{
+        int bgshift = (vc->vc_hi_font_mask) ? 13 : 12;
+        struct fb_fillrect region;
+
+        region.color = attr_bgcol_ec(bgshift, vc, info);
+        region.dx = sx * vc->vc_font.width;
+        region.dy = sy * vc->vc_font.height;
+        region.width = width * vc->vc_font.width;
+        region.height = height * vc->vc_font.height;
+        region.rop = ROP_COPY;
+
+        info->fbops->fb_fillrect(info, &region);
+}
+
+static inline void bit_putcs_aligned(struct vc_data *vc, struct fb_info *info,
+                                     const u16 *s, u32 attr, u32 cnt,
+                                     u32 d_pitch, u32 s_pitch, u32 cellsize,
+                                     struct fb_image *image, u8 *buf, u8 *dst)
+{
+        u16 charmask = vc->vc_hi_font_mask ? 0x1ff : 0xff;
+        u32 idx = vc->vc_font.width >> 3;
+        u8 *src;
+
+        while (cnt--) {
+                src = vc->vc_font.data + (scr_readw(s++)&
+                                          charmask)*cellsize;
+
+                if (attr) {
+                        update_attr(buf, src, attr, vc);
+                        src = buf;
+                }
+
+                if (likely(idx == 1))
+                        __fb_pad_aligned_buffer(dst, d_pitch, src, idx,
+                                                image->height);
+                else
+                        fb_pad_aligned_buffer(dst, d_pitch, src, idx,
+                                              image->height);
+
+                dst += s_pitch;
+        }
+
+        info->fbops->fb_imageblit(info, image);
+}
+
+static inline void bit_putcs_unaligned(struct vc_data *vc,
+                                       struct fb_info *info, const u16 *s,
+                                       u32 attr, u32 cnt, u32 d_pitch,
+                                       u32 s_pitch, u32 cellsize,
+                                       struct fb_image *image, u8 *buf,
+                                       u8 *dst)
+{
+        u16 charmask = vc->vc_hi_font_mask ? 0x1ff : 0xff;
+        u32 shift_low = 0, mod = vc->vc_font.width % 8;
+        u32 shift_high = 8;
+        u32 idx = vc->vc_font.width >> 3;
+        u8 *src;
+
+        while (cnt--) {
+                src = vc->vc_font.data + (scr_readw(s++)&
+                                          charmask)*cellsize;
+
+                if (attr) {
+                        update_attr(buf, src, attr, vc);
+                        src = buf;
+                }
+
+                fb_pad_unaligned_buffer(dst, d_pitch, src, idx,
+                                        image->height, shift_high,
+                                        shift_low, mod);
+                shift_low += mod;
+                dst += (shift_low >= 8) ? s_pitch : s_pitch - 1;
+                shift_low &= 7;
+                shift_high = 8 - shift_low;
+        }
+
+        info->fbops->fb_imageblit(info, image);
+
+}
+
+static void bit_putcs(struct vc_data *vc, struct fb_info *info,
+                      const unsigned short *s, int count, int yy, int xx,
+                      int fg, int bg)
+{
+        struct fb_image image;
+        u32 width = DIV_ROUND_UP(vc->vc_font.width, 8);
+        u32 cellsize = width * vc->vc_font.height;
+        u32 maxcnt = info->pixmap.size/cellsize;
+        u32 scan_align = info->pixmap.scan_align - 1;
+        u32 buf_align = info->pixmap.buf_align - 1;
+        u32 mod = vc->vc_font.width % 8, cnt, pitch, size;
+        u32 attribute = get_attribute(info, scr_readw(s));
+        u8 *dst, *buf = NULL;
+
+        image.fg_color = fg;
+        image.bg_color = bg;
+        image.dx = xx * vc->vc_font.width;
+        image.dy = yy * vc->vc_font.height;
+        image.height = vc->vc_font.height;
+        image.depth = 1;
+
+        if (attribute) {
+                buf = kmalloc(cellsize, GFP_ATOMIC);
+                if (!buf)
+                        return;
+        }
+
+        while (count) {
+                if (count > maxcnt)
+                        cnt = maxcnt;
+                else
+                        cnt = count;
+
+                image.width = vc->vc_font.width * cnt;
+                pitch = DIV_ROUND_UP(image.width, 8) + scan_align;
+                pitch &= ~scan_align;
+                size = pitch * image.height + buf_align;
+                size &= ~buf_align;
+                dst = fb_get_buffer_offset(info, &info->pixmap, size);
+                image.data = dst;
+
+                if (!mod)
+                        bit_putcs_aligned(vc, info, s, attribute, cnt, pitch,
+                                          width, cellsize, &image, buf, dst);
+                else
+                        bit_putcs_unaligned(vc, info, s, attribute, cnt,
+                                            pitch, width, cellsize, &image,
+                                            buf, dst);
+
+                image.dx += cnt * vc->vc_font.width;
+                count -= cnt;
+                s += cnt;
+        }
+
+        /* buf is always NULL except when in monochrome mode, so in this case
+           it's a gain to check buf against NULL even though kfree() handles
+           NULL pointers just fine */
+        if (unlikely(buf))
+                kfree(buf);
+
+}
+
+static void bit_clear_margins(struct vc_data *vc, struct fb_info *info,
+                              int bottom_only)
+{
+        unsigned int cw = vc->vc_font.width;
+        unsigned int ch = vc->vc_font.height;
+        unsigned int rw = info->var.xres - (vc->vc_cols*cw);
+        unsigned int bh = info->var.yres - (vc->vc_rows*ch);
+        unsigned int rs = info->var.xres - rw;
+        unsigned int bs = info->var.yres - bh;
+        struct fb_fillrect region;
+
+        region.color = 0;
+        region.rop = ROP_COPY;
+
+        if (rw && !bottom_only) {
+                region.dx = info->var.xoffset + rs;
+                region.dy = 0;
+                region.width = rw;
+                region.height = info->var.yres_virtual;
+                info->fbops->fb_fillrect(info, &region);
+        }
+
+        if (bh) {
+                region.dx = info->var.xoffset;
+                region.dy = info->var.yoffset + bs;
+                region.width = rs;
+                region.height = bh;
+                info->fbops->fb_fillrect(info, &region);
+        }
+}
+
+static void bit_cursor(struct vc_data *vc, struct fb_info *info, int mode,
+                       int softback_lines, int fg, int bg)
+{
+        struct fb_cursor cursor;
+        struct fbcon_ops *ops = info->fbcon_par;
+        unsigned short charmask = vc->vc_hi_font_mask ? 0x1ff : 0xff;
+        int w = DIV_ROUND_UP(vc->vc_font.width, 8), c;
+        int y = real_y(ops->p, vc->vc_y);
+        int attribute, use_sw = (vc->vc_cursor_type & 0x10);
+        int err = 1;
+        char *src;
+
+        cursor.set = 0;
+
+        if (softback_lines) {
+                if (y + softback_lines >= vc->vc_rows) {
+                        mode = CM_ERASE;
+                        ops->cursor_flash = 0;
+                        return;
+                } else
+                        y += softback_lines;
+        }
+
+        c = scr_readw((u16 *) vc->vc_pos);
+        attribute = get_attribute(info, c);
+        src = vc->vc_font.data + ((c & charmask) * (w * vc->vc_font.height));
+
+        if (ops->cursor_state.image.data != src ||
+            ops->cursor_reset) {
+            ops->cursor_state.image.data = src;
+            cursor.set |= FB_CUR_SETIMAGE;
+        }
+
+        if (attribute) {
+                u8 *dst;
+
+                dst = kmalloc(w * vc->vc_font.height, GFP_ATOMIC);
+                if (!dst)
+                        return;
+                kfree(ops->cursor_data);
+                ops->cursor_data = dst;
+                update_attr(dst, src, attribute, vc);
+                src = dst;
+        }
+
+        if (ops->cursor_state.image.fg_color != fg ||
+            ops->cursor_state.image.bg_color != bg ||
+            ops->cursor_reset) {
+                ops->cursor_state.image.fg_color = fg;
+                ops->cursor_state.image.bg_color = bg;
+                cursor.set |= FB_CUR_SETCMAP;
+        }
+
+        if ((ops->cursor_state.image.dx != (vc->vc_font.width * vc->vc_x)) ||
+            (ops->cursor_state.image.dy != (vc->vc_font.height * y)) ||
+            ops->cursor_reset) {
+                ops->cursor_state.image.dx = vc->vc_font.width * vc->vc_x;
+                ops->cursor_state.image.dy = vc->vc_font.height * y;
+                cursor.set |= FB_CUR_SETPOS;
+        }
+
+        if (ops->cursor_state.image.height != vc->vc_font.height ||
+            ops->cursor_state.image.width != vc->vc_font.width ||
+            ops->cursor_reset) {
+                ops->cursor_state.image.height = vc->vc_font.height;
+                ops->cursor_state.image.width = vc->vc_font.width;
+                cursor.set |= FB_CUR_SETSIZE;
+        }
+
+        if (ops->cursor_state.hot.x || ops->cursor_state.hot.y ||
+            ops->cursor_reset) {
+                ops->cursor_state.hot.x = cursor.hot.y = 0;
+                cursor.set |= FB_CUR_SETHOT;
+        }
+
+        if (cursor.set & FB_CUR_SETSIZE ||
+            vc->vc_cursor_type != ops->p->cursor_shape ||
+            ops->cursor_state.mask == NULL ||
+            ops->cursor_reset) {
+                char *mask = kmalloc(w*vc->vc_font.height, GFP_ATOMIC);
+                int cur_height, size, i = 0;
+                u8 msk = 0xff;
+
+                if (!mask)
+                        return;
+
+                kfree(ops->cursor_state.mask);
+                ops->cursor_state.mask = mask;
+
+                ops->p->cursor_shape = vc->vc_cursor_type;
+                cursor.set |= FB_CUR_SETSHAPE;
+
+                switch (ops->p->cursor_shape & CUR_HWMASK) {
+                case CUR_NONE:
+                        cur_height = 0;
+                        break;
+                case CUR_UNDERLINE:
+                        cur_height = (vc->vc_font.height < 10) ? 1 : 2;
+                        break;
+                case CUR_LOWER_THIRD:
+                        cur_height = vc->vc_font.height/3;
+                        break;
+                case CUR_LOWER_HALF:
+                        cur_height = vc->vc_font.height >> 1;
+                        break;
+                case CUR_TWO_THIRDS:
+                        cur_height = (vc->vc_font.height << 1)/3;
+                        break;
+                case CUR_BLOCK:
+                default:
+                        cur_height = vc->vc_font.height;
+                        break;
+                }
+                size = (vc->vc_font.height - cur_height) * w;
+                while (size--)
+                        mask[i++] = ~msk;
+                size = cur_height * w;
+                while (size--)
+                        mask[i++] = msk;
+        }
+
+        switch (mode) {
+        case CM_ERASE:
+                ops->cursor_state.enable = 0;
+                break;
+        case CM_DRAW:
+        case CM_MOVE:
+        default:
+                ops->cursor_state.enable = (use_sw) ? 0 : 1;
+                break;
+        }
+
+        cursor.image.data = src;
+        cursor.image.fg_color = ops->cursor_state.image.fg_color;
+        cursor.image.bg_color = ops->cursor_state.image.bg_color;
+        cursor.image.dx = ops->cursor_state.image.dx;
+        cursor.image.dy = ops->cursor_state.image.dy;
+        cursor.image.height = ops->cursor_state.image.height;
+        cursor.image.width = ops->cursor_state.image.width;
+        cursor.hot.x = ops->cursor_state.hot.x;
+        cursor.hot.y = ops->cursor_state.hot.y;
+        cursor.mask = ops->cursor_state.mask;
+        cursor.enable = ops->cursor_state.enable;
+        cursor.image.depth = 1;
+        cursor.rop = ROP_XOR;
+
+        if (info->fbops->fb_cursor)
+                err = info->fbops->fb_cursor(info, &cursor);
+
+        if (err)
+                soft_cursor(info, &cursor);
+
+        ops->cursor_reset = 0;
+}
+
+static int bit_update_start(struct fb_info *info)
+{
+        struct fbcon_ops *ops = info->fbcon_par;
+        int err;
+
+        err = fb_pan_display(info, &ops->var);
+        ops->var.xoffset = info->var.xoffset;
+        ops->var.yoffset = info->var.yoffset;
+        ops->var.vmode = info->var.vmode;
+        return err;
+}
+
+void fbcon_set_bitops(struct fbcon_ops *ops)
+{
+        ops->bmove = bit_bmove;
+        ops->clear = bit_clear;
+        ops->putcs = bit_putcs;
+        ops->clear_margins = bit_clear_margins;
+        ops->cursor = bit_cursor;
+        ops->update_start = bit_update_start;
+        ops->rotate_font = NULL;
+
+        if (ops->rotate)
+                fbcon_set_rotate(ops);
+}
+
+EXPORT_SYMBOL(fbcon_set_bitops);
+